Muscles + Muscle Tissue (Ch. 9)

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The contractile units of skeletal muscles are ________.

myofibrils

The contractile units of skeletal muscles are? T tubules mitochondria myofibrils microtubules

myofibrils

Which of the following statements is NOT true regarding ATP production in muscles during periods of prolonged energy use, such as exercise?

In the absence of oxygen, creatine phosphate can drive aerobic respiration pathways for a few minutes

The strongest muscle contractions are normally achieved by......?

Increasing the stimulation up to the maximal stimulus

c) Muscle Fiber

Individual muscle fiber. Skeletal and smooth muscle cells (but not cardiac muscle cells) are elongated and called___. a) Epimysium b) Endomysium c) Muscle Fiber d) Fascicle e) Perimysium

What is the functional unit of a skeletal muscle called?

a sarcomere

What is the functional unit of a skeletal muscle called? the sarcoplasmic reticulum a myofibril a sarcomere a myofilament

a sarcomere

Muscle tone is ________. the condition of athletes after intensive training the feeling of well-being following exercise the ability of a muscle to efficiently cause skeletal movements a state of sustained partial contraction

a state of sustained partial contraction

Contractions elicited by a single brief stimulus is called

a twitch

What is the functional unit of a skeletal muscle called? a sarcomere the sarcoplasmic reticulum a myofilament a myofibril

a) a sarcomere

Lactic Acid

made if their is no oxygen present or work is more then you can breathe; pyruvic acid is transformed to lactic acid; made either way by glucose or glycogen; liver can use or send back to be formed to pyruvic

Belly

main mass of the muscle between the origin and the insertion

The stimulus above which no stronger contraction can be elicited, because all motor units are firing in the muscle.

maximal stimulus

Muscle Tone

relaxed muscles that are almost slightly contracted; its due to spinal reflexes that activate first one group of motor units then another in response to activation of stretch receptors in muscles

Excitation-contraction coupling includes all EXCEPT which of the following events?

release of ACh from axon terminals at the neuromuscular junction

Muscle Twitch

response of a motor neuron to a single action potential of its motor neuron

Which muscle cells have the greatest ability to regenerate?

smooth

Oxygen starved tissues can release chemical signals into the blood that can change the diameter of nearby blood vessels delivering oxygen and nutrients to the tissues. In doing so the blood vessels will respond through vasodilation (widening of the vessel). Which muscle type is responsible for this vasodilation?

smooth muscle

isotonic contraction

-muscle shortens because muscle tension exceeds load -muscle develops enough tension (force)to lift the load (weight)

True/False: Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments.

True

What is the reason for skeletal muscle striation?

Because of A & I bands

Which of the following is most directly required to initiate the coupling of the myosin to actin?

Ca+

Troponin

Calcium attaches to Troponin; alters shape of Troponin&changes the position of tropomyosin

What is the role of calcium in the cross bridge cycle?

Calcium binds to troponin, altering its shape.

What specific event triggers the uncovering of the myosin binding site on actin?

Calcium ions bind to troponin and change its shape

Which of the following is most directly required to initiate the coupling of myosin to actin?

Calcium ions. Ca2+ binds to troponin, which removes tropomyosin from the myosin binding site on actin

Which type of muscle tissue has the longest refractory period?

Cardiac Muscles

size principle (motor unit recruitment)

-Motor units with smallest muscle fibers are recruited first -Motor units with larger and larger fibers are recruited as stimulus intensity increases -Largest motor units are activated only for most powerful contractions -Motor units in muscle usually contract asynchronously

ATP supplies the energy needed for the muscle fiber to

-Move and detach cross bridges -Pump calcium back into SR -Pump Na+ out of and K+ back into cell after excitation-contraction coupling

dystrophin and DMD

-a cytoplasmic protein that links the cytoskeleton to the extracellular matrix, stabilizing the sarcolemma -Fragile sarcolemma tears during contractions, causing entry of excessCa2+

period of contraction

-cross bridge formation; tension increases -2nd phase of muscle twitch

What controls the force of muscle contraction? A) wave summation B) multimotor unit summation C) treppe D) concentric contractions

B) multimotor unit summation

Muscle tissue has all of the following properties except ________. excitability secretion extensibility contractility

B. secretion

smooth muscle

-Found in walls of hollow organs: stomach, urinary bladder, and airways -Not striated, Involuntary -Produces slow sustained contractions

cardiac muscle

-Found only in heart: Makes up bulk of heart walls -Contracts at steady rate due to heart's own pacemaker, but nervous system can increase rate -Key words: cardiac, striated, and involuntary -cells called muscle cells (not fibers)

fused (complete) tetanus

-If stimuli frequency increases, muscle tension reaches maximum -contractions "fuse" into one smooth sustained contraction plateau -prolonged contractions lead to muscle fatigue

B) Fast (oxidative or glycolytic), fatigable fibers -glycogen - one form in which body fuel is stored. -Stored primarily in liver and broken down into glucose when needed by the body.

Contain abundant amounts of glycogen. A) Slow (oxidative), fatigue-resistant fibers B) Fast (oxidative or glycolytic), fatigable fibers

A) Tetanus -tetan = rigid -A state of continuous muscular contraction, especially when induced artificially by rapidly repeated stimuli.

Continued sustained smooth contraction due to rapid stimulation. A) Tetanus B) Wave summation C) Muscle Tone D) Multiple motor unit summation E) Maximal stimulus

Why should you warm up before a race?

Creates more efficient cross bridges leading to better muscle contraction

What happens to the H Zone during a contraction?

DISSAPEARS!!!=0=0=0

What happens to the I band during a contraction?

Decreases in length

A) Slow (oxidative), fatigue-resistant fibers

Depends on oxygen delivery and aerobic mechanisms. A) Slow (oxidative), fatigue-resistant fibers B) Fast (oxidative or glycolytic), fatigable fibers

True

Muscle tension remains relatively constant during isotonic contraction.

Which term best identifies a muscle cell? muscle fiber muscle fascicle myofibril sarcomere

a) muscle fiber

maximal stimulus

all motor units are firing, no more contraction can occur above this stimulus

A muscle that opposes, or reverses, a particular movement is a(n) ________.

antagonist

difference in twitch strength and duration

are due to variations in metabolic properties and enzymes between muscles

multi unit smooth muscle

arrector pili muscles, large airways to lungs, large arteries, rare gap junction

Identify the correct sequence of the following events. (a) Myosin generates a power stroke. (b) Ca+ binds to troponin. (c) ATP recharges the myosin head. (d) Troponin removes tropomyosin from G actin. (e) The sarcomere shortens. (f) Myosin binds to actin

b,d,f,a,e,c

bdfaec

period of relaxation

calcium reenters into SR; no muscle contraction

Transverse Tubule

carries impulse deep into the core of a muscle fiber

refractory period

cell cannot be stimulated again until repolarization is complete

Which of the following is true about smooth muscle?

certain smooth muscle cells can actually divide to increase their numbers

In an isotonic contraction, the muscle ________.

changes in length and moves the "load"

Acetylcholine receptors are best characterized as what type of channel?

chemically gated Na+-K+ channels

muscle tone

continuous contraction even when muscle is at rest

The oxygen-binding protein found in muscle cells is

myoglobin

The oxygen-binding protein found in muscle cells is ________.

myoglobin

The oxygen-binding protein found in muscle cells is ________. myoglobin ATP hemoglobin immunoglobin

myoglobin

The thicker filaments are the ________ filaments.

myosin

Which protein is indicated by the letter E? (see figure 4) troponin myosin actin tropomyosin

myosin

Which protein inhibits interaction between actin and myosin to prevent skeletal muscle contraction; and which ions remove the inhibition?

tropomysin, calcium ions

A contraction in which the muscle does not shorten but its tension increases is called isometric contraction.

true

A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell.

true

An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, sliding stops.

true

One of the functions of skeletal muscle contraction is production of heat.

true

Thick Filaments

(Myosin) composed of a tail&double head region

Sacroplasmic reticulum

"Endoplasmic Reticulum" of a muscle cell; calcium ions are resting

Thin Filaments

(Actin) Troponin&Tropomyosin attached to it

4 steps to cross bridge formation

1. Cross bridge formation: high-energy myosin head attaches to actin thin filament active site 2.Working (power) stroke: myosin head pivots and pulls thin filament toward M line 3.Cross bridge detachment: ATP attaches to myosin head, causing cross bridge to detach 4.Cocking of myosin head: energy from hydrolysis of ATP "cocks" myosin head into high-energy state

contraction overview

1. Nerve impulse reaches the end of an axon, Ca2+ channels open and Ca2+enters the axon 2.Synaptic vesicles to fuse with the axonal membrane, Ach is released into the synaptic cleft via exocytosis, ACh diffuses across the synaptic cleft and binds to receptors on the sarcolemma 3. Na chanels open causing the motor end plate to depolarize-If depolarized to threshold (-50 to -55) an action potential is generated down the sarcolemma and t-tubules 4. Ca2+is released from terminal cisternae 5. Ca2+causes troponin/tropomyosin to be released from active site of actin, Myosin head creates a cross bridge with actin = contraction 6. After action potential ACh is destroyed by the enzyme acetylcholinesterase 7. Membrane Repolarization (Na channels close, K channels open) and Na/K pump (restores ionic concentrations), Ca2+is removed from the muscle fiber and contraction ends

4 steps for skeletal muscle contraction

1. Nerve stimulation (NMJ) 2.Action potential, an electrical current, must be generated in sarcolemma (NMJ) 3. Action potential must be propagated along sarcolemma (excitation-contraction coupling) 4. Intracellular Ca2+ levels must rise briefly (excitation-contraction coupling)

factors that affect number of cross bridges attached

1. Number of muscle fibers stimulated (recruitment) 2. Relative size of fibers: the bulkier the muscle, the more tension it can develop 3. Frequency of stimulation 4. Degree of muscle stretch

After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?

AChe destroying the ACh

Which event causes cross bridge detachment?

ATP binding to myosin head

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?

ATP binds to the myosin head.

destroys ACh

Acetylcholinesterase

Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________. A) cross bridge attachment would be optimum because of all the free binding sites on actin B) no muscle tension could be generated C) maximum force production would result because the muscle has a maximum range of travel D) ATP consumption would increase because the sarcomere is "trying" to contract

B) no muscle tension could be generated

When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods? A) relaxation period B) refractory period C) latent period D) fatigue period

B) refractory period

The muscle cell membrane is called the ________. A) endomysium B) sarcolemma C) perimysium D) epimysium

B) sarcolemma

What produces the striations of a skeletal muscle cell? A) a difference in the thickness of the sarcolemma B) the arrangement of myofilaments C) the sarcoplasmic reticulum D) the T tubules

B) the arrangement of myofilaments

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment? Acetylcholine binds to receptors in the junctional folds of the sarcolemma. ADP and inorganic phosphate are bound to the myosin head. ATP binds to the myosin head. Calcium ions bind to troponin.

C)ATP binds to the myosin head. The binding of ATP to the myosin head weakens the bond between myosin and actin, forcing the myosin head to detach. ATP also provides the energy for the next power stroke.

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber? Calcium ions are stored in the nuclei. Calcium ions are stored in the transverse tubules. Calcium ions are stored in the sarcoplasmic reticulum. Calcium ions are stored in the mitochondria.

C)Calcium ions are stored in the sarcoplasmic reticulum. Yes! Sarcoplasmic reticulum is the specific name given to the smooth endoplasmic reticulum in muscle fibers. The sarcoplasmic reticulum is very elaborate in skeletal muscle fibers, allowing for significant storage of calcium ions.`

e) M line -(from the German "Mittel", middle of the sarcomere).

Inside the H-zone is a thin ___. a) Z disc b) H zone c) I band d) A band e) M line

C) Muscle Tone -All skeletal muscle is maintained in a constant, slightly contracted state - spinal reflexes activate groups of motor units alternately

Determined by alternating motor units of a muscle organ even when the muscle is at rest. A) Tetanus B) Wave summation C) Muscle Tone D) Multiple motor unit summation E) Maximal stimulus

Duchenne muscular dystrophy could theoretically be cured if a technique was developed that would _________.

Duchenne muscular dystrophy is caused by a mutation in the dystrophin gene. Without a normal copy of DNA for transcription, there can never be a normal protein translated. This genetic mutation causes the protein to be either abnormal in structure or completely absent.

During muscle contraction, myosin cross bridges attach to which active sites? a) thick filaments b) Z discs c) actin filaments d) myosin filaments

action potential steps (2nd step of skeletal muscle contraction)

End plate potential, Depolarization, Repolarization

The connective tissue covering that encloses the sarcolemma of an individual muscle fiber is called

Endomysium

Which of the following surrounds the individual muscle cell? perimysium fascicle endomysium epimysium

Endomysium

What is the functional role of the T tubules?

Enhance cellular communication during muscle contraction

Name the connective tissue covering in order superficial to deep of skeletal muscles

Epimysium (outer covering around a muscle organ) Permysium(outer covering around a bundle of muscle fibers) endomysium (C.T. located between individual muscle fibers)

A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate.

False

During isometric contraction, the energy used appears as movement

False

A muscle that immobilizes one or more bone to act on a stable base

Fixator

d) A band -(for anisotropic). Named for their properties under a polarizing microscope. -Anisotropic is the property of being directionally dependent, as opposed to isotropy, which implies identical properties in all directions. -Thick and thin filaments overlap.

Following the I-band is the ___. a) Z disc b) H zone c) I band d) A band e) M line

Sacromere

Functional unit of contraction in skeletal muscle fiber; Shorten when myosin heads in thick myofilaments form cross bridges with actin molecules in thin myofilaments

An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.

Glycolysis

B) Fast (oxidative or glycolytic), fatigable fibers

Have very fast-acting myosin ATPases and depend upon anaerobic metabolism during contraction. A) Slow (oxidative), fatigue-resistant fibers B) Fast (oxidative or glycolytic), fatigable fibers

D) Multiple motor unit summation -The force of contraction is controlled more precisely by recruitment also called multiple motor unit summation.

How a smooth increase in muscle force is produced. A) Tetanus B) Wave summation C) Muscle Tone D) Multiple motor unit summation E) Maximal stimulus

Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________. a) cross bridge attachment would be optimum because of all the free binding sites on actin b) ATP consumption would increase because the sarcomere is "trying" to contract c) maximum force production would result because the muscle has a maximum range of travel d) no muscle tension could be generated

2. The------- contains only the actin filaments.

I band

The ________ contains only the actin filaments.

I band

Which of the following best describes the orbicularis oris?

It closes, purses, and protrudes the lips.

If the cell could no longer produce ATP, what would be the effect on the sarcoplasmic reticulum?

It would be unable to concentrate Ca+ in the sarcoplasmic reticulum

f the cell could no longer produce ATP, what would be the effect on the sarcoplasmic reticulum?

It would be unable to concentrate Ca+ in the sarcoplasmic reticulum.

What band is the I band?

Just Actin

What composes the H Zone?

Just myosin?

During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________.

Lactic acid

pyruvic acid converts to _____________during intense exercise

Lactic acid

Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the events of excitation-contraction coupling occur.

Latent

aerobic endurance

Length of time muscle contracts using aerobic pathways

dystrophin

Links thin filaments to proteins of sarcolemma (plasma membrane of muscle fiber)

Motor Neuron and all the muscles cells it innervates

Motor Unit

Aerobic pathway

Red fibers, marathons

Which of the following is true? a. Smooth muscle lacks the thin and thick filaments characteristic of skeletal muscle. b. Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not. c. Skeletal muscle lacks the coarse connective tissue sheaths that are found in smooth muscle. d. Skeletal muscle fibers tend to be shorter than smooth muscle fibers.

Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not

Of the following items listed below, which is the best description for why skeletal muscle stores glycogen.

Skeletal muscle is a heavy consumer of energy.

Which muscle cells have the greatest ability to regenerate?

Smooth

c) I band -I-band (for isotropic) -Isotropy is uniformity in all directions; it is derived fromt he Greek iso (equal) and tropos (direction). -Thin filaments only.

Surrounding the Z-line is the region of the ___. a) Z disc b) H zone c) I band d) A band e) M line

A muscle that assist the action of the prime mover

Synergist

A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell. True False

TRUE

TRUE OR FALSE Bones act as levers for the muscles

TRUE

TRUE OR FALSE Calcium ions bind to troponin and change its shape

TRUE

TRUE OR FALSE Muscle Tone is a sustained partial contraction

TRUE

TRUE OR FALSE Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not.

TRUE

TRUE OR FALSE The broadest muscle on the back is the latissimus dorsi

TRUE

The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily. True False

TRUE

A cord or ropelike piece of DFCT (Dense Fibrous Connective Tissue) that attached muscle to bone

Tendon

Isometric

Tension increases but force does not overcome the load. NO MUSCLE CONTRACTION

2 and 6 The A band, also know as the dark band, is occupied by the entire length of thick myofilaments.

The region between which two points corresponds to the entire A (dark) band? 1 and 2 2 and 6 2 and 3 3 and 5

What structure in skeletal muscle cells functions in calcium storage?

sarcoplasmic reticulum

Which organelle can chemically regulate the shortening of the muscle?

sarcoplasmic reticulum

Which of the following is NOT a normal function of muscle tissue?

secreting hormones

Muscle tissue has all of the following properties except ________.

secretion

Motor Nerve

served each muscle; each motor nerve contains axons of up to hundreds of motor neurons

muscle twitch

simple contraction of one motor unit

Which type of muscle requires voluntary nervous stimulation for activation?

skeletal

Which of the following are correctly paired? cardiac muscle; nonstriated cardiac muscle; voluntary control skeletal muscle; voluntary control smooth muscle; striated

skeletal muscle; voluntary control

A relatively high percentage are found in successful marathon runners.

slow (oxidative fatigue resistant fibers)

Abundant in muscles used to maintain posture.

slow (oxidative fatigue resistant fibers)

Depends on oxygen delivery and aerobic mechanisms

slow (oxidative fatigue resistant fibers)

Anaerobic pathway

sprinting

A muscle that opposes the action of a prime mover

Antagonist

The thin filaments (actin) contain a polypeptide subunit G actin that bear active sites for myosin attachment.

True

What happens in Rigor Mortis

Not ATP released- actin and myosin can't disengage

Carries an impulse deep into the core of a muscle fiber

Tranverse Tubules

A sarcomere is the distance between-------two .

Z discs

Contain abundant amounts of glycogen.

fast (oxidative or gylcolytic fatigable fibers)

unitary smooth muscle cell

visceral

The buccinator muscle compresses the cheek and is well developed in nursing infants.

true

True/False: A contraction in which the muscle does not shorten but its tension increases is called isometric contraction.

True

True/False: A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell.

True

load

-muscles contract fastest when no load is added -The greater the load, the shorter the duration of contraction -The greater the load, the slower the contraction

True/False: An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, sliding stops.

True

True/False: Cardiac muscle has a limited regenerative capacity

True

True/False: Cells of unitary smooth muscle are found in the longitudinal and circular muscle layers of the intestine.

True

True/False: Eccentric contractions are more forceful than concentric contractions.

True

True/False: Muscle cells store more creatine phosphate than ATP resulting in the muscle having a reserve source of energy.

True

True/False: Muscle tone is the small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units.

True

motor unit

-nerve muscle functional unit -consists of the motor neuron and all muscle fibers (four to several hundred) it supplies -Smaller the fiber number, the greater the fine control

Of the following muscle types, which has only one nucleus, no sarcomeres, and few gap junctions? a) skeletal muscle b) visceral smooth muscle c) multiunit smooth muscle d) cardiac muscle

One of the important functions of skeletal muscle contraction is production of heat. a) True b) False

True/False: One of the important functions of skeletal muscle contraction is production of heat.

True

True/False: Peristalsis is characteristic of smooth muscle.

True

True/False: The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily.

True

True/False: The force of muscle contraction is controlled by multiple motor unit summation or recruitment.

True

True/False: The thin filaments (actin) contain a polypeptide subunit G actin that bears active sites for myosin attachment.

True

True/False: When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length.

True

Used to convert ADP to ATP by transfer of a high-energy phosphate group. A reserve high-energy compound.

creatine phosphate

When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length.

True

true/False: Smooth muscles relax when intracellular Ca2+ levels drop but may not cease contractions.

True

Which pathway for regenerating ATP provides the majority of the energy used for muscle activity during 30 minutes of light to moderate exercise?

aerobic respiration

Once a motor neuron has fired, all the muscle fibers in a muscle contract.

False

One of the important functions of skeletal muscle contraction is production of heat.

False

Oxygen debt refers to the oxygen required to make creatine phosphate.

False

Recruitment is an option in a single-unit smooth muscle cell.

False

T or F? ATP is required to cause the power stroke in the myosin head?

False

T or F? The longer a muscle is when it starts contracting, the more tension it can generate in the contraction

False

The longer a muscle is when it starts contracting, the more tension it can generate in the contraction.

False

The more slowly a skeletal muscle is stimulated, the greater its exerted force becomes.

False

True/False: A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate.

False

True/False: During isometric contraction, the energy used appears as movement.

False

True/False: Muscle contraction will always promote movement of body parts.

False

True/False: Once a motor neuron has fired, all the muscle fibers in a muscle contract.

False

Whereas skeletal muscle cells are electrically coupled, smooth muscle cells appear to be chemically coupled by gap junctions.

False

varicosities

(bulbous swellings) of nerve fibers store and release neurotransmitters into diffuse junctions

myofibrils

-Densely packed, rodlike elements: ~80% of cell volume -Mitochondria and other organelles are squeezed between them -features: Striations, Sarcomeres, Myofilaments, Molecular composition of myofilaments (Actin and myosin) -orderly arrangement of myofilaments within sarcomere

innervation of smooth muscle

No NMJ as in skeletal muscle: Autonomic nerve fibers innervate at diffuse junctions (somatic nerve fibers in skeletal)

motor nerve

-each muscle has at least 1 -contains axons of up to hundreds of motor neurons

Have very fast-acting myosin ATPases and depend upon anaerobic metabolism during contraction.

fast (oxidative or gylcolytic fatigable fibers)

What is the relationship between the number of motor neurons and the number of skeletal muscles innervated?

Typically, hundreds of skeletal fibers are innervated by a single motor neuron.

Addition of more myoglobin to a muscle fiber would have the largest effect on ________.

fast and slow oxidative fibers

List the characteristics of a White band

fast contracting unit; longer diameter, fewer mitochondria; fatique easily

Addition of more mitochondria to a muscle fiber will have the least effect on ________.

fast glycolytic fibers

Exhaustion of glycogen storage within a muscle fiber would have the biggest effect on ________.

fast glycolytic fibers

Cross Bridge Cycle: Step 2

the power stroke: ADP released and activated myosin head pivotes; Slides thin myofilament toward center of sarcomere

Generation of an Action Potential Across the Sarcolemma (2)

(generation and propagation of the action potential); [neuron send AP through axon] end plate potential ignites AP that spreads in all directions from neuromuscular junction across sarcolemma; this depolarization (end plate potential) spreads to adjacent membrane areas and opens voltage gated sodium channels; Na+ enters and reaches voltage threshold (+30), and an action potential is generated. AP is propegated along length of sarcolemma as depolarization wave spreads to adjacent areas of sarcolemma and opens voltage gated sodium channels there; again, Na+ difusses into cell

Generation of an Action Potential Across the Sarcolemma (1)

(local depolarization and generation of an end plate potential); Binding of ACh molecules to ACh receptors at neuromuscular junction opens (ligand) gated ion channels that allow Na+ and K+ to pass; More Na+ diffuses in then K+ diffuses out and interior of sarcolemma becomes less negative (depolarization [local electrical event called, end plate potential)

Generation of an Action Potential Across the Sarcolemma (3)

(repolarization); sarcolemma is restored to intitial polarized state; Na+ channels close and voltage-gated K+ channels open; K+ efflux rapidly restores the resting polarity; Fiber cannot be stimulated and is in a refractory period until repolarization is complete; Ionic conditions of the resting state are restored by the Na+-K+ pump

direct skeletal muscle attachment

-(fleshy) -epimysium fused to periosteum of bone or perichondrium of cartilage

rigor mortis

-3-4 hours after death, muscles begin to stiffen: Peak rigidity occurs about 12 hours postmortem -Intracellular calcium levels increase because ATP is no longer being synthesized, so calcium cannot be pumped back into SR -Results in myosin head staying bound to actin, causing constant state of contraction, stay contracted until muscle proteins break down

heat production during muscle activity

-40% of energy released in muscle activity useful as work -Remaining energy (60%) given off as heat

Polarized

-70 (resting plasma potential)

end plate potential (-90mV to -something)

-ACh binding opens chemically (ligand) gated ion channels -Simultaneous diffusion of Na+ (inward) and K+ (outward) -More Na+ diffuses in, so interior of sarcolemma becomes less negative> results in local depolarization

skeletal muscles

-Attached to bones and skin -muscle fibers are longest of all muscle and have striations (stripes) -Contract rapidly but tire easily; Powerful -Key words: skeletal, striated, and voluntary

role of Ca2+ in smooth muscle contraction

-Ca2+ binds to and activates calmodulin -Activated calmodulin activates myosin kinase -myosin kinase phosphorylates and activates myosin -Cross bridges interact with actin -When intracellular Ca2+ levels drop > relaxation

at higher intracellular Ca2+ concentration

-Ca2+ binds to troponin -Troponin changes shape and moves tropomyosin away from myosin-binding sites -Myosin heads bind to actin, causing sarcomere shortening and muscle contraction -When nervous stimulation ceases, Ca2+pumped back into SR and contraction ends

period of relaxation

-Ca2+ reentry into SR; tension declines to zero -3rd phase of muscle twitch

elastic filament

-Composed of protein titin -Holds thick filaments (myosin) in place; helps recoil after stretch; resists excessive stretching

muscle tone

-Constant, slightly contracted state of all muscles -due to spinal reflexes (Groups of motor units alternately activated in response to input from stretch receptors in muscles)

actin

-Contains the active sites to which myosin heads attach during contraction -regulatory proteins bound: troponin and tropomyosin

t tubules

-Continuations of sarcolemma (stick off of plasma membrane) -Tubules penetrate cell's interior at each A-I band junction between terminal cisterns (part of SR) -detect voltage change (change shape) and tell SR integral proteins to release Ca2+ -helps sarcomeres communicate

Direct phosphorylation of ADP by creatine phosphate

-CrP is located in muscle fibers and donates a phosphate to ADP to instantly form ATP -Creatine kinase phosphorylates it to power cell for 15 seconds

Cross Bridge Cycle: Step 3

cross bridge detachment: Link between mysoin head and actin weakens when another ATP ataches to myosin head; Myosin head detaches

sliding filament model of contraction

-During contraction, thin filaments slide past thick filaments: actin and myosin overlap more -Occurs when myosin heads bind to actin forming cross bridges -Cross bridges form and break several times, ratcheting thin filaments toward center of sarcomere

muscle fiber

-Each fiber is long and cylindrical, 10 to 100 μm in diameter; up to 30 cm long -multinucleated -Produced by the fusion of multiple embryonic cells -Modified structures: myofibrils, sarcoplasmic reticulum, and T tubules

myosin

-Each molecule has a rod-like tail and two globular heads made of polypeptides -During contraction, heads link thick and thin filaments together, forming cross bridges

skeletal muscle anatomy

-Each muscle served by one artery, one nerve, and one or more veins that enter/exit near central part and branch through connective tissue sheaths -1 nerve ending per fiber to control its activity

steps 3 and 4 of skeletal muscle contraction (EC coupling)

-Events that transmit AP along sarcolemma lead to sliding of myofilaments (contraction) -AP is propagated along sarcolemma and down into T tubules, where voltage-sensitive proteins in tubules stimulate Ca2+ release from SR -Ca2+ release = contraction

characteristics of muscle tissue

-Excitability(responsiveness): ability to receive and respond to stimuli -Contractility: ability to shorten forcibly when stimulated -Extensibility: ability to be stretched -Elasticity: ability to recoil to resting length

muscle tissue

-Nearly half of body's mass -Transforms chemical energy (ATP) to directed mechanical energy that exerts force -Skeletal, Cardiac, Smooth

step 1 of skeletal muscle contraction

-Nerve impulse arrives at axon terminal -voltage gated Ca2+ channels open and release Ca2+ into axon terminal -causes ACh to be released into synaptic cleft and bind to receptors on sarcolemma

graded muscle response

-Normal muscle contraction is relatively smooth, and strength varies with needs -Responses graded by changing frequency and changing strength of stimulation

muscle fatigue

-Physiological inability to contract despite continued stimulation -occurs when: Ionic imbalances (K+, Ca2+, Pi) interfere with EC coupling and Prolonged exercise may damage SR and interferes with Ca2+ regulation and release

Aerobic respiration

-Produces 95% of ATP during rest and light-to-moderate exercise -Fuels used include glucose from glycogen stored in muscle fiber, then bloodborne glucose, and free fatty acids (main fuel after 30 min of exercise) -32 ATP per glucose, hours of power time

nerve stimulus

-Skeletal muscles stimulated by somatic motor neurons, Axons (long, threadlike extensions of motor neurons) travel from central nervous system to skeletal muscle

3 types of muscle fibers

-Slow oxidative fibers; Fast oxidative fibers; Fast glycolytic fibers -most muscle fibers contain multiple types -All fibers in one motor unit same type

contraction of smooth muscle

-Slow, synchronized contractions -Cells electrically coupled by gap junctions -Some cells self-excitatory (depolarize without external stimuli); act as pacemakers for sheets of muscle

sarcomere

-Smallest contractile unit (functional unit) of muscle fiber (the region of a myofibril between two successive Z discs) -where contraction happens -multiple make up myofibrils

muscle fiber classification

-Speed of contraction: slow or fast fibers -metabolic pathways for ATP synthesis: Oxidative fibers (use aerobic pathways) Glycolytic fibers (use anaerobic glycolysis)

at low intracellular Ca2+ concentration

-Tropomyosin blocks active sites on actin -Myosin heads cannot attach to actin -Muscle fiber relaxed -Voltage-sensitive proteins in T tubules change shape, causing SR to release Ca2+ to cytosol

latent period

-events of excitation-contraction coupling; no muscle tension -1st phase of muscle twitch

period of contraction

cross bridge formation occurs

The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily.

true

sarcoplasm

-cytoplasm of muscle fiber -Glycosomes for glycogen storage -Myoglobin for O2 storage

A band

-dark regions, actin and myosin -H zone: lighter region in middle of dark A band (only myosin) -M line: line of protein (myomesin) that bisects H zone vertically (only myosin with accessory proteins)

Force of Muscle Contractions

-depends on number of cross bridges attached, which is affected by four factors

myasthenia gravis

-disease characterized by drooping upper eyelids, difficulty swallowing and talking, and generalized muscle weakness -Involves shortage of Ach receptors because person's ACh receptors are attacked by own antibodies (autoimmune disease)

depolarization (0 to +3)

-generation and propagation of an action potential (AP) -If end plate potential causes enough change in membrane voltage to reach critical level called threshold, voltage-gated Na+ channels in membrane will open (closed K+ channel) -Large influx of Na+ through channels into cell triggers AP that is unstoppable and will lead to muscle fiber contraction -AP spreads across sarcolemma

muscular dystrophy

-group of inherited muscle-destroying diseases -Muscles enlarge as a result of fat and connective tissue deposits, but then atrophy and degenerate -Duchenne muscular dystrophy (DMD) is the most common and severe type

Anaerobic pathway (glycolysis > lactic acid)

-in high intensity exercise, Bulging muscles compress blood vessels, impairing oxygen delivery -lactic acid is used as fuel by liver, kidneys, and heart and is converted back into pyruvic acid or glucose by liver -2 ATP, powers cell for 30-40 seconds

sarcoplasmic reticulum

-is a network of smooth endoplasmic reticulum tubules surrounding each myofibril -Contains terminal cisterns that regulates intracellular Ca2+ levels -Stores and releases Ca2+

I bands

-lighter regions: only has actin -Z disc (line): coin-shaped sheet of proteins on midline of light I band

connective tissue sheaths of skeletal muscle

-membrane -Support cells; reinforce whole muscle -external to internal: Epimysium, Perimysium, endomysium

Duchenne muscular dystrophy (DMD)

-most common and severe type of muscular dystrophy -Caused by defective gene for dystrophin -Inherited, sex-linked trait, carried by females and expressed in males (1/3600)

degree of muscle stretch

-muscle fibers with sarcomeres that are 80-120% their normal resting length generate more force -If sarcomere is less than 80% resting length, filaments overlap too much, and force decreases -If sarcomere is greater than 120% of resting length, filaments do not overlap enough so force decreases

The force of muscle contraction is controlled by multiple motor unit summation or recruitment.

true

a) Z disc -(from the German "Zwischenscheibe", the band in between the I bands) appears as a series of dark lines.

A sarcomere is defined as the segment between two neighboring Z-lines (or Z-discs, or Z bodies). In electron micrographs of cross-striated muscle, the ___. a) Z disc b) H zone c) I band d) A band e) M line

isometric contraction

-no muscle shortening; muscle tension increases but does not exceed load -tension increases to the muscle's peak tension-developing capability

ACh binding to receptors

-opens Na+ K+ pump -3 Na+ in and 2 K+ out which makes inside of cell go from negative to positive

muscle tension

-produced by contraction -force exerted on load or object to be moved

repolarization (-10mV ish to -90mV)

-restoration of resting conditions -Na+ voltage-gated channels close, and voltage-gated K+ channels open -K+ efflux out of cell rapidly brings cell back to initial resting membrane voltage -restored with Na+ K+ pump

smooth muscle does not contain

-sarcomeres, myofibrils, or T tubules -SR is less developed than in skeletal muscle

muscle twitch

-simplest contraction resulting from a muscle fiber's response to a single action potential from motor neuron -Muscle fiber contracts quickly, then relaxes -can be observed and recorded as a myogram

striations

-stripes formed from repeating series of dark and light bands along length of each myofibril -A band (dark) and I band (light)

maximal stimulus

-strongest stimulus that increases contractile force -all motor units are stimulated and cannot do anymore

contraction

-the activation of cross bridges to generate force -Shortening occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening -Contraction ends when cross bridges become inactive

Muscle tone is ________.

A state of sustained partial contraction.

Wave (temporal) summation

-type of graded muscle response that results if two stimuli are received by a muscle in rapid succession -Produces smooth, continuous contractions that add up (summation)

neuromuscular junction

-when an axon ends at a single muscle fiber -Situated midway along length of muscle fiber -includes axon terminals, synaptic cleft (gel space that separates axon terminal and muscle fiber), junctional folds

Explain how a slight but smooth contraction differs from a vigorous contraction of the same muscle; use the concepts of multiple motor unit summation

...

Thick and thin myofilaments have different compositions.

...

What is the importance of acetylcholinesterase in muscle contraction?

...

The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure? 1 and 7 3 and 5 1 and 3 2 and 6

1 and 7

The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure? (see figure 2) 3 and 5 2 and 6 1 and 3 1 and 7

1 and 7

During muscle contraction, ATP is provided by A) A coupled reaction of creatine phosphate with ADP B) Aerobic respiration of glucose C) Anaerobic glycolysis 1) Which provides ATP fastest? 2) Which does (do) not require that oxygen be available? 3) Which provides the highest yield of ATP per glucose molecule? 4) Which results in the formation of lactic acid? 5) Which has carbon dioxide and water products? 6) Which is most important in endurance sports?

1) A- A coupled reaction of creatine phosphate with ADP 2) A/C- A coupled reaction of creatine phosphate with ADP, Anaerobic glycolysis 3) B- Aerobic respiration of glucose 4) C- Anaerobic glycolysis 5) B- Aerobic respiration of glucose 6) B- Aerobic respiration of glucose

Thick and thin myofilaments have different compositions. For each descriptive phrase, indicate whether the filament is A- thick or B- thin. 1) Contains actin 2) ATPases 3) Attaches to the Z disc 4) Contains myosin 5) Contains troponin 6) Does not lie in the I band

1) B-thin 2) A-thick 3) B-thin 4) A-thick 5) B-thin 6) A-thick

What are three reasons for muscle fatigue?

1) Build up too much lactic acid 2) not enough calcium (calcium problems) 3)Not enough ATP available

what are the functions of a muscle tissue?

1) produces movement 2)maintains posture 3) stabilizes joints 4) generates head

List the Twitch steps in order

1)Latent Period 2) Period of Contraction 3) period of relaxation 4) refractory period

What are the uses for ATP during muscle contraction?

1)make cross bridges 2)Break cross bridges 3)Energize powerstroke of myosin 4)Pump calcium ions back into storage (Storage being Sacroplasmic Reticulum)

Sequence of events during Excitation - Contraction Coupling

1. Ap propagates along sarcolemma 2. AP travels down T tubules to triads 3. Voltage sensitive proteins open Ca 2+ channels 4.Sarcoplasmic reticulum releases Ca 2+ 5. Ca2+ levels in sarcoplasm increase Recall from the video that a single motor neuron can conduct action potentials to several skeletal muscle fibers within a muscle. Excitation-contraction coupling converts these action potentials in a muscle fiber to a contraction. As muscle fibers contract, the entire muscle shortens and pulls the tendons on either end of the muscle, producing muscle tension.

Which provides ATP fastest?

A) a coupled reaction of creatine phosphate with ADP

Which does (do) not require that oxygen be available?

A) a coupled reaction of creatine phosphate with ADP) & C) Aneaerobic glycolysis

sequence of events at the neuromuscular junction

1. Ca 2+ enters the axon terminal 2. synaptic vesicles release ACh 3. ACh binds to ACh receptors 4. Ligand gated cation channels open 5. Na+ enters and K+ exists 6. Membrane potential is less negative The neuromuscular junction is a chemical synapse. An electrical signal (known as an action potential) from the motor neuron is converted into a chemical signal (ACh release). The skeletal muscle fiber responds to the chemical signal (ACh) by depolarizing and initiating an action potential. This action potential is propagated along the sarcolemma of the muscle fiber, which triggers sliding of the myofilaments for muscle contraction.

During muscle contraction, ATP is provided by

A) a coupled reaction of creatine phosphate with ADP, B) aerobic desperation of glucose, and C) anaerobic glycolysis

If the cell could no longer produce ATP, what would be the effect on the sarcoplasmic reticulum? >It would be unable to concentrate Ca+ in the sarcoplasmic reticulum. >Ca+ would leak out of the cell. >The muscle would not contract. >Ca+ would build up in the sarcoplasmic reticulum.

>It would be unable to concentrate Ca+ in the sarcoplasmic reticulum. To concentrate Ca+ in the sarcoplasmic reticulum, active transport must occur. With no ATP, there would be no active transport.

What is the functional unit of a skeletal muscle called? A) a sarcomere B) a myofilament C) a myofibril D) the sarcoplasmic reticulum

A) a sarcomere

muscle functions

1.Produce movement: responsible for all locomotion and manipulation 2.Maintain posture and body position 3.Stabilize joints 4.Generate heat as they contract -other: Protect organs, form valves, control pupil size, cause "goosebumps"

One action potential in a motor neuron causes the full reaction in skeletal muscle, which is called a twitch. One twitch can generate max tension in a muscle. Are these statements true or false?

1st = true 2nd = false

How many motor neurons are in the Autonomic Nervous system?

2 Motor Neurons

What composes the Triad?

2 Terminal Cisterns; Transverse Tubule

Between which two points would there be substantial amounts of both the proteins actin and myosin? 2 and 3 1 and 2 3 and 5 None of the listed responses is correct.

2 and 3

The region between which two points corresponds to the entire A (dark) band? (see figure 2) 1 and 2 3 and 5 2 and 3 2 and 6

2 and 6

The region between which two points corresponds to the entire A band? 2 and 6 3 and 5 2 and 3 1 and 2

2 and 6

Depolarized

30 (for action potential to occur)

The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure? (img 1) >3 and 5 >1 and 3 >1 and 7 >2 and 6

>1 and 7. The distance between points 1 and 7 spans a sarcomere, the smallest contractile unit of a muscle fiber.

The region between which two points corresponds to the entire A (dark) band? (img 1) Relationship between fibers composing a sarcomere. >1 and 2 >2 and 3 >3 and 5 >2 and 6

>2 and 6 The A band, also know as the dark band, is occupied by the entire length of thick myofilaments.

The molecular interaction described as a cross bridge involves the binding of which two proteins? (img 5) >A and C >B and D >A and D >A and B

>A and C. Cross bridges between thin and thick myofilaments are formed by the specific interaction between actin (A) and myosin head groups (C).

Which step precedes all of the other listed steps? >The sarcoplasmic reticulum is activated. >An action potential starts on the sarcolemma. >Na+ rushes into the cell. >ACh is released by the motor neuron.

>ACh is released by the motor neuron. The first step toward generating a skeletal muscle contraction is nervous stimulation of the muscle fiber in order to generate an action potential. The site of muscle stimulation, where the nerve ending communicates with the muscle fiber, is called the neuromuscular junction.

Which of the following interactions must occur first so that the others can take place? (Refer to img 5) Interaction between thick and thin filaments during muscle contraction. >B binds to troponin. >D is shifted from actin's binding sites. >C binds to actin. >C releases ADP and P.

>B binds to troponin. Binding of calcium (B) to troponin removes the blocking action of tropomyosin along the thin myofilament. This allows myosin to bind to actin and form the cross bridge illustrated in this figure.

Which of the following corresponds to a single fascicle? (img 4) >A >B >C >D

>B. A fascicle is an organized group of muscle fibers (cells) bounded by a perimysium.

Which of the structures is surrounded by the connective tissue sheath known as the perimysium? (img 4) A B C D

>B. The structure at B is covered by the perimysium. Remember that the word root peri means "around," as in "perimeter."

Which statement accurately describes the event indicated by B? (img 2) >The binding of acetylcholine directly causes the formation of a wave of depolarization. >Diffusion of acetylcholine into the muscle fiber triggers the opening of an ion channel. >Binding of acetylcholine to a receptor triggers the opening of an ion channel. >Diffusion of Ca2+ into the muscle fiber triggers the diffusion of acetylcholine out of the muscle fiber.

>Binding of acetylcholine to a receptor triggers the opening of an ion channel. Binding of acetylcholine to its receptor opens chemically (ligand) gated ion channels that allow Na+ and K+ to diffuse across the sarcolemma.

Which structure in the figure corresponds to a single skeletal muscle cell? (img 4) >A >B >C >D

>C. Note that a skeletal muscle cell is commonly termed a muscle fiber.

Which protein functions as a motor protein that applies the power stroke during muscle contraction? (img 5) >A >B >C >D

>C. The myosin head groups (C) hydrolyze ATP to power molecular movement along the actin subunits of the thin myofilaments.

Based on what you know of the relationship between the thick and the thin filaments, what would happen if a disorder existed that caused a person to produce no tropomyosin? >The muscle tissues would never be able to relax. >The muscle would be weaker than normal. >Actin will spontaneously fall apart. >The muscle would never contract.

>The muscle tissues would never be able to relax. The tropomyosin covers the myosin binding site on actin. Without tropomyosin, the myosin would constantly have access to those binding sites.

In the muscles of the limbs, the origin is usually the immobile muscle attachment. >True >False

>True. In the muscles of the limbs, the insertion is pulled toward the immobile origin.

Which protein is indicated by the letter A? (img 5) >actin >troponin >myosin >keratin

>actin. Actin is the chief component of the thin myofilaments.

What event directly triggers the release of neurotransmitter shown in A? (img 2) Summary of events at a neuromuscular synapse. >diffusion of Na+ into the axon terminal >diffusion of Na+ out of the axon terminal >diffusion of Ca2+ into the axon terminal >diffusion of K+ into the axon terminal

>diffusion of Ca2+ into the axon terminal. A nerve impulse arrives at the axon terminal triggering the opening of Ca2+ channels, which allows for the diffusion of Ca2+ into the terminal. This in turn leads directly to the release of neurotransmitters by exocytosis.

The sliding filament model of contraction states that __________. >during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments no longer overlap >during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree >during contraction, the thin myofilaments slide past the thick myofilaments so that calcium ions can be released from the sarcoplasmic reticulum >during contraction, the thin myofilaments slide past T tubules so that the Z discs are overlapping

>during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree. The sliding filament model of contraction states that during contraction, the thin myofilaments slide past the thick myofilaments so that actin and myosin myofilaments overlap to a greater degree. In a relaxed muscle fiber, the thick and thin myofilaments overlap only at the ends of the A band.

Muscle tissue can be stimulated by the nervous system. This is because of the membrane potential in the muscle cell. Cells with a membrane potential have what property? >excitability >extensibility >elasticity >contractility

>excitability. Excitability, also termed responsiveness, is the ability to receive and respond to a stimulus. For example, skeletal muscle contracts in response to receiving chemical stimulation from the central nervous system.

What cellular event is indicated by A? >endocytosis >facilitated diffusion >active transport >exocytosis

>exocytosis. Neurotransmitters stored in synaptic vesicles are released into the synaptic cleft by exocytosis.

Which term best identifies a muscle cell? >sarcomere >muscle fascicle >myofibril >muscle fiber

>muscle fiber. Skeletal muscle cells fuse during development to form the mature, multinucleated muscle fibers.

Which term best identifies a muscle cell? >sarcomere >myofibril >muscle fiber >muscle fascicle

>muscle fiber. Skeletal muscle cells fuse during development to form the mature, multinucleated muscle fibers.

Which protein is indicated by the letter E? (img 5) >tropomyosin >troponin >actin >myosin

>myosin. Myosin tail groups form the extended regions of the thick myofilament.

What is the function of the filaments found in ranges 1-2 and 6-7 but no other ranges? (Refer to img 1) Relationship between fibers composing a sarcomere. >neurological sensing of the muscle's tension >a connection between the myosin fibers and a calcium source >adding strength to contraction >protection from overstretching

>protection from overstretching. Elastic (titin) filaments help to protect the muscle from overstretching and also aid in returning it to normal length.

Excitation-contraction coupling includes all EXCEPT which of the following events? >release of acetylcholine from axon terminals at the neuromuscular junction >binding of calcium ions to troponin, which removes the blocking action of tropomyosin >propagation of an action potential along the sarcolemma and down T tubules >release of calcium ions from the terminal cisterns

>release of acetylcholine from axon terminals at the neuromuscular junction. Release of acetylcholine from axon terminals at the neuromuscular junction is an event that precedes excitation-contraction coupling, which begins with excitation of the T-tubules.

The __________ shorten(s) during muscle contraction >Z lines >thick filament >actin >sarcomere

>sarcomere. As actin slides over myosin, the z lines are pulled closer together, shortening the sarcomere.

Which of the following is NOT a normal function of muscle tissue? >secreting hormones >generating heat >stabilizing joints >maintaining posture >producing movement

>secreting hormones. Secreting hormones is a function of the endocrine system.

Which of the following are correctly paired? >smooth muscle; striated >skeletal muscle; voluntary control >cardiac muscle; nonstriated >cardiac muscle; voluntary control

>skeletal muscle; voluntary control.

Which type of muscle requires voluntary nervous stimulation for activation? >skeletal >smooth >cardiac >visceral

>skeletal. In order to contract, skeletal muscle fibers must be voluntarily stimulated by the nervous system. The site of muscle stimulation, where the nerve fiber communicates with the muscle fiber, is called the neuromuscular junction.

The connective tissue that covers structure A is continuous with which of the following? >ligament >synovial membrane >endomysium >tendon

>tendon. The dense connective tissue at A is continuous with the tendon that connects the muscle to a bone or, in some cases, to another muscle or to the skin.

Describe the structure of a sarcomere and indicate the relationship of the sacromere to myofilaments.

A sarcomere is a segment of a myofibril containing thick and thin filaments. Sarcomere is the contractile unit, composed of myofilaments.

A toxin released by certain bacteria can block the release of neurotransmitters into a neuromuscular synapse. What would result from such a block? >The muscle would become permanently contracted. >The muscle would remain fixed at the length it was when the toxin contacted it. >the loss of ability to contract the muscle

>the loss of ability to contract the muscle. Without acetylcholine, the muscle would not be able to contract or even maintain tone.

Which of the following regions best identifies where myosin would have maximum cross-bridge access to actin? (img 1) >the region between 1 and 2 >4 >the region between 3 and 5 >the region between 2 and 3

>the region between 2 and 3. Actin and myosin are components of thin and thick filaments, respectively. The region between points 2 and 3 includes the area of overlap between thin and thick filaments.

The contractile, or functional, unit of a muscle fiber is __________. >the myofilament >troponin >the sarcomere >the elastic filament

>the sarcomere. The sarcomere is the contractile unit of a muscle fiber and the smallest functional unit of muscle. A sarcomere is the region of a myofibril between two successive Z discs; it primarily consists of thin and thick myofilaments.

Which organelle can chemically regulate the shortening of the muscle? >the sarcolemma >the sarcoplasmic reticulum >the myofibril >glycosome

>the sarcoplasmic reticulum

An enzyme known as acetylcholinesterase is present in the synaptic cleft. What is its role? >to facilitated transport of acetylcholine across the cleft >to pump Ca2+ back out of the axon terminal >to facilitate the entrance of acetylcholine into the muscle cell >to break down acetylcholine

>to break down acetylcholine. Acetylcholinesterase breaks acetylcholine apart, terminating the synaptic transmission. Choline can be taken back into the axon terminal and reused.

The interaction between which protein and ion initiates contraction of skeletal muscle? >tropomyosin; calcium ions >troponin; calcium ions >myosin; sodium ions >troponin; sodium ions

>troponin; calcium ions. When calcium ions bind to troponin, troponin changes shape and moves tropomyosin away from its inhibitory position. As a result, the energized myosin heads can bind to the actin molecules and begin the cross bridge cycle, which shortens the muscle fiber.

Which band is myosin and actin?

A Band

What structure is the functional unit of contraction in a skeletal muscle fiber? The sarcomere The junctional folds of the sarcolemma The triad The cross bridge

A THE SARCOMERE A sarcomere is a regular arrangement of thin and thick myofilaments that extends from one Z disc to the next. A myofibril consists of a series of sarcomeres.

The molecular interaction described as a cross bridge involves the binding of which two proteins? (see figure 4) A and B B and D A and D A and C

A and C

Both actin and myosin are found in the

A band

Both actin and myosin are found in the ________.

A band

The myosin filaments are located in the

A band

The myosin filaments are located in the ________.

A band

4. Both actin and myosin are found in the

A band.

5. The myosin filaments are located in the

A band.

What most directly causes synaptic vesicles to release acetylcholine into the synaptic cleft? A calcium entering the axon terminal B an action potential arriving at the axon terminal C sodium entering the muscle fiber D depolarization of the sarcolemma

A calcium entering the axon terminal Calcium entry causes synaptic vesicles to release acetylcholine into the synaptic cleft. Each synaptic vesicle contains thousands of acetylcholine molecules.

A) Slow (oxidative), fatigue-resistant fibers

A relatively high percentage are found in successful marathon runners. A) Slow (oxidative), fatigue-resistant fibers B) Fast (oxidative or glycolytic), fatigable fibers

What is the functional unit of a skeletal muscle called?

A sarcomere

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur? Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma). Binding causes voltage-gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma). Binding causes chemically gated potassium channels to open in the motor end plate (junctional folds of the sarcolemma). Binding causes potassium voltage-gated channels to open in the motor end plate (junctional folds of the sarcolemma).

A) Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma). Yes, sodium enters the cell and causes depolarization. A small amount of potassium also leaves the motor end plate (junctional folds of the sarcolemma).

How is acetylcholine (ACh) removed from the synaptic cleft? acetylcholinesterase (AChE; an enzyme) a reuptake pump on the axon terminal simple diffusion away from the synaptic cleft All of the above.

A) acetylcholinesterase (AChE; an enzyme) Acetylcholinesterase breaks down acetylcholine in the synaptic cleft.

The giant protein titin maintains the organization of the ________ assisting in muscle stretching. A) A band B) I band C) Z disc D) M line

A) A band

A myosin head binds to which molecule to form a cross bridge? actin troponin tropomyosin

A) ACTIN Yes, the binding of ATP causes the myosin head to disconnect from actin

The neurotransmitter released by somatic motor neurons is... A) Acetylcholine B) Acetylcholinesterase C) Norepimephrine

A) Acetylcholine

Excitation-contraction coupling requires which of the following substances? A) Ca2+ and ATP B) Ca2+ only C) ATP only D) ATP and glucose

A) Ca2+ and ATP

Which of the following is true about smooth muscle contraction? A) Certain smooth muscle cells can actually divide to increase their numbers. B) Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements. C) Smooth muscle cannot stretch as much as skeletal muscle. D) Smooth muscle has well-developed T tubules at the site of invagination.

A) Certain smooth muscle cells can actually divide to increase their numbers.

Which of the following statements is most accurate? A) Muscle tension remains relatively constant during isotonic contraction. B) T tubules may be sliding during isotonic contraction. C) The I band lengthens during isotonic contraction. D) Myofilaments slide during isometric contractions.

A) Muscle tension remains relatively constant during isotonic contraction.

The sites where the motor neuron impulse is transmitted from the nerve endings to the skeletal muscle cell membranes are the... A) Neuromuscular Junctions B) Sarcomeres C) Myofilaments D) Z Discs

A) Neuromuscular Junctions

Characteristics of isometric contractions include all but... A) Shortening B) Increased muscle tension throughout the contraction phase C) Absence of shortening D) Used in resistance training

A) Shortening

Which type of muscle requires voluntary nervous stimulation for activation? A) skeletal B) cardiac C) smooth D) visceral

A) Skeletal In order to contract, skeletal muscle fibers must be voluntarily stimulated by the nervous system. The site of muscle stimulation, where the nerve fiber communicates with the muscle fiber, is called the neuromuscular junction.

How does the myosin head obtain the energy required for activation? The energy comes from the hydrolysis of ATP. The energy comes from oxidative phophorylation. The energy comes from the hydrolysis of GTP. The energy comes from the direct phosphorylation of ADP by creatine phosphate.

A) The energy comes from the hydrolysis of ATP. Yes! Myosin is a large, complex protein with a binding site for actin. It also contains an ATPase. The energy released during the hydrolysis of ATP activates the myosin head.

Contraction elicited by a single brief stimulus is called... A) Twitch B) Wave summation C) Multiple motor unit summation D) Fused tetanus

A) Twitch

The sliding filament model of contraction involves ________. A) actin and myosin sliding past each other and partially overlapping B) the shortening of thick filaments so that thin filaments slide past C) actin and myosin shortening but not sliding past each other D) the Z discs sliding over the myofilaments

A) actin and myosin sliding past each other and partially overlapping

In an isotonic contraction, the muscle ________. A) changes in length and moves the "load" B) does not change in length but increases tension C) never converts pyruvate to lactate D) rapidly resynthesizes creatine phosphate and ATP

A) changes in length and moves the "load"

What part of the sarcolemma contains acetylcholine receptors? A) motor end plate B) end of the muscle fiber C) part adjacent to another muscle cell D) any part of the sarcolemma

A) motor end plate

Which of the following is the correct sequence of events for muscle contractions? A) motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments B) neurotransmitter release, muscle cell action potential, motor neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke C) muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments D) neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke

A) motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments

What structure in skeletal muscle cells functions in calcium storage? A) sarcoplasmic reticulum B) mitochondria C) intermediate filament network D) myofibrillar network

A) sarcoplasmic reticulum

Muscle tissue has all of the following properties except ________. A) secretion B) contractility C) extensibility D) excitability

A) secretion

which of the following are correctly paired? A) skeletal muscle; voluntary control B) cardiac muscle; voluntary control C) smooth muscle; striated D) cardiac muscle; nonstriated

A) skeletal muscle; voluntary control

Which of the following are composed of myosin? A) thick filaments B) thin filaments C) all myofilaments D) Z discs

A) thick filaments

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell? arrival of an action potential ATP calcium ion pump troponin

A)arrival of an action potential an action potential in the T tubule causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum.

Termination of Neural Transmission Which of the following is/are mechanism(s) to end neural transmission at the neuromuscular junction? Select all the correct answers. ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE). ACh diffuses away from the synaptic cleft. ACh is taken up by the axon terminal via endocytosis. ACh binds to ACh receptors.

ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE). ACh diffuses away from the synaptic cleft. The chemical signal (ACh) at the neuromuscular junction is very short! Soon after ACh is released from the axon terminal, it is rapidly degraded by AChE or diffuses out of the synaptic cleft. These two mechanisms ensure that just enough ACh binds to its receptor to initiate an action potential and that the muscle fiber's response is quickly terminated.

acetylcholinesterase

ACh is quickly broken down by this enzyme which stops contractions

Which step precedes all of the other listed steps?

ACh is released by the motor neuron

Which step precedes all of the other listed steps? Which step precedes all of the other listed steps? An action potential starts on the sarcolemma. Na+ rushes into the cell. The sarcoplasmic reticulum is activated. ACh is released by the motor neuron.

ACh is released by the motor neuron.

Direct Phosphorylation

ATP producing way; Metabolic Pathway; chemical reaction where CP (creatine phosphate) and ADP are used. Phosphate from CP is taken and put into ADP and turns to ATP; 1 to 1 ration; energy last for less then 10 seconds; does not require Oxygen;first stage body goes to to make energy; occurs in cytoplasm of cell

A) Slow (oxidative), fatigue-resistant fibers

Abundant in muscles used to maintain posture. A) Slow (oxidative), fatigue-resistant fibers B) Fast (oxidative or glycolytic), fatigable fibers

A neurotransmitter released at motor end plates by the axon terminals.

Acetylcholine

What is released by the telodenria of a motor neuron?

Acetylcholine

In a muscle fiber contraction what neurotransmitter is released at the terminal end of a motor neuron?

Acetylcholine (Ach)

During muscle contraction, myosin cross bridges attach to which active sites?

Actin filaments

During muscle contraction, myosin cross bridges attach to which active sites? myosin filaments thick filaments actin filaments Zdiscs

Actin filaments

How/when does the myosin head cock back to store energy for the next cycle?

After the myosin head detaches, energy from ATP hydrolysis is used to re-cock the myosin head.

________ are the muscles primarily responsible for producing a particular movement

Agonists

What do the genioglossus, hyoglossus, and styloglossus muscles have in common?

All act on the tongue.

Cross Bridge Cycle: Step 1

cross bridge formation:Activated myosin head binds to actin forming a cross bridge; Inorganic phospahte released; Bond between myosin and actin becomes stronger

Although all the anatomical parts of muscle work together to give it it's characteristics, which of the following proteins listed below would be most associated with the characteristics of contractility? a) potassium (K+) leak channels b) voltage gated sodium channels c) elastic (titin) filaments d) thick (myosin) filaments

Although all the anatomical parts of muscle work together to give it it's characteristics, which of the following proteins listed below would be most associated with the characteristics of excitability? a) the Na+-K+ pump b) acetylcholine receptors in the motor end plate c) elastic (titin) filaments d) actin of thin filaments

Although all the anatomical parts of muscle work together to give it it's characteristics, which of the following proteins listed below would be most associated with the characteristics of extensibility? a) elastic (titin) filaments b) acetylcholine receptors in the motor end plate c) thick (myosin) filaments d) potassium (K+) leak channels

e) Perimysium -A sheath of connective tissue that groups individual muscle fibers (anywhere between 10 to 100 or more) into bundles of fascicles.

Around the fasicles. Connective tissue surrounding muscle fiber bundles. a) Epimysium b) Endomysium c) Muscle Fiber d) Fascicle e) Perimysium

Role of Calcium (Ca2+) in Contraction

At low intracellular Ca2+ concentration: (Tropomyosin blocks the active sites on actin) (Myosin heads cannot attach to actin) (Muscle fiber relaxes) At higher intracellular Ca2+ concentrations: [Ca2+ binds to troponin ] [Troponin changes shape and moves tropomyosin away from active sites] [Events of the cross bridge cycle occur] [When nervous stimulation ceases, Ca2+ is pumped back into the SR and contraction ends]

skeletal muscle attachment

Attach in at least two places -Insertion- movable bone -Origin- immovable (less movable) bone -When muscles contract the insertion moves toward the origin

In which phase of the muscle twitch shown in the figure would the maximum amount of ATP be consumed by myosin head groups? (see figure 6)

Which of the following corresponds to a single fascicle? (see figure 1)

Which of the structures is surrounded by the connective tissue sheath known as the perimysium? (see figure 1)

Which structure corresponds to a single fascicle? A B C D

Which of the following interactions must occur first so that the others can take place? (see figure 4) C releases ADP and P. D is shifted from actin's binding sites. C binds to actin. B binds to troponin.

B binds to troponin

Acetylcholine receptors are best characterized as what type of channel? A voltage-gated Na+-K+ channels B chemically gated Na+-K+ channels C voltage-gated Ca2+ channels D chemically gated Ca2+ channels

B chemically gated Na+-K+ channels Chemically gated Na+-K+ channels allow the diffusion of Na+ into the muscle fiber and K+ out of the muscle fiber

The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure? A) 1 and 3 B) 1 and 7 C) 2 and 6 D) 3 and 5

B) 1 and 7 The distance between points 1 and 7 spans a sarcomere, the smallest contractile unit of a muscle fiber.

A fascicle is a... A) Muscle B) Bundle of muscle fibers enclosed by a connective sheath C) Bundle of myofibrils D) Group of myofilaments

B) Bundle of muscle fibers enclosed by a connective sheath

What is the role of tropomyosin in skeletal muscles? A) Tropomyosin is the name of a contracting unit. B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules. C) Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules. D) Tropomyosin is the receptor for the motor neuron neurotransmitter.

B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated? A) A skeletal muscle fiber is innervated by multiple motor neurons. B) Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. C) Motor neurons always innervate thousands of skeletal muscle fibers. D) A motor neuron typically innervates only one skeletal muscle fiber.

B) Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. There are many more skeletal muscle fibers than there are motor neurons. The ratio of neurons to fibers varies from approximately one to ten to approximately one to thousands.

The smooth muscle type found in the walls of digestive and urinary system organs and that exhibits gap junctions and pacemaker cells is... A) Multi unit B) Unitary

B) Unitary

Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers? A) a sprint by an Olympic runner B) a long, relaxing swim C) playing baseball or basketball D) mountain climbing

B) a long, relaxing swim

Most skeletal muscles contain ________. A) muscle fibers of the same type B) a mixture of fiber types C) a predominance of slow oxidative fibers D) a predominance of fast oxidative fibers

B) a mixture of fiber types

The term aponeurosis refers to ________. A) the bands of myofibrils B) a sheetlike indirect attachment to a skeletal element C) the rough endoplasmic reticulum D) the tropomyosin-troponin complex

B) a sheetlike indirect attachment to a skeletal element

During muscle contraction, myosin cross bridges attach to which active sites? A) myosin filaments B) actin filaments C) Z discs D) thick filaments

B) actin filaments

Which has carbon dioxide and water products?

B) aerobic desperation of glucose

Which is most important in endurance sports?

B) aerobic desperation of glucose

Which provides the highest yield of ATP per glucose molecule?

B) aerobic desperation of glucose

Which of the following surrounds the individual muscle cell? A) perimysium B) endomysium C) epimysium D) fascicle

B) endomysium

What is the functional role of the T tubules? A) stabilize the G and F actin B) enhance cellular communication during muscle contraction C) hold cross bridges in place in a resting muscle D) synthesize ATP to provide energy for muscle contraction

B) enhance cellular communication during muscle contraction

An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________. A) the citric acid cycle B) glycolysis C) hydrolysis D) the electron transport chain

B) glycolysis

Fatigued muscle cells that recover rapidly are the products of ________. A) intense exercise of long duration B) intense exercise of short duration C) slow exercise of long duration D) slow exercise of short duration

B) intense exercise of short duration

Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are ________. A) single-unit muscles B) multiunit muscles C) red muscles D) white muscles

B) multiunit muscles

Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions? A) visceral smooth muscle B) multiunit smooth muscle C) cardiac muscle D) skeletal muscle

B) multiunit smooth muscle

Cardiac muscle has a limited regenerative capacity. a) True b) False

What does oxygen deficit represent? A) amount of energy needed for exertion B) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used C) the amount of oxygen taken into the body prior to the exertion D) the amount of oxygen taken into the body immediately after the exertion

B) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used

Smooth muscle is characterized by all of the following except ________. A) it appears to lack troponin B) there are more thick filaments than thin filaments C) there are no sarcomeres D) there are noncontractile intermediate filaments that attach to dense bodies within the cell

B) there are more thick filaments than thin filaments

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? Calcium bound to troponin A myosin head bound to actin Troponin bound to tropomyosin ATP bound to a myosin head

B)A myosin head bound to actin As soon as the activated myosin head forms a cross bridge with actin, the power stroke begins.

Which statement accurately describes the event indicated by B? (see figure 3) The binding of acetylcholine directly causes the formation of a wave of depolarization. Diffusion of acetylcholine into the muscle fiber triggers the opening of an ion channel. Binding of acetylcholine to a receptor triggers the opening of an ion channel. Diffusion of Ca2+ into the muscle fiber triggers the diffusion of acetylcholine out of the muscle fiber.

Binding of acetylcholine to a receptor triggers the opening of an ion channel.

d) Fascicle -A bundle of skeletal muscle fibers surrounded by perimysium, a type of connecive tissue.

Bundles. Bundles of muscle cells surrounded by a perimysium. a) Epimysium b) Endomysium c) Muscle Fiber d) Fascicle e) Perimysium

In the figure above, which structure corresponds to a single skeletal muscle cell? A, B, C, D?

In which phase in the figure would the net movement of Ca2+ into the sarcoplasmic reticulum (SR) be greatest? (see figure 6)

Which protein functions as a motor protein that applies the power stroke during muscle contraction? (see figure 4)

Which structure in the figure corresponds to a single skeletal muscle cell? (see figure 1)

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction? A) Action potentials propagate into the interior of the skeletal muscle fiber. B) Voltage-sensitive proteins change shape. C) Calcium release from the sarcoplasmic reticulum initiates the contraction. D) Sodium release from the sarcoplasmic reticulum initiates the contraction.

C) Calcium release from the sarcoplasmic reticulum initiates the contraction. Yes! Sarcoplasmic reticulum is the specific name given to the smooth endoplasmic reticulum in muscle cells. It is especially abundant and convoluted in skeletal muscle cells. It functions in the storage, release, and reuptake of calcium ions.

Which of the following statements is false or incorrect? A) Cardiac muscle contracts when stimulated by its own autorhythmic muscle cells. B) Under normal resting conditions, cardiac muscle tissue contracts and relaxes about 75 times per minute. C) Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP. D) Cardiac muscle fibers can use lactic acid to make ATP.

C) Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP.

The connecting tissue covering that encloses the sarcolemma of the individual muscle fiber is called the... A) Epimysium B) Perimysium C) Endomysium D) Periosteum

C) Endomysium

Muscle tissue can be stimulated by the nervous system. This is because of the membrane potential in the muscle cell. Cells with a membrane potential have what property? A) elasticity B) contractility C) excitability D) extensibility

C) Excitability Excitability, also termed responsiveness, is the ability to receive and respond to a stimulus. For example, skeletal muscle contracts in response to receiving chemical stimulation from the central nervous system.

Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process? A) Excitation refers to the release of calcium ions from the sarcoplasmic reticulum. B) Excitation refers to the shape change that occurs in voltage-sensitive proteins in the sarcolemma. C) Excitation, in this case, refers to the propagation of action potentials along the sarcolemma. D) Excitation refers to the propagation of action potentials along the axon of a motor neuron.

C) Excitation, in this case, refers to the propagation of action potentials along the sarcolemma. Yes! These action potentials set off a series of events that lead to a contraction.

Myoglobin has a special function in muscle tissue it... A) Breaks down glycogen B) Contractile protein C) Holds a reserve supply of oxygen in the muscle

C) Holds a reserve supply of oxygen in the muscle

Aerobic exercise results in all of the following except... A) More capillaries surrounding muscle fibers B) More mitochondria in muscle cells C) Increased size and strength of existing muscle cells D) More myoglobin

C) Increased size and strength of existing muscle cells

What causes the power stroke? calcium hydrolysis of ATP release of ADP and Pi binding of ATP

C) RELEASE OF ADP AND Pi Yes, the hydrolysis of ATP provides the energy for the power stroke. Energy is transferred from ATP to the myosin head.

The ions that enter the skeletal muscle cell during the generation of an action potential are... A) Calcium ions B) Chloride ions C) Sodium ions D) Potassium ions

C) Sodium ions

Which of the following statements is true? A) Cardiac muscle cells have many nuclei. B) Smooth muscle cells have T tubules. C) Striated muscle cells are long and cylindrical with many nuclei. D) Cardiac muscle cells are found in the heart and large blood vessels.

C) Striated muscle cells are long and cylindrical with many nuclei.

Which of the following describes the cells of single-unit visceral muscle? A) They contract all at once. B) They are chemically coupled to one another by gap junctions. C) They exhibit spontaneous action potentials. D) They consist of muscle fibers that are structurally independent of each other.

C) They exhibit spontaneous action potentials.

The function of the T-tubules in muscle contraction is to... A) Make and store gylcogen B) Release calcium into the cell interior and then pick it up again C) Transmit the actin potential deep into the muscle cells D) Form proteins

C) Transmit the actin potential deep into the muscle cells

Muscle tone is ________. A) the ability of a muscle to efficiently cause skeletal movements B) the feeling of well-being following exercise C) a state of sustained partial contraction D) the condition of athletes after intensive training

C) a state of sustained partial contraction

After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction? A) calcium ions returning to the terminal cisternae B) the tropomyosin blocking the myosin once full contraction is achieved C) acetylcholinesterase destroying the ACh D) the action potential stops going down the overloaded T tubules

C) acetylcholinesterase destroying the ACh

Which results in the formation of lactic acid?

C) anaerobic glycolysis

What is the role of calcium ions in muscle contraction? A) form hydroxyapatite crystals B) reestablish glycogen stores C) bind to regulatory sites on troponin to remove contraction inhibition D) increase levels of myoglobin

C) bind to regulatory sites on troponin to remove contraction inhibition

Which of the following is not a way muscle contractions can be graded? A) changing the frequency of stimulation B) changing the strength of the stimulus C) changing the type of muscle fibers involved in the contraction D) changing the type of neurotransmitter released by the motor neuron

C) changing the type of muscle fibers involved in the contraction

Which of the following is not a usual result of resistance exercise? A) increase in the efficiency of the respiratory system B) increase in the efficiency of the circulatory system C) increase in the number of muscle cells D) increase in the number of myofibrils within the muscle cells

C) increase in the number of muscle cells

Which of the choices below does not describe how recovery oxygen uptake (oxygen deficit) restores metabolic conditions? A) converts lactic acid back into glycogen stores in the liver B) resynthesizes creatine phosphate and ATP in muscle fibers C) increases the level of lactic acid in the muscle D) replaces the oxygen removed from myoglobin

C) increases the level of lactic acid in the muscle

The strongest muscle contractions are normally achieved by ________. A) increasing stimulus above the threshold B) increasing stimulus above the treppe stimulus C) increasing the stimulation up to the maximal stimulus D) recruiting small and medium muscle fibers

C) increasing the stimulation up to the maximal stimulus

Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the events of excitation-contraction coupling occur. A) contraction B) relaxation C) latent D) refractory

C) latent

Which of the following is a factor that affects the velocity and duration of muscle contraction? A) number of muscle fibers stimulated B) size of the muscle fibers stimulated C) load on the fiber D) muscle length

C) load on the fiber

The oxygen-binding protein found in muscle cells is ________. A) hemoglobin B) ATP C) myoglobin D) immunoglobin

C) myoglobin

Rigor mortis occurs because ________. A) the cells are dead B) sodium ions leak out of the muscle C) no ATP is available to release attached actin and myosin molecules D) proteins are beginning to break down, thus preventing a flow of calcium ions

C) no ATP is available to release attached actin and myosin molecules

Which muscle cells have the greatest ability to regenerate? A) skeletal B) cardiac C) smooth D) no muscle can regenerate

C) smooth

Myoglobin ________. A) breaks down glycogen B) is a protein involved in the direct phosphorylation of ADP C) stores oxygen in muscle cells D) produces the end plate potential

C) stores oxygen in muscle cells

The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________. A) actin and myosin interact by the sliding filament mechanism B) the trigger for contraction is a rise in intracellular calcium C) the site of calcium regulation differs D) ATP energizes the sliding process

C) the site of calcium regulation differs

The warm-up period required of athletes in order to bring their muscles to peak performance is called ________. A) twitch B) wave summation C) treppe D) incomplete tetanus

C) treppe

Period of Contraction

cross bridges are active, from the onset to the peak of tension development, and the myogram tracing rises to a peak

Which of the following is true about smooth muscle?

Certain smooth muscle cells can actually divide to increase their numbers

Curare is a poisonous plant extract. Curare molecules have a chemical structure like the neurotransmitter ACh. Curare can bind to the ACh receptor site on the chemically gated ion channels in the motor end plate. Even though curare will bind to the receptor site it will not open the ion channel and no ions will pass through. What do you think the symptoms of curare poisoning would look like? Smooth muscles will become stimulated causing quick movement of nutrients through the digestive system. Muscles will respond too quickly and cause a severe tremor. Curare will only affect cardiac muscle, causing fibrillations of the heart. Curare will only affect muscles with ACh receptors, paralyzing them.

Curare will only affect muscles with ACh receptors, paralyzing them.

Which of the following is the smallest structural unit in which the distinctive striated bands characteristic of skeletal muscle are observed? A B C D

Synaptic vesicles at the neuromuscular junction contain __________. a ACh receptors B synaptic potentials c calcium D acetylcholine

D acetylcholine Acetylcholine (ACh) is the neurotransmitter contained in synaptic vesicles at the neuromuscular junction. ACh allows a motor neuron to stimulate the sarcolemma of a skeletal muscle fiber.

ACh receptors are found mainly in the __________. A synaptic vesicles B axon terminal C terminal cisternae D sarcolemma

D sarcolemma The sarcolemma contains ACh receptors. The opening of these ACh receptors depolarizes the muscle fiber, which leads to the generation of a muscle action potential.

A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected? A) Voltage-gated sodium channels. B) Myosin cross-bridge binding sites. C) Potassium leak channels. D) A series of proteins that control calcium release.

D) A series of proteins that control calcium release. Yes! When action potentials propagate along T-tubules, a voltage-sensitive protein changes shape and triggers a different protein to open it's channels, resulting in the release of calcium from the terminal cisternae.

When does cross bridge cycling end? Cross bridge cycling ends when ATP binds to the myosin head. Cross bridge cycling ends when calcium ions are passively transported back into the sarcoplasmic reticulum. Cross bridge cycling ends when calcium release channels in the sarcoplasmic reticulum open. Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.

D) Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin. The sarcoplasmic reticulum contains Ca2+-ATPases that actively transport Ca2+ into the SR. Without Ca2+, troponin returns to its resting shape, and tropomyosin glides over and covers the myosin binding sites on actin

A smooth, sustained contraction resulting from very rapid stimulation of the muscle, in which no evidence of relaxation is seen, is called... A) A Twitch B) Wave summation C) Multiple motor unit summation D) Fused tetanus

D) Fused Tetanus

The contractile, or functional, unit of a muscle fiber is __________. A) troponin B) the elastic filament C) the myofilament D) the sarcomere

D) The Sarcomere The sarcomere is the contractile unit of a muscle fiber and the smallest functional unit of muscle. A sarcomere is the region of a myofibril between two successive Z discs; it primarily consists of thin and thick myofilaments.

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter? norepinephrine dopamine serotonin acetylcholine (ACh)

D) acetylcholine (ACh) Yes, acetylcholine is the neurotransmitter found in neuromuscular junctions.

Which of the following is not a role of ionic calcium in muscle contraction? A) triggers neurotransmitter secretion B) promotes breakdown of glycogen and ATP synthesis C) removes contraction inhibitor D) activates epinephrine released from adrenal gland

D) activates epinephrine released from adrenal gland

What is the primary mechanism by which ACh is cleared from the synaptic cleft? diffusion away from the synaptic cleft endocytosis by synaptic vesicles reuptake into the synaptic terminal broken down by acetylcholinesterase

D) broken down by acetylcholinesterase Acetylcholinesterase breaks down acetylcholine in the synaptic cleft. Inhibition of acetylcholinesterase, as some poisons can do, causes repeated muscle action potentials and near-constant muscle contraction.

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers? A) Sodium ions. B) Action potentials. C) Acetylcholine. D) Calcium ions.

D) calcium ions Yes! Action potentials propagating down the T-tubule cause a voltage-sensitive protein to change shape. This shape change opens calcium release channels in the sarcoplasmic reticulum, allowing calcium ions to flood the sarcoplasm. This flood of calcium ions is directly responsible for the coupling of excitation to contraction in skeletal muscle fibers.

The main effect of the warm-up period of athletes, as the muscle contractions increase in strength, is to ________. A) increase the myoglobin content B) convert glycogen to glucose C) tone the muscles and stabilize the joints for the workout D) enhance the availability of calcium and the efficiency of enzyme systems

D) enhance the availability of calcium and the efficiency of enzyme systems

Skeletal muscle cells are grouped into bundles called __________. A) muscle fibers B) myofibrils C) myofilaments D) fascicles

D) fascicles Skeletal muscle cells (or muscle fibers) are grouped into fascicles that resemble bundles of stick

During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________. A) a strong base B) stearic acid C) hydrochloric acid D) lactic acid

D) lactic acid

Which of the following would be recruited later in muscle stimulation when contractile strength increases? A) motor units with the longest muscle fibers B) many small motor units with the ability to stimulate other motor units C) large motor units with small, highly excitable neurons D) motor units with larger, less excitable neurons

D) motor units with larger, less excitable neurons

The contractile units of skeletal muscles are ________. A) microtubules B) mitochondria C) T tubules D) myofibrils

D) myofibrils

The major function of the sarcoplasmic reticulum in muscle contraction is to ________. A) make and store phosphocreatine B) synthesize actin and myosin myofilaments C) provide a source of myosin for the contraction process D) regulate intracellular calcium concentration

D) regulate intracellular calcium concentration

Creatine phosphate functions in the muscle cell by ________. A) forming a temporary chemical compound with myosin B) forming a chemical compound with actin C) inducing a conformational change in the myofilaments D) storing energy that will be transferred to ADP to resynthesize ATP

D) storing energy that will be transferred to ADP to resynthesize ATP

What is the most distinguishing characteristic of muscle tissue? A) the design of the fibers B) the sarcoplasmic reticulum C) the diversity of activity of muscle tissue D) the ability to transform chemical energy into mechanical energy

D) the ability to transform chemical energy into mechanical energy

What factor would account for a strong synovial joint? A) small reinforcing ligaments B) low muscle tone C)synovial fluid D) the deepest articular surface

D) the deepest articular surface The deepest articular surface would likely lead to a strong synovial joint.

What is name given to the regularly spaced infoldings of the sarcolemma? A) sarcoplasmic reticulum B) terminal cisternae C) motor endplates D) transverse or T tubules

D) transverse or T tubules Yes! T tubules penetrate a skeletal muscle fiber and provide a pathway for excitation into the interior.

What specific event triggers the uncovering of the myosin binding site on actin? Calcium ions bind to tropomyosin and change its shape. Sodium ions bind to troponin and change its shape. Calcium release channels open in the sarcoplasmic reticulum, and calcium levels rise in the sarcoplasm. Calcium ions bind to troponin and change its shape.

D)Calcium ions bind to troponin and change its shape. The shape change caused by the binding of calcium to troponin shifts tropomyosin away from the myosin binding sites on actin.

The sliding filament model of contraction states that __________. A) during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments no longer overlap B) during contraction, the thin myofilaments slide past the thick myofilaments so that calcium ions can be released from the sarcoplasmic reticulum C) during contraction, the thin myofilaments slide past T tubules so that the Z discs are overlapping D) during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree

D)during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree The sliding filament model of contraction states that during contraction, the thin myofilaments slide past the thick myofilaments so that actin and myosin myofilaments overlap to a greater degree. In a relaxed muscle fiber, the thick and thin myofilaments overlap only at the ends of the A band.

Which of the following is the correct sequence of events for muscle contractions? muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke neurotransmitter release, muscle cell action potential, motor neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments

D)motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments

The thin filaments (actin) contain a polypeptide subunit G actin that bears active sites for myosin attachment. True False

true

The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell? sarcolemma T tubule cytosol terminal cisterns (cisternae) of the sarcoplasmic reticulum

D)terminal cisterns cisternae) of the sarcoplasmic reticulum Yes, calcium is stored in the terminal cisterns (cisternae) of the sarcoplasmic reticulum until it is released by an action potential.

The binding of calcium to which molecule causes the myosin binding sites to be exposed? myosin tropomyosin actin troponin

D)troponin es, when calcium binds to troponin, troponin releases tropomyosin, exposing the myosin binding sites

Name and describe the 4 special functional abilities of muscle that are the basis for muscle response

Excitability; ability to receive and respond to a stimulus on the inside or outside of the body. Contractility; ability to shorten forcibly when adequelty stimulated. Extensibility; ability to be stretched or extended. Elasticity; ability to recoil and resume its resting length after being stretched.

During isotonic contraction, the heavier the load, the faster the velocity of contraction.

False

Muscle contraction will always promote movement of body parts regardless of how they are attached.

False

contains only the actin filaments

I band

Gary was injured in an automobile accident that severed the motor neurons innervating his quadriceps. Even though he has had extensive physical therapy, he is still suffering muscle atrophy. Why is the therapy not working? In sarcopenia, there is a gradual loss of muscle mass as muscle proteins degrade faster than they can be replaced. In myotonic dystrophy, there is a gradual loss of muscle mass as muscle proteins degrade faster than they can be replaced. In Duchenne muscular dystrophy, the muscle enlarges due to fat and connective tissue, but the muscle fibers atrophy and degenerate irreversibly. In myasthenia gravis, fibrous connective tissue replaces the muscle tissue that was lost. When atrophy is complete, fibrous tissue cannot be reversed to muscle tissue. In denervation (disuse) atrophy, fibrous connective tissue replaces the muscle tissue that was lost. When atrophy is complete, fibrous tissue cannot be reversed to muscle tissue.

In denervation (disuse) atrophy, fibrous connective tissue replaces the muscle tissue that was lost. When atrophy is complete, fibrous tissue cannot be reversed to muscle tissue.

Distinguish between direct and indirect muscle attachments and tendon and an aponeurosis

In direct or (FLESHY) attachment the epimysium of the muscle is fused to the periosteum of a bone or perichondrium of cartilage. In indirect attachments the muscles connective tissue wrappings extend beyond the muscle as either a rope like tendon or as a sheet like aponeurosis. A tendon is rope like and aponeurosis sheet like.

muscle fibers

Only skeletal and smooth muscle cells are elongated and referred to as this

Formation of Cross Bridge

Initaited when calcium ions released from SR bind to troponin (This causes tropinin to change shape); Tropomyosin moves away from myosin binding sites on actin allowing myosin head to bind actin and form a cross bridge; Myosin head has to be activated before a cross bridge cycle can begin; ATP combines with myosin head and is hydrolized to ADP and inorganic phosphate (Energy from hydrolozied Atp activates myosin head forcing It to be in cocked position)

Fatigued muscles cells that recover rapidly are the products of ________________

Intense exercise of short duration

Which of the following would be recruited later in muscle stimulation when contractile stimulation strength increases?

Motor units with larger, less excitable neurons

What would happen if acetylcholine was not removed from the synaptic cleft?

Multiple action potentials would occur in the muscle fiber.

Which of the following statements is FALSE? >Skeletal muscle cells have T tubules. >Skeletal muscle cells use creatine phosphate instead of ATP to do work. >Skeletal muscle cells are multinucleated. >Skeletal muscle cells contain myoglobin. >Skeletal muscle cells have glycosomes

Muscle cells, just like other cells, use ATP to do work. Creatine phosphate is used by muscle cells to directly phosphorylate (i.e., donate a high-energy phosphate group to) ADP to resynthesize ATP.

velocity and duration of contraction is influenced by

Muscle fiber type Load Recruitment

How can muscle placement result in maximal range?

Muscle inserted closer to a joint will have greater range of motion

How can muscle placement produce maximal strength?

Muscle inserted farther away from a joint will have a more powerful contraction

Extra oxygen that must be taken into the body to oxidize the lactic acid formed during exercise

Oxygen Debt

anaerobic threshold

Point at which muscle metabolism converts to anaerobic

What role does tropomyosin play in the cross bridge cycle?

The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form.

Which of the following is most accurate?

Muscle tension remains relatively constant during isotonic contraction.

Muscle tissue has all of the following properties except ________. a) secretion b) extensibility c) contractility d) excitability

If both motor neurons shown in this figure were to develop action potentials and stimulate muscle fibers, would all the muscle cells shown here contract? No, because neurons in this figure do not innervate every muscle cell shown. Yes, because an entire muscle only needs one neuron to stimulate it in order to contract. Yes, because signals can be passed from stimulated muscle fibers to unstimulated ones. No, because it is impossible for more than one motor unit to contract at once.

No, because neurons in this figure do not innervate every muscle cell shown.

The region between which two points corresponds to the I band? 3 and 5 2 and 5 2 and 3 None of the listed responses is correct.

None of the listed responses is correct.

When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands do not diminish in length.

true

Aaron arrived at the hospital with the following symptoms: drooping eyelids; fatigue and weakness of his muscles; and difficulty talking, breathing, and swallowing. What was his diagnosis?

Myasthenia gravis

The contractile units of skeletal muscles are ________.

Myofibrils

This is a graphic reading of the mechanical contractile activity of a muscle fiber

Myogram

3. ) The thicker filaments are the ----- filaments.

Myosin

BMD (2,3-butanedione 2-monoximime) inhibits myosin, such that ATP can bind to myosin but myosin is unable to hydrolyze the bound ATP. What effect would BMD have on the cross bridge cycle?

Myosin heads would remain detached, unable to cock.

A myosin molecule in the thick filaments can be considered a protein having a quaternary structural level. Which of the following best describes this structural level?

Myosin molecules consists of 2 heavy and 2 light polypeptide chains.

If a muscle fiber were to suddenly and permanently stop producing ATP the fiber would no longer be able to actively transport calcium out of the cytoplasm (sarcoplasm) and the intracellular calcium concentration would rise. Which of the following would you expect to happen?

Myosin would be able to bind to the exposed binding sites on thin filaments but it would not be able to detach.

Rigor mortis occurs because proteins are beginning to break down, thus preventing a flow of calcium ions no ATP is available to release attached actin and myosin molecules sodium ions leak into the muscle causing continued contractions the cells are dead

No ATP is available to release attached actin and myosin molecules

Rigor mortis occurs because ________.

No ATP is available to release the attached actin and myosin molecules.

what happens to sarcomere during contraction

Pulls Z discs toward M line, I bands shorten; Z discs closer; H zones disappear; A bands move closer to each other

myofilaments in smooth muscle

Ratio of thick to thin filaments (1:13) is much lower than in skeletal muscle (1:2)

A) Slow (oxidative), fatigue-resistant fibers

Red fibers, the smallest of the fiber types. A) Slow (oxidative), fatigue-resistant fibers B) Fast (oxidative or glycolytic), fatigable fibers

When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?

Refractory period

T Tubules

Regularly spaced infoldings of sarcolemma that branch extensively throughout the muscle fiber; At numerous junctions, make contact with calcium storing membranous network known as sarcoplasmic reticulum

Rigor mortis occurs because ________. a) the cells are dead b) sodium ions leak into the muscle causing continued contractions c) no ATP is available to release attached actin and myosin molecules d) proteins are beginning to break down, thus preventing a flow of calcium ions

Ca2+ in smooth muscle

SR stores some Ca2+ but most comes from extracellular origins

The smallest contractile unit of a muscle fiber is a

Sacromere

Calcium are at rest here; called enoplasmic reticulum in most cells

Sacroplasmic Reticulum

What structure in skeletal muscle cells functions in calcium storage?

Sarcoplasmic reticulum

What structure in skeletal muscle cells functions in calcium storage? mitochondria myofibril network sarcoplasmic reticulum intermediate filament network

Sarcoplasmic reticulum

Muscle tissue has all of the following properties except extensibility excitability contractility secretion

Secretion

Excitation-Contraction Coupling

Sequence of events that convert s action potentials in a muscle fiber to a contraction; Action potential travels across entire sarcolemma; occur during hidden (laten) period, between AP initiation and the beginning of mechanical activity (contraction); electrical signal does not act directly on myofilaments (it causes rise in intracellular calcium ion concentration that allows filaments to slide)

Characteristics of isometric contractions include all but

Shortening

Which of the following statements is FALSE?

Skeletal muscle cells use creatine phosphate instead of ATP to do work

Which of the following statements is FALSE? Skeletal muscle cells contain myoglobin. Skeletal muscle cells have T tubules. Skeletal muscle cells use creatine phosphate instead of ATP to do work. Skeletal muscle cells have glycosomes. Skeletal muscle cells are multinucleated.

Skeletal muscle cells use creatine phosphate instead of ATP to do work.

Which of the following is true?

Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not

Which of the following is true? Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not. Smooth muscle lacks the thin and thick filaments characteristic of skeletal muscle. Skeletal muscle fibers tend to be shorter than smooth muscle fibers. Skeletal muscle lacks the coarse connective tissue sheaths that are found in smooth muscle.

Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not.

Of the following items listed below, which is the best description for why skeletal muscle stores glycogen The glycogen is an insulating layer that helps regulate body temperature. Skeletal muscle is a heavy consumer of energy. Glycogen provides a smooth surface for filaments to slide on. Glycogen is part of muscles rigid supporting framework.

Skeletal muscle is a heavy consumer of energy.

Of the following items listed below, which is the best description for why skeletal muscle stores glycogen. Skeletal muscle is a heavy consumer of energy. Glycogen is part of muscles rigid supporting framework. Glycogen provides a smooth surface for filaments to slide on. The glycogen is an insulating layer that helps regulate body temperature.

Skeletal muscle is a heavy consumer of energy.

Explain the sliding filament theory of contraction

States that during contraction the thin filaments slide past the thick ones so that actin and myosin filaments overlap to a greater degree. In a relaxed muscle fiber the thick and thin filaments overlap only at the ends of the A band.

What happens to the A band in a contraction?

Stays the same

Myoglobin

Stores oxygen in muscle cells

Creatine phosphate functions is the muscle cell by......?

Storing energy that will be transferred to ADP to resynthesize ATP

Which of the following statements is true?

Striated muscle cells are long and cylindrical with many nuclei.

When a sarcomere contracts and thin filaments move over thick filaments you would expect to see ________.

The I bands to appear smaller

What is the most distinguishing characteristic of muscle tissue? It is composed of multiple cells working together. The ability to transform chemical energy into mechanical energy to move the body Its cells' in ability to reproduce by mitosis The ability to respond to nervous stimulation

The ability to transform chemical energy into mechanical energy

What is the most distinguishing characteristic of muscle tissue?

The ability to transform chemical energy into mechanical energy to move the body

tendon The dense connective tissue at A is continuous with the tendon that connects the muscle to a bone or, in some cases, to another muscle or to the skin.

The connective tissue that covers structure A is continuous with which of the following? synovial membrane ligament tendon endomysium

The contractile units of skeletal muscles are ________. a) T tubules b) microtubules c) mitochondria d) myofibrils

The nurse encourages the patient to do his own activities of daily living such as bathing, eating, and dressing activities. How do these activities promote physical conditioning?

The contraction of the muscles in these activities helps maintain the shape, size, and strength of muscles, as well as joint mobility.

The nurse encourages the patient to do his own activities of daily living such as bathing, eating, dressing, and toileting activities. How do these activities promote physical conditioning? The contraction of the muscles in these activities reverses myotonic dystrophy and rebuilds muscle mass. It does not. Only weight-bearing exercises maintain the shape, size and strength of muscles. The contraction of the muscles in these activities helps maintain the shape, size, and strength of muscles, as well as joint mobility. The contraction of the muscles in these activities reverses sarcopenia and rebuilds muscle mass.

The contraction of the muscles in these activities helps maintain the shape, size, and strength of muscles, as well as joint mobility.

What role does tropomyosin play in the cross bridge cycle? Tropomyosin binds to calcium, causing muscle relaxation. Tropomyosin pushes the myosin head away, causing cross bridge detachment. The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form. Tropomyosin moves the actin filament relative to the myosin filament.

The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form. Tropomyosin covers active sites in relaxed muscle. When tropomyosin is displaced, the active sites are exposed for cross bridge formation.

Based on what you know of the relationship between the thick and the thin filaments, what would happen if a disorder existed that caused a person to produce no tropomyosin?

The muscle tissue would never be able to relax

What result would be expected if an additional stimulus, equal in intensity to the first, were to be applied to the muscle at the 60 millisecond (ms) time point? (see figure 6) The muscle would quickly return to the fully relaxed state of minimum tension. The tension exerted by the muscle would continue to decrease, but at a significantly slower rate than observed without the second stimulus. Tension would increase to the same maximum force measured at the beginning of phase C. The muscle would increase in tension to a level greater than that measured at the beginning of phase C.

The muscle would increase in tension to a level greater than that measured at the beginning of phase C.

The runners' use of stored oxygen, glucose and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake.

The 100 meter dash is a quick and short run requiring explosive speed. On completion of the dash the runners will continue to breathe hard for several seconds to minutes even though they are no longer running. Which of the following is the best explanation for why this is so? Since the exercise was mostly aerobic exercise, the runners' bodies have not yet realized the run is over. The runners' use of stored oxygen, glucose and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake. The runners' fast oxidative muscles are so slow to utilize oxygen it only begins aerobic respiration by the time the run has finished. Slow oxidative fibers are recruited last and have only started to work at completion of the run.

The runners' use of stored oxygen, glucose and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake.

B) Wave summation -Temporal aka wave summation, occurs because the second contraction occurs before the muscle has completely relaxed.

The situation in which contractions become stronger due to stimulation before complete relaxation occurs. A) Tetanus B) Wave summation C) Muscle Tone D) Multiple motor unit summation E) Maximal stimulus

1 and 7 The distance between points 1 and 7 spans a sarcomere, the smallest contractile unit of a muscle fiber.

The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure? 1 and 7 3 and 5 1 and 3 2 and 6

E) Maximal stimulus -The strongest stimulus that produces increased contractile force.

The stimulas above which no stronger contraction can be elicited, because all motor units are firing in the muscle. A) Tetanus B) Wave summation C) Muscle Tone D) Multiple motor unit summation E) Maximal stimulus

a) Epimysium -"outside the muscle" -An "overcoat" of dense irregular connective tissue that surrounds the whole muscle.

The tissue that binds muscles into functional groups. Connective tissue covering the exterior of a muscle organ. a) Epimysium b) Endomysium c) Muscle Fiber d) Fascicle e) Perimysium

During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases?

There are always some myosin heads attached to the actin myofilament when other myosin heads are detaching.

Which of the following describes the cells of unitary smooth muscle?

They exhibit spontaneous action potentials.

The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily.

True

The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily. True or False

True

The force of muscle contraction is controlled by multiple motor unit summation or recruitment.

True

Tetanus

This is when muscle contractions fuse together into a smooth sustained contraction

Excess Postexercise Oxygen Consumption (EPOC)

To return muscle to resting state: Oxygen reserves replenished, Lactic acid converted to pyruvic acid, Glycogen stores replaced, ATP and creatine phosphate reserves replenished

What is the warm up period before you exercise to increase the availability of calcium ion?

Treppe

What is the role of tropomyosin in skeletal muscles?

Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

How does troponin facilitate cross bridge formation?

Troponin controls the position of tropomyosin on the thin filament, enabling myosin heads to bind to the active sites on actin.

A contraction in which the muscle does not shorten but its tension increases is called isometric.

True

A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell.

True

Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments.

True

Cardiac muscle has a limited regenerative capacity. T or F?

True

Contractures are a result of a total lack of ATP.

True

Eccentric contractions are more forceful than concentric contractions.

True

Peristalsis is characteristic of smooth muscle.

True

Single-unit smooth muscle is found in the intestines.

True

Smooth muscles relax when intracellular Ca2+ levels drop but may not cease contractions.

True

T or F? In the muscles of the limbs, the origin is usually the immobile muscle attachment

True

T or F? Isometric contractions are important contractions that allow humans to hold their posture over time

True

What does excess postexercise oxygen consumption represent? a) amount of oxygen needed for aerobic activity to accomplish the same amount of work b) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used c) the amount of oxygen taken into the body immediately after the exertion d) the amount of oxygen equal to the oxygen already used

What is the functional unit of a skeletal muscle called? a) a sarcomere b) the sarcoplasmic reticulum c) a myofilament d) a myofibril

the ability to transform chemical energy into mechanical energy to move the body

What is the most distinguishing characteristic of muscle tissue? it is composed of multiple cells working together the ability to transform chemical energy into mechanical energy to move the body its cells' in ability to reproduce by mitosis the ability to respond to nervous stimulation

What is the most distinguishing characteristic of muscle tissue? a) the ability to respond to nervous stimulation b) it is composed of multiple cells working together c) its cells' in ability to reproduce by mitosis d) the ability to transform chemical energy into mechanical energy to move the body

What is the role of tropomyosin in skeletal muscles? a) Tropomyosin is the receptor for the motor neuron neurotransmitter. b) Tropomyosin is the chemical that activates the myosin heads. c) Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules. d) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

What part of the sarcolemma contains acetylcholine receptors? a) end of the muscle fiber b) part adjacent to another muscle cell c) motor end plate d) any part of the sarcolemma

What structure in skeletal muscle cells functions in calcium storage? a) mitochondria b) myofibrillar network c) sarcoplasmic reticulum d) intermediate filament network

Which muscle cells have the greatest ability to regenerate? a) smooth b) skeletal c) no muscle can regenerate d) cardiac

B A fascicle is an organized group of muscle fibers (cells) bounded by a perimysium.

Which of the following corresponds to a single fascicle? A B C D

secreting hormones

Which of the following is NOT a normal function of muscle tissue? maintaining posture stabilizing joints generating heat producing movement secreting hormones

the region between 2 and 3 Actin and myosin are components of thin and thick filaments, respectively. The region between points 2 and 3 includes the area of overlap between thin and thick filaments.

Which of the following regions best identifies where myosin would have maximum cross-bridge access to actin? the region between 1 and 2 the region between 3 and 5 4 the region between 2 and 3

Which of the following statements is true? a) Smooth muscle cells have T tubules. b) Skeletal muscle cells are long and cylindrical with many nuclei. c) Cardiac muscle cells are found in the heart and large blood vessels. d) Cardiac muscle cells have many nuclei.

Which of the following surrounds the individual muscle cell? a) perimysium b) fascicle c) epimysium d) endomysium

The structure at B is covered by the perimysium. Remember that the word root peri means "around," as in "perimeter."

Which of the structures is surrounded by the connective tissue sheath known as the perimysium? A B C D

C Note that a skeletal muscle cell is commonly termed a muscle fiber.

Which structure in the figure corresponds to a single skeletal muscle cell? A B C D

muscle fiber Skeletal muscle cells fuse during development to form the mature, multinucleated muscle fibers.

Which term best identifies a muscle cell? myofibril sarcomere muscle fiber muscle fascicle

b) H zone -From the German "Heller", bright). Named for their properties under a polarization microscope. -Thick filaments only.

Within the A-band is a polar region called the ___. (a) Z disc b) H zone c) I band d) A band e) M line

b) Endomysium -A whispy sheath of connective tissue that surrounds each individual muscle fiber. It consists of fine areolar connective tissue.

Within the muscle. Connective tissue sheath surrounding individual muscle fibers. a) Epimysium b) Endomysium c) Muscle Fiber d) Fascicle e) Perimysium

A sarcomere is the distance between two

Z discs

Aponeurosis

a flat sheet of DFCT muscle to muscle

Myogram

a graphic recording of contractile activity; line recording activity is called tracing

Most skeletal muscles contain ________.

a mix of fiber types

Most skeletal muscles contain ________.

a mixture of fiber types

Cross bridge formation between myosin heads and actin molecules is caused by the elevation of calcium ion concentration in the cytosol. During rigor mortis, this elevation of calcium ion concentration in the cytosol is permanent because ________. a)mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps b)troponin molecules bind irreversibly to calcium ions to prevent them from being removed from the cytosol c)tropomyosin molecules bind irreversibly to calcium ions to prevent them from being removed from the cytosol d)acetylcholine continues to stimulate the release of calcium ions from the sarcoplasmic reticulum

a)mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps

Synaptic vesicles at the neuromuscular junction contain __________.

acetylcholine

The neurotransmitter released by somatic motor neurons is

acetylcholine

acetylcholine receptors in the motor end plate

Although all the anatomical parts of muscle work together to give it its characteristics, which of the following proteins listed below would be most associated with the characteristics of excitability?

acetylcholine receptors in the motor end plate

After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?

acetylcholinesterase destroying the ACh

After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction? acetylcholinesterase destroying the ACh calcium ions returning to the terminal cisternae the tropomyosin blocking the myosin once full contraction is achieved the action potential stops going down the overloaded T tubules

acetylcholinesterase destroying the ACh

Which protein is indicated by the letter A? (see figure 4) myosin keratin actin troponin

actin

myofilaments

actin (thin filaments) and myosin (thick filaments)

The sliding filament model of contraction involves the Z discs sliding over the myofilaments actin and myosin lengthening in order to slide past each other actin and myosin sliding past each other and partially overlapping the shortening of thick filaments so that thin filaments slide past

actin and myosin sliding past each other and partially overlapping

The sliding filament model of contraction involves ________.

actin and myosin sliding past each other and partially overlapping

During muscle contraction, myosin cross bridges attach to which active sites?

actin filaments

Excitation-Contraction Coupling: Step 1

action potential travels across entire sarcolemma and are rapidly conducted to interior of muscle fibers by transverse tubules

A metabolic pathway that provides for a large amount of ATP per glucose because oxygen is used. Products are water and carbon dioxide and ATP.

aerobic respiration

Fused or Complete Tetanus

as the stimulation frequency continues to increase, muscle tension increases until a maximal tension is reached; at this point all evidence of muscle relaxation dissapears and the contractions fuse into a smooth, sustained contraction plateau

What is the role of calcium in the cross bridge cycle? Calcium binds to myosin, causing the myosin head to release from the actin myofilament. Calcium binds to troponin, altering its shape. Calcium binds to active sites on actin, forming the cross bridge. Calcium binds to troponin, exposing the active site on troponin.

b) Calcium binds to troponin, altering its shape. Calcium binding to troponin causes tropomyosin to move away from the active sites on actin.

When the chemically gated ion channels open, which ion is mainly responsible for depolarizing the sarcolemma? ACh sodium calcium potassium

b) SODIUM The inward diffusion of sodium ions, through acetylcholine receptors, depolarizes the sarcolemma. Potassium also diffuses through acetylcholine receptors, but less potassium diffuses than sodium, and the outward movement of potassium is not depolarizing

What would happen if acetylcholine was not removed from the synaptic cleft? Multiple action potentials would occur in the motor neuron. Multiple action potentials would occur in the muscle fiber. Voltage-gated Ca2+ channels would remain open. The acetylcholine receptors would not open.

b) action potentials would occur in the muscle fiber. Action potentials will not cease until acetylcholine is removed from the synaptic cleft. Therefore, the constant presence of acetylcholine would cause multiple muscle action potentials and near-constant muscle contraction.

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft? a protein carrier exocytosis a channel

b)exocytosis the synaptic vesicles (where the neurotransmitter is stored) merge with the membrane and release the neurotransmitter by exocytosis

b, d, f, a, e, c

The deltoid is a prime mover of the arm that acts in adduction.

false

An enzyme known as acetylcholinesterase is present in the synaptic cleft. What is its role?

break down acetylcholine

What is the primary mechanism by which ACh is cleared from the synaptic cleft?

broken down by acetylcholinesteras

What is the primary mechanism by which ACh is cleared from the synaptic cleft?

broken down by acetylcholinesterase

A nursing infant develops a powerful sucking muscle that adults also use for whistling. What is this muscle called?

buccinator

A fascicle is a

bundle of muscle fibers enclosed by a connective tissue sheath

An enzyme known as acetylcholinesterase is present in the synaptic cleft. What is its role? to facilitated transport of acetylcholine across the cleft to facilitate the entrance of acetylcholine into the muscle cell to break down acetylcholine to pump Ca2+ back out of the axon terminal

c) TO BREAK DOWN ACETYLCHOLINE

Excitation-Contraction Coupling (3)

calcium binds to tropinin and removes the blocking action of tropomyosin; when Ca2+ binds, troponin changes shape, exposing binding sites for myosin on the thin filaments

What most directly causes synaptic vesicles to release acetylcholine into the synaptic cleft?

calcium entering the axon terminal

Normally stored in the terminal cisternae of the sarcoplasmic reticulum.

calcium ions

Serves as the actual ʺtriggerʺ for muscle contraction by removing the inhibition of the troponin molecules.

calcium ions

In an isotonic contraction, the muscle ________. does not change in length but increases tension rapidly resynthesizes creatine phosphate and ATP never converts pyruvate to lactate changes in length and moves the "load"

changes in length and moves the "load"

indirect skeletal muscle attachment

connective tissue wrappings extend beyond muscle as rope like tendon or sheetlike aponeurosis (white part of muscle man's head that attaches muscles)

contractures

continuous muscle contractions because you cannot detach myosin heads from actin because there is a lack of ATP

myofibril

contractile unit of skeletal muscle

what functional characteristic is unique only to muscles?

contractility

Excitation-Contraction Coupling (4)

contraction begins; myosin binding to actin forms cross bridges and contraction begins; at this point E-C coupling is over

wave summation

contractions become stronger due to stimulation before complete relaxation occurs

Recruitment (Multiple Motor Unit Summation)

controls force of contraction; achieved by delivering shocks of increasing voltage to the muscle, calling more and more muscle fibers to play

recruitment

controls force of contraction; more motor neurons are firing

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open? chemically gated calcium channels voltage-gated sodium channels voltage-gated potassium channels voltage-gated calcium channels

d)voltage-gated calcium channels Yes, the action potential opens voltage-gated calcium channels and calcium rushes into the axon terminal, leading to the release of the neurotransmitter.

Skeletal muscle cells are grouped into bundles called __________.

fascicles

In a bedridden patient recovering from a badly fractured femur, disuse atrophy in the thigh muscles is caused by _________. decreased ability of muscle cells to produce ATP, resulting in decreased ability of the muscles to contract decreased ability to synthesize acetylcholine in the neurons that innervate the thigh muscles decreased synthesis of muscle proteins and/or increased breakdown of muscle proteins none of the above

decreased synthesis of muscle proteins and/or increased breakdown of muscle proteins

epimysium

dense irregular connective tissue surrounding entire muscle; may blend with fascia

What event directly triggers the release of neurotransmitter shown in A? (see figure 3) diffusion of K+ into the axon terminal diffusion of Na+ into the axon terminal diffusion of Ca2+ into the axon terminal diffusion of Na+ out of the axon terminal

diffusion of Ca2+ into the axon terminal

Which pathway for regenerating ATP is the most inefficient during 30 minutes of light to moderate exercise?

direct phosphorylation of ADP by creatine phosphate

fascicle

discrete bundle of skeletal muscle fibers segregated from the rest of the muscle by a connective tissue sheath (perimysium)

The sliding filament model of contraction states that __________.

during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree

The sliding filament model of contraction states that

during contraction, the thing myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree

Where in the cross bridge cycle does ATP hydrolysis occur?

during the cocking of the myosin head

elastic (titin) filaments

Action Potential

electrical charge which occurs along the entire surface of the sarcolemma; 3 steps involved for this to occur

Which of the following surrounds the individual muscle cell?

endomysium

What is the functional role of the T tubules?

enhance cellular communication during muscle contraction

What is the functional role of the T tubules? a synthesize ATP to provide energy for muscle contraction hold cross bridges in place in a resting muscle enhance cellular communication during muscle contraction stabilize the G and F actin

enhance cellular communication during muscle contraction

Muscle tissue can be stimulated by the nervous system. Cells with the ability to change their membrane potential have what property?

excitability

What cellular event is indicated by A? (see figure 3) active transport facilitated diffusion endocytosis exocytosis

exocytosis

A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate.

false

Although all skeletal muscles have different shapes, the fascicle arrangement of each muscle is exactly the same.

false

Muscles that help to maintain posture are best described as synergists.

false

Once a motor neuron has fired, all the muscle fibers in a muscle contract.

false

Addition of more mitochondria to a muscle fiber will have the least effect on ________.

fast-glycolytic fibers

perimysium

fibrous connective tissue surrounding fascicles (groups of muscle fibers)

Period of Relaxation

final phase, lasting 10-100ms, is initiated by reentry of Ca2+ into the SR; muscle tension decreases to zero and tracing returns to baseline

endomysium

fine areolar connective tissue surrounding each muscle fiber (cell)

Isotonic

force overcomes the load & muscles actually contract

Terminal Cisternae

formed by SR (On portion of t tubule and adjacent terminal cisternae); saclike bulges where it abuts t tubules

A smooth, sustained contraction resulting from very rapid stimulation of the muscle, in which no evidence of relaxation is seen is called

fused tetanus

At the grocery store a cute, little curly-haired child is standing behind you in line. You turn around for a moment and she sticks her tongue out at you. Which tongue muscle did she use?

genioglossus

An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.

glycolysis

An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________. hydrolysis glycolysis the citric acid cycle the electron transport chain

glycolysis

Myoglobin has a special function in muscle tissue, it

holds a reserve supply of oxygen in the muscle

Isometric

if muscle tension develops but the load is not moved; increasing muscle tension is measured

Isotonic

if the muscle tension developed overcomes the load and muscle shortening occurs; amount of muscle shortening is measured

Unfused or Incomplete Tetanus

if the stimulus strength is held canstant and the muscle is stimulated at an increasingly faster rate, the relaxation time between the twitches become shorter and shorter, the concentration of Ca2+ in the cytosol higher and higher, and the degree of wave sumation greater and greater, progressing to a sustained but quivering contraction

Temporal/Wave Summation

if two identical stimuli (electrical shocks or nerve impulses) are delivered to muscle in rapid succession, the second twitch will be stronger then the first; temoral or wave summation is this second twitch; this occurs because second contraction occurs before the muscle has completely relaxed; primary function is to produce smooth continous muscle cells

Aerobic exercise results in all of the following except

increased size and strength of existing muscle cells

The strongest muscle contractions are normally achieved by ________.

increasing the stimulation up to the maximal stimulus

The strongest muscle contractions are normally achieved by ________. recruiting small and medium muscle fibers increasing stimulus above the threshold increasing the stimulation up to the maximal stimulus increasing stimulus above the treppe stimulus

increasing the stimulation up to the maximal stimulus

Myasthenia gravis is sometimes treated medically by a treatment that involves _______

inhibiting the action of acetylcholinesterase

Myasthenia gravis is sometimes treated medically by a treatment that involves ________. boosting the activity of the immune system suppressing the release of acetylcholine from synaptic vesicles suppressing the synthesis of acetylcholine inhibiting the action of acetylcholinesterase

inhibiting the action of acetylcholinesterase

tropomyosin

inhibits myosin attachment to actin

Contractures

lack in ATP; states of continuous contraction because the cross bridges are unable to detach

smooth muscle and connective tissue

lacks connective tissue sheaths, only has endomysium

During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________.

lactic acid

During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________. stearic acid a strong base hydrochloric acid lactic acid

lactic acid

Immediately following the arrival of the stimulus at the axon terminal of a motor neuron there is a short period called the ________ period during which the neurotransmitter is released by exocytosis, diffuses across the synaptic cleft, and binds to its receptors.

latent

Three phases of muscle twitch

latent period period of contraction period of relaxation

Sarcolemma

like plasma membrane polarized; their is a potential voltage difference across the membrane and the inside is negative relative to the outer membrane face

Which of the following is a factor that affects the velocity and duration of muscle contraction?

load on the fiber

Which of the following factors influence the velocity and duration of muscle contraction?

load placed on the muscle

Approximately 80% of a muscle fiber's volume are the myofibrils. This characteristic reflects muscles ability to ________.

produce movement through contractile force

Anearobic Pathway (Glycolosis)

metabolic pathway without oxygen; produced 4 ATP; 10 step process; every step is a chemical reaction and changes everytime (10 times); 1st 5 steps are known as energy investment phase (they require energy) [2 ATPS to produce these 5 steps]; 2nd Stages known as Reinvestment stage; makes only 2 ATPs; this process occurs in cytoplasm of cell; 2 energy sources glucose and glycogen; makes 2 or 3 ATP + 2 Pyruvic acids

What is a Threshold?

minimal or smallest stimulus needed to produce a response

mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps

Cross bridge formation between myosin heads and actin molecules is caused by the elevation of calcium ion concentration in the cytosol. During rigor mortis, this elevation of calcium ion concentration in the cytosol is permanent because ________. mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps troponin molecules bind irreversibly to calcium ions to prevent them from being removed from the cytosol tropomyosin molecules bind irreversibly to calcium ions to prevent them from being removed from the cytosol acetylcholine continues to stimulate the release of calcium ions from the sarcoplasmic reticulum

mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps

What level of structural organization do voltage-gated sodium channels in muscle sarcolemma represent?

molecule

Part of muscle fibers sacrolemma located in close proximity to the axon terminals of the motor end plate

motor end plate

What part of the sarcolemma contains acetylcholine receptors?

motor end plate

What part of the sarcolemma contains acetylcholine receptors? end of the muscle fiber motor end plate any part of the sarcolemma part adjacent to another muscle cell

motor end plate

Which of the following is the correct sequence of events for muscle contractions?

motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments

Each neuron shown in this figure innervates a group of muscle fibers. What is the term for a group of muscle fibers innervated by a single neuron? (see figure 5) neuromuscular junction sarcomere fascicle motor unit

motor unit

Which of the following would be recruited later in muscle stimulation when contractile strength increases?

motor units with larger, less excitable neurons

troponin

moves tropomyosin from actin active sites and allows myosin to bind

How a smooth increase in muscle force is produced.

multiple motor unit summation

organization of skeletal muscle

muscle (organ) fascicle (bundles of muscle fibers) muscle fibers (muscle cell) myofibrils (actin and myosin inside of cells)

Graded Muscle Responses

muscle contraction can be graded in two ways: (1) by changing the frequency of stimulation and (2) by changing the strength of stimulation

Beyond threshold

muscle contracts more vigorously as stimulus strength is increased due to recruitment(multiple motor unit summation).

Which term best identifies a muscle cell?

muscle fiber

refractory period

muscle fiber cannot be stimulated for a specific amount of time, until repolarization is complete

Isotonic Contractions

muscle length changes and moves the load, the tension remains relatively constant through the rest of the contractile period; come in two flavors concentric and eccentric

threshold stimulus

muscle response to stimulus strength causing first observable muscle contraction

Prime Mover

muscle that bears the major responsibility for a particular movement

What, specifically, is a cross bridge?

myosin binding to actin

The thicker filaments are the

myosin filaments

The sites where the motor nerve impulse is transmitted from the nerve endings to the skeletal muscle cell membranes are the

neuromuscular junctions

Rigor mortis occurs because ________.

no ATP is available to release attached actin and myosin molecules

latent period

no muscle tension; period of time between excitation and contraction

subthreshold stimuli

no observable contractions

Duchenne muscular dystrophy could theoretically be cured if a technique was developed that would _________. strengthen the dystrophin proteins that are present in the patient's muscle fibers double the existing number of dystrophin molecules in the patient's muscle fibers strengthen the thick and thin filaments in the patient's muscle fibers none of the above

none of the above

Duchenne muscular dystrophy could theoretically be cured if a technique was developed that would _________.

none of the above Without a normal copy of DNA for transcription, there can never be a normal protein translated.

synaptic vessels

of axon terminal contain acetylcholine

junctional folds

of sarcolemma contain ACh receptors

myoglobin

oxygen binding protein found in muscle cells

sarcolemma

plasma membrane of muscle fiber

resting sarcolemma

polarized (negative) -90mV

What is the primary function of wave summation?

produce smooth, continuous muscle contraction

What is the primary function of wave summation? prevent muscle fatigue prevent muscle relaxation increase muscle tension produce smooth, continuous muscle contraction

produce smooth, continuous muscle contraction

What is the function of the filaments found in ranges 1-2 and 6-7 but no other ranges? (see figure 2) neurological sensing of the muscle's tension adding strength to contraction protection from overstretching a connection between the myosin fibers and a calcium source

protection from overstretching

calmodulin

protein that binds Ca2+ in smooth muscle because there is no troponin

Z disc

proteins that anchor thin filaments (Actin)

Cross Bridge Cycle: Step 4

reactivation of myosin head: ATP hydrolized to ADP and inorganic phospahte; Energy released during hydrolizes reactivates myosin head returning it to cocked postion

If both of the neurons in the figure were activated, more muscle fibers would contract than if either neuron alone were active. This mechanism for control of the force of muscle contraction is known as __________. (see figure 5) excitation-contraction coupling wave summation tetanus recruitment

recruitment

When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?

refractory period

what is the neuromuscular?

region of contact between motor neuron and muscle fiber (includes axon terminal, synaptic cleft, and motor end plate)

Slow oxidative muscle fibers are best suited for

running a marathon

Slow oxidative muscle fibers are best suited for __________.

running a marathon

Slow oxidative muscle fibers are best suited for __________.

running a marthaon

The __________ shorten(s) during muscle contraction

sacromere

ACh receptors are found mainly in the __________.

sarcolemma

The __________ shorten(s) during muscle contraction

sarcomere

The ______________ shorten(s) during muscle contraction

sarcomere

The contractile, or functional, unit of a muscle fiber is __________.

sarcomere

Red fibers, the smallest of the fiber types.

slow (oxidative fatigue resistant fibers)

List the characteristics of a Red Band

slow contracting unity; smaller diameter; more mitochondria; fatigue resistant

If given the exact same amount of ATP, which of the three fiber types would be able to contract for the longest amount of time?

slow oxidative fibers

Reduction in blood flow to a muscle fiber would have the greatest effect on ________.

slow oxidative fibers

Which muscle type is responsible for this vasodilation?

smooth muscle

which muscle cell regenerates

smooth muscle cell

When the chemically gated ion channels open, which ion is mainly responsible for depolarizing the sarcolemma?

sodium

The ions that enter the skeletal muscle during action potential generation are

sodium ions

Tropomyosin

spirals around actin & blocks active sites of actin

Subthreshold Stimulus

stimuli that produce no observable contractions

creatine

stores energy that will be used by ADP to create ATP

Myoglobin ________.

stores oxygen in muscle cells

Myoglobin Is a portion involved in the direct phosphorylation of ADP produces the end plate potential breaks down glycogen stores oxygen in muscles cells

stores oxygen in muscles cells

Creatine phosphate functions in the muscle cell by ________.

storing energy that will be transferred to ADP to resynthesize ATP

Creatine phosphate functions in the muscle cell by ________. forming a chemical compound with actin storing energy that will be transferred to ADP to resynthesize ATP forming a temporary chemical compound with myosin inducing a conformational change in the myofilaments

storing energy that will be transferred to ADP to resynthesize ATP

What feature of smooth muscle allows it to stretch without immediately resulting in a strong contraction?

stress-relaxation response

The connective tissue that covers structure A is continuous with which of the following?

tendon

The connective tissue that covers structure A is continuous with which of the following? (see figure 1)

tendon

Isometric Contractions

tension may build to the muscles peak tension producing capacity, but the muscle neither shortens nor lengthens; occur when a muscle attempts to move a load that is greater then the force (tension) the muscle is able to develop

Continued sustained smooth contraction due to rapid stimulation.

tetanus

When a sarcomere contracts and thin filaments move over thick filaments you would expect to see ________.

the I bands to appear smaller

What is the most distinguishing characteristic of muscle tissue?

the ability to transform chemical energy into mechanical energy to move the body

The force of a muscle contraction is NOT affected by

the amount of ATP stored in the muscle cells

The force of a muscle contraction is NOT affected by __________.

the amount of ATP stored in the muscle cells

Oxygen Deficit

the extra amount of oxygen that the body must take in for these restorative processes

Latent Period

the first few milliseconds following stimulation when excitation-contraction coupling is occuring; during this period, muscle tension is beggining to increase

Muscle Tension

the force exerted by a containing muscle on an object

Aerobic Endurance

the length of time a muscle can continue to contract using aerobic pathways

A toxin released by certain bacteria can block the release of neurotransmitters into a neuromuscular synapse. What would result from such a block? (see figure 3) the loss of ability to contract the muscle The muscle would become permanently contracted. The muscle would remain fixed at the length it was when the toxin contacted it.

the loss of ability to contract the muscle

Which of the following regions best identifies where myosin would have maximum cross-bridge access to actin? (see figure 2) the region between 3 and 5 the region between 1 and 2 the region between 2 and 3 4

the region between 2 and 3

recruitment

the more motor units contracting, the faster and more prolonged the contraction

Eccentric Contractions

the muscle generates force as it lengthens; are important for coordination and purposeful movements; occur in calf muscle for example; 50% more forceful then concentric

Based on what you know of the relationship between the thick and the thin filaments, what would happen if a disorder existed that caused a person to produce no tropomyosin?

the muscles would never be able to relax

Motor Unit

the nerve-muscle functional unit; consists of a motor neuron and all the muscle fibers it supplies; small motor units (more precise movement) [ex: fingers], larger motor units (less precise movement) [ex: hip muscles, bone]

Load

the opposing force exerted on the muscle by the weight of the object to be moved

Anaerobic Threshold

the point at which muscle metabolism converts to anaerobic glycolysis

The contractile, or functional, unit of a muscle fiber is __________.

the sacromere

The contractile, or functional, unit of a muscle fiber is

the sarcomere

The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________.

the site of calcium regulation differs

Muscle Fatigue

the state of physiological inability to contract even though the muscle still may be receiving stimuli; due to a problem in excitation-contraction coupling or, in rare cases, problems at the neuromuscular junction

Threshold Stimulus

the stimulus at which the first observable contraction occurs

Maximal Stimulus

the strongest stimulus that produces increased contractile force; represent the point at which all the muscles motor units are recruited

What is the main factor that determines the power of a muscle?

the total number of muscle cells available for contraction

Which of these is NOT a way of classifying muscles?

the type of muscle fibers

Smooth muscle is characterized by all of the following except ________.

there are more thick filaments than thin filaments

Contains ATPases

thick

Contains myosin

thick

Does not lie in the I band

thick

thick (myosin) filaments

Attaches to the z disc

thin

Contains troponin

thin

contains actin

thin fillament

Concentric Contractions

those in which the muscle shortens and does work, such as picking up a book or kicking a ball;

Latent period

time following muscle stimulation, but before contraction occurs

An enzyme known as acetylcholinesterase is present in the synaptic cleft. What is its role? (see figure 3) to facilitate the entrance of acetylcholine into the muscle cell to pump Ca2+ back out of the axon terminal to facilitated transport of acetylcholine across the cleft to break down acetylcholine

to break down acetylcholine

The function of T tubules in muscle contraction is to

transmit the action potential deep into the muscle cells

Excitation-Contraction Coupling (2)

traveling down of action potential causes t tubule voltage sensitive protein to change shape; opens a calcium release channel in SR allowing calcium ions to flee sarcplasm; this rapid influx of calcium triggers contraction of muscle fibers

The phenomenon in which the contraction strength of a muscle increases, due to increased Ca2+ availability and enzyme efficiency during the warm-up.

treppe

Muscle cells store more creatine phosphate than ATP resulting in the muscle having a reserve source of energy.

true

Peristalsis is characteristic of smooth muscle.

true

Which type of muscle is found in the wall of hollow organs?

unitary smooth muscle

Glycogen Anearobic Pathway

used when their is not enought glucose; stored fat; Yields 3 ATPs because it has allready been partially hydrated; also yields 2 pyruvic acids

The situation in which contractions become stronger due to stimulation before complete relaxation occurs.

wave summation

Myasthenia gravis is a disease that is believed to be caused by autoimmune disorder, resulting in the loss of ACh receptors at the motor end plate of muscle fibers. Which of the following is likely to be a symptom of myasthenia gravis?

weakness of muscle

direct phosphorylation

weight lifting

Glucose Anearobic Pathway

yields 2 ATPs; does not require oxygen; also yeilds 2 pyruvic acids

Aerobic Pathway

yields the most ATP with Oxygen; needs pyruvic acid to be shuttled from mitochondria (it is shuttled from Anearobic Pathway when 2 ATP and 2 Pyruvic acids); Pyruvic acid is transformed to Acetylcoa (happens in cytoplasm of cell); Krebs cycle produces 32 ATP

Muscles + Muscle Tissue (Ch. 9)

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