BIO 201- CH 9 Lecture

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What are the characteristics of skeletal muscle?

- attach and cover the bony skeleton - has striations (obvious stripes) - only muscle tissue under voluntary control - responsible for overall body motility - contracts rapidly, tires easily

What are the four special characteristics that help muscle tissues perform their duties?

- excitability - contractility - extensibility - elasticity

What are characteristics of cardiac muscles?

- forms the walls of the heart - is striated - is involuntary - contracts at steady rate set by heart's pacemaker - contractions can speed up in response to bodily needs

What are the characteristics of Smooth muscle?

- found in the walls of hollow visceral organs - is not striated - is involuntary muscle - forces food and other substances through internal body channels - produces slow, sustained contractions

What are the muscle's four basic important functions that they perform?

- movement - maintaining body posture - stabilizing joints - generating heat

What are the two functions of the sarcoplasmic reticulum?

- regulate intracellular levels of Ca - forms terminal cisternae at the A band-I band junction

What skeletal muscle structures can be seen without a microscope?

- skeletal muscle tissue - blood vessels - nerve fibers - connective tissue - attachments

At resting potential, the inside of the sarcolemma is negative at _____mv.

-70 mv

What are the three major connective tissue sheaths?

-epimysium -perimysium -endomysium

What are the three different types of muscle tissue?

1. Skeletal 2. Cardiac 3. Smooth

What are the steps of activation of a muscle fiber cell?

1. action potential in axon arrives at axon terminal 2. Ca^2+ enters the axon 3. synaptic vesicles fuse with the axonal membrane 4. ACh is released into the synaptic cleft 5. ACh diffuses across the synaptic cleft 6. ACh binds to receptor proteins 7. ACh is broken down

What are the steps of contraction?

1. action potential reaches T-tubules 2. terminal cisternae release Ca^2+ 3. Ca^2+ binds to troponin 4. contraction occurs across cross bridges 5. removal of Ca^2+ 6. tropomyosin restored

What are the three steps involved in inducing a skeletal muscle cell to contract?

1. activation 2. propagation of an action potential 3. increase in intracellular Ca^2+ levels

What are the steps to anaerobic glycolysis?

1. bulging muscles compress the blood vessels within them 2. blood flow and oxygen delivery is impaired 3. oxygen deficit results 4. pyruvic acid is converted to lactic acid 5. this produces only 2 ATPs/glucose but it works without oxygen

What two ways are muscle responses graded?

1. changing the frequency of stimulation 2. changing the strength of stimulation

What are the four steps of the cross bridge cycle?

1. cross bridge formation 2. power stroke 3. cross-bridge detachment 4. cocking of the myosin head

What are the three phases to a muscle twitch?

1. latent period 2. period of contraction 3. period of relaxation

Overview of the Contraction of Skeletal Muscle

1. nerve impulses reach the axon terminal 2. Ca2+ channels open 3. synaptic vesicles fuse w/axonal membrane 4. ACh is released 5. ACh diffuses 6. ACh binds 7. Na+ channels open causing the motor end plate to depolarize 8. Ca2+ is released 9. Ca2+ causes troponin/tropomyosin to move from active site 10.myosin head creates a cross bridge 11.ACh is destroyed 12.sarcolemma is repolarized 13.Ca2+ is removed from the muscle fiber

What are the five steps of the propagation of an action potential?

1. resting potential 2. depolarization 3. action potential 4. repolarization 5. Na/K pump

What are unique characteristics of smooth muscle fibers?

1. spindle-shaped 2. uninucleate 3. much smaller than skeletal muscles 4. lack coarse connective tissue sheaths

Contractions can increase due to two factors, what are these factors?

1.increased availability of Ca2+ in the sarcoplasm 2.muscle enzymes become more efficient because heat is increased as the muscles contract

The diameter of a skeletal muscle fiber is ____ to ____ um (10x an average body cell).

10 to 100

The Creatine Phosphate (CP) is used up in less than ____.

20 seconds

The length of a skeletal muscle fiber is up to ______cm.

30

women's skeletal muscle makes up ___% of their body mass. While men's make up ___% of their body mass. Why?

36% / 42% because of testosterone

During aerobic respiration, one glucose molecule makes ____ ATP molecules.

36-38

Muscles only store about ____ seconds of reserve of ATP

4-6 seconds

By age 80, ___% of muscle mass is lost.

50%

When muscles contract vigorously and contractile activity reaches about ____% of maximum anaerobic glycolysis will occur.

70%

During rest and light to moderate exercise, ___% of ATP used is supplied by aerobic respiration.

95%

bands of both thin and thick filaments in a myofibril

A band

During depolarization of propagation of an action potential, what causes the sodium channels to open?

ACh from the axon

As we begin to exercise, the demand for ____ soars.

ATP

_____ is the only source of energy used directly for contractile activity

ATP

How is each muscle fiber produced?

By the fusion of hundreds of embryonic cells.

Short activities such as sprinting or weight lifting require a surge of power and rely on ____ stores in the muscle.

CP and ATP

a lighter region in the midsection of the A band that is made up of only thick filaments

H zone

bands of only thin filaments in a myofibril

I band

How do muscle tissues differ?

In structure, location, function, and means of activation

Muscles can attach two different ways. Which way is more common?

Indirect attachment because of its durability and small size.

Muscle that cannot ordinarily be consciously controlled

Involuntary muscle

a dark band of proteins that bisects the H zone and anchors thick filaments

M line

During the resting potential of propagation of an action potential, the sarcolemma is relatively impermeable to ___ and ____.

Na and K

The ionic concentration of the resting state is restored by the ____. What step is this in propagation of an action potential?

Na/K pump. the last step

During depolarization, ___ enters the cell, causing the inside to become more positive.

Na^+

Once initiated, can the action potential be stopped?

No

A type of muscle tissue composed of cylindrical, multinucleate cells with obvious striations that forms the major muscles of the body

Skeletal muscle

How does the function movement affect each type of muscle: skeletal, cardiac, and smooth?

Skeletal- locomotion and manipulation Cardiac- movement of blood Smooth- movement through hollow organs

A type of muscle tissue composed of nonstriated, uninucleate cells found mainly in the walls of hollow organs

Smooth muscle

What conducts impulses to the deepest regions of the muscle?

T tubules

What greatly increases the muscle cell's surface area?

T tubules

extension of the sarcolemma in muscle cells that protrudes deeply into the muscle cell

T tubules

Muscle that is under strict, conscious nervous control

Voluntary muscle

protein disk that anchors thin filaments and divides two sarcomeres in a myofibril

Z disc

What is an example of complete tetanus?

a person lifting a car off of another person

What is the appearance of a myosin molecule?

a rod-like tail and two globular heads made of polypeptides

How many myosin molecules do each thick filament contain?

about 300 myosin molecules

At the neuromuscular junction, the synaptic vesicles release the neurotransmitter _____ into the ______.

acetylcholine (ACh) into the synaptic cleft

What are thin filaments composed of?

actin

a depolarization event that is conducted along the membrane of a muscle cell or nerve fiber that creates an electrical current

action potential

organic molecule that stores and releases chemical energy for use in the body cells of all living things

adenosine triphosphate (ATP)

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

aerobic endurance

During rest and light to moderate exercise, 95% of ATP used is supplied by _____.

aerobic respiration

Prolonged activities where endurance not power is the goal such as a marathon or jogging depend mostly on ____.

aerobic respiration

The most efficient respiration process is the ____.

aerobic respiration

respiration in which oxygen is consumed and glucose is broken down entirely to produce water, carbon dioxide, and large amounts of ATP, also call cellular respiration

aerobic respiration

embryonic growth factor that stimulates the clustering of acetylcholine receptors at the motor end plate

agrin

What is propagation of an action potential as related to the steps of inducing a skeletal muscle to contract?

an electrical current is generated along its sarcolemma

When muscles contract vigorously and contractile activity reaches about 70% of maximum ___ will occur.

anaerobic glycolysis

conversion of glucose to lactic acid to produce ATP when sufficient oxygen is not available to perform aerobic respiration

anaerobic glycolysis

On and off activities that require periodic bursts of activity such as soccer and tennis are mostly fueled by ____.

anaerobic respiration

the point at which muscle metabolism converts to anaerobic glycolysis

anaerobic threshold

Where do T tubules occur?

at the A band-I band junction

Where does activation occur?

at the neuromuscular junction

During activation, axons of the motor neurons enter muscles and _____.

branch profusely

When does sarcopenia begin?

by age 30

A type of muscle tissue composed of branching cells that are generally uninucleate that forms the walls of the heart

cardiac muscle

pouch-like infoldings in the sarcolemma of smooth muscle fibers that act as calcium ion reservoirs

caveolae

During action potential, what causes Na channels of an adjacent patch of sarcolemma to open?

charge reversal of the initial patch of sarcolemma

deep layer of smooth muscle fibers that run around the organ

circular layer

a situation in which all evidence of muscle relaxation disappears and the muscle contraction fuses into a smooth sustained contraction plateau

complete tetanus

Individual muscle fibers are wrapped and held together by ___________.

connectie tissue sheaths

the ability to move by shortening forcibly

contractility

During the _____, thin filaments slide past thick ones so that the actin and myosin filaments overlap to a greater degree.

contraction

ADP + creatine phosphate = ____

creatine + ATP

organic high-energy molecule stored in muscles that is tapped to regenerate ATP

creatine phosphate (CP)

the sequence of cyclical events in which myosin heads on a thick filament attach to the actin on thin filaments and pull them towards the M line

cross bridge cycle

The globular heads of myosin molecules attach to the active sites of the actin subunits to form _____.

cross bridges

What acts as motors to generate the tension developed during muscle contraction?

cross bridges

the area where an axon delivers an impulse to a smooth muscle fiber made up of a varicosity, wide synaptic cleft, and the smooth muscle fiber

diffuse junction

epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage

direct attachment

What are the two different ways that muscles can attach?

direct attachment and indirect attachment

What component of thick filaments allow the filament to spring back into shape after being stretched?

elastic filaments

the ability of a muscle cell to recoil and resume its resting length after being stretched

elasticity

sheath of fine areolar connectie tissue that surrounds each individual muscle fiber

endomysium

sheath of dense irregular connective tissue that surrounds the whole muscle

epimysium

the ability to receive and respond to stimuli

excitability

Propagation of an action potential and increase in intracellular Ca levels (steps 2 and 3 in muscle contraction) are called ______.

excitation-contraction coupling

the sequence of events by which the transmission of an action potential along the sarcolemma leads to the sliding of myofilaments

excitation-contraction coupling

the ability to be stretched or extended

extensibility

bundle of nerve or muscle fibers bound together by connective tissue

fascicle

What do T tubules impulses signal?

for the release of Ca^2+ from the adjacent terminal cisternae

granule of stored glycogen that provide glucose during periods of muscle cell activity

glycosome

Sarcoplasm is similar to that of other cells but has unusually large amounts of ____ and ______.

glycosomes and myoglobin

variations in the degree of muscle contraction by changing either the frequency or strength of the stimulus

graded muscle response

Skeletal muscles fiber are _______ cells.

huge

a situation in which a muscle contraction is sustained but quivering

incomplete tetanus

What is the final trigger for contraction?

increase in intracellular Ca^2+ levels

Muscle's connective tissue wrappings extend beyond the muscle as a tendon or aponeurosis connecting to bone, cartilage, or other muscle

indirect attachment

attachment of a skeletal muscle to a bone that moves during muscular contraction

insertion

contraction of a muscle in which the muscle does not shorten but its internal muscle tension increases

isometric contraction

What are the two types of muscle contraction?

isometric contraction and isotonic contraction

contraction of a muscle in which muscle tension remains constant at a given joint angle and load, and the muscle shortens

isotonic contraction

Large, weight bearing muscles (hips, thighs) with less precise movements have ____.

large motor units

period of time between stimulation and the onset of muscle contraction, during which excitation-contraction coupling is taking place

latent period

What is an example of isotonic contraction?

lifting a 10 lb. book

Which layer of the smooth muscle fiber is responsible for shortening and dilating of the organ?

longitudinal layer

superficial layer of smooth muscle fibers that run along the long axis of the organ

longitudinal layer

What are the two sheets of fibers at right angles to each other that smooth muscle fiber is organized into?

longitudinal layer and circular layer

the strongest stimulus that increases contractile force

maximal stimulus

At the neuromuscular junction, the sarcolemma forms the ______.

motor end plate

highly folded portion of the sarcolemma that contains ACh receptors

motor end plate

a motor neuron and all of the muscle cells it stimulates

motor unit

a state of physiological inability to contract in which a muscle's tension drops to zero

muscle fatigue

A skeletral or smooth muscle cell

muscle fiber

the force exerted by a contracting muscle on some object

muscle tension

What makes up nearly half of the body's mass?

muscle tissue

What is very important to joint stability?

muscle tone

If only a single stimulus occurs, ____ will result.

muscle twitch

the response of a muscle to a single, brief threshold stimulus

muscle twitch

What are the three prefixes that refer to muscle?

myo- mys- sarco-

embryonic mesoderm cells from which all muscle cells develop

myoblasts

rod-like bundle of contractile filaments (myofilaments) found in muscle fibers

myofibril

What accounts for about 80% of the cell's volume?

myofibrils

filaments of actin or myosin that form myofibrils

myofilament

a red protein found in muscle fibers that stores oxygen

myoglobin

What are thick filaments composed of?

myosin

During activation, each set of axonal branches forms a __________ with a single muscle fiber.

neuromuscular junction

region made up of the axon terminals, synaptic clefts, and motor end plates where a motor neuron comes into close contact with a skeletal muscle

neuromuscular junction

Are muscle twitches the way our muscles normally operate?

no

attachment of a skeletal muscle to a bone that remains relatively fixed during muscular contraction

origin

What are the two places that most skeletal muscles span joints and are attached to bone or structures?

origin and insertion

idea that forcing a muscle to work hard promotes increased muscle strength and endurance

overload principle

As long as a muscle cell has enough ____, it will form ATP by the aerobic pathway.

oxygen

sheath of fibrous connective tissue that bundles muscle fibers into fascicles

perimysium

period of time during which cross bridges form, muscle tension increases, and the muscle shortens

period of contraction

period of time during which Ca2+ is reabsorbed into the sarcoplasmic reticulum and the muscle tension decreases to zero

period of relaxation

The force of a contraction is controlled by _____ or multiple motor unit summation.

recruitment

_____ occurs from threshold stimulus to maximal stimulus.

recruitment

the phenomenon by which more and more motor units are incorporated into a muscle contraction as stimuli increase

recruitment

During the _____, thin and thick filaments overlap only slightly.

relaxed state

During what step of propagation of an action potential does K diffuse from the cell, restoring electrical polarity (resting potential) of the sarcolemma?

repolarization

What must occur before the muscle can be stimulated again?

repolarization

At the neuromuscular junction, as ACh is released from the axon, it travels to the ______ of the muscle fiber.

sarcolemma

At the neuromuscular junction, the _____ forms the motor end plate.

sarcolemma

the plasma membrane of a muscle fiber

sarcolemma

the smallest contractile unit of a muscle that consists of the region between two successive Z discs on a myofibril

sarcomere

the gradual loss of muscle mass that occurs with aging

sarcopenia

the cytoplasm of a muscle fiber

sarcoplasm

specialized smooth endoplasmic reticulum that surrounds each myofibril in muscle cells

sarcoplasmic reticulum

Skeletal muscles contain what two sets of intracellular tubules that participate in the regulation of muscle contraction?

sarcoplasmic reticulum and T tubules

When muscles contract, the sarcomeres ____.

shorten

smooth muscle contraction is similar to _____.

skeletal muscle contraction

Each _______ is a long cylindrical cell with multiple oval nuclei just beneath the sarcolemma.

skeletal muscle fiber

model that states that during muscle contraction, the thin filaments slide past the thick filaments so as to increase their degree of overlap

sliding filament model of contraction

Muscles that control fine movements (fingers, eyes) have _____.

small motor units

Unlike skeletal muscle, _____ muscle relies heavily on extracellular Ca2+ to trigger muscular contractions.

smooth

T tubules are notably absent from _____.

smooth muscle

Thick and thin filaments are arranged diagonally in ____.

smooth muscle

____ has no sarcomeres.

smooth muscle

____ lacks a structured neuromuscular junction

smooth muscle

nerve cells of the somatic (voluntary) nervous system

somatic motor neuron

Skeletal muscles are simulated (activated) by ______.

somatic motor neurons

Muscle fibers in a single motor unit are _____.

spread throughout the muscle

increased contraction in response to multiple stimuli of the same strength

staircase response

Within the steps of inducing a skeletal muscle cell to contract, how does activation occur?

stimulation by a nerve cell

gel-filled space between an axon terminal and the neuron or body cell it communicates with

synaptic cleft

At the neuromuscular junction, axon terminals contain many _____.

synaptic vesicles

small membranous sacs that contain a neurotransmitter to be released from a neuron by exocytosis

synaptic vesicles

What gives the muscles their striated appearance?

the A bands and I bands

What happens when muscles contract?

the insertion moves toward the origin

What are thin filaments composed of?

the protein actin

What are thick filaments composed of?

the protein myosin

What is the final trigger for muscle contraction?

the release of Ca^2+ ions by the terminal cisternae

Body strength per unit of muscle mass is _____ in both sexes.

the same

What are the two types of myofilament?

thick filaments and thin filaments

________ contain the active sites to which the myosin heads attach during contraction.

thin filaments

the weakest stimulus capable of producing an observable contraction

threshold stimulus

What is the primary function of wave stimulus?

to produce smooth, continuous muscle contractions

T tubules and their associated paired terminal cisternae form a ____.

triad

a successive grouping of terminal cisternae-T tubule-terminal cisternae that occurs between two sarcomeres

triad

Thin filaments also contain the proteins ______ and ______ that help control the myosin-actin interactions.

tropomyosin and troponin

What is an example of isometric contraction?

trying to lift a 2000 lb. car

a knob-like swelling of autonomic axons that contain mitochondria and synaptic vesicles

varicosity

phenomenon where rapid firing of neurons results in and summative effect in which successive muscle twitches grow stronger

wave stimulation

Stimulation of a single motor unit causes a ___ contraction of the entire muscle.

weak

sarcomeres are present and muscles are contracting by ___ of development in all muscle types.

week 7

When do muscles generate heat?

when they contract


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