muscle tissue chapter 10

Describe resistance training

- "Strength training" - moderate increase in the frequency of motor unit activation and a large increase in force production - fewer repetitions w/ heavier weight. - use of free weights or resistance - exercise machine

Describe peristalsis

- Circular and longitudinal layers produce rhythmic waves (contract and relax) - propels materials through hollow organs of digestive, urinary and reproductive systems

What are 2 potential sources of glucose for glycolysis?

- Glucose that enters the fibers from the bloodstream -storage form of glucose called glycogen.

Describe an isotonic eccentric contraction (plyometric)

- Greatest amount of tension and force - Muscle lengthening - force generated by the muscle is less than that of the external load (greater injuries)

What are the 3 MAIN ways smooth muscle differs from skeletal muscle?

- It lacks motor end plate - The SR is much less extensive - T- tubules are absent

Describe the structure of smooth muscle cells

- Lack striation and sarcomeres - HAS DENSE BODIES - thin < thick filaments - thin filaments lack troponin

What is the "latch state" during the relaxation state for smooth muscles?

- Maintains tension while consuming very little ATP - Maintains a state of energy efficient sustained contraction (sphincters)

What are the stimulations for smooth muscle contractions?

- Mechanical stimulation (stretch) - Hormonal stimulation - Nervous system stimulation

Describe multi-unit smooth muscle

- RARE - found in uterus, muscles in the eyes, arrector pili muscles - consists of individual muscle cells NOT joined by gap junctions - each cell contracts independently, permitting precise control of contractions

Describe how a smooth muscle cell turns into the relaxation state in relation to CALCIUM

- Removal of calcium ions from cytosol - Calcium ions dissociate from calmodulin - MLCK is inactivated - Enters latch state

What are the 2 types of smooth muscle?

- Single-unit (unitary) smooth muscle or visceral smooth muscle - Multi-unit smooth muscle

Describe the Length-Tension Relationship

- The # of crossbridges depends on the length of the sarcomere prior to contraction.

How can pacemaker cells depolarize and contract spontaneously?

- They have unstable membrane potentials that cause them to spontaneously depolarize - They are responsible for the waves of contraction.

What are some types of Type II fibers?

- Type IIa --> fast oxidative glycolytic (FOG) - Type IIx --> fast oxidative (FO) - Type IIb --> fast glycolytic (FG)

What are some of the factors of muscular fatigue?

- depletion of key metabolites --> Creatine Phosphate, glycogen, blood glucose - decreased availability of O2 to muscle fibers - accumulation of certain chemicals --> calcium ions accumulate in mitochondria - environmental conditions --> extreme heat

Type II fibers

- fast-twitch fibers - contract more rapidly - quickly fatigued - rely on glycolytic energy sources - less myoglobin - fewer mitochondria - less extensive blood supply - "white" meat of the chicken

What are the classes of skeletal muscle fibers?

- fast-twitch fibers - slow-twitch fibers

To return to homeostasis, the body must:

- heat dissipation - restoration of intracellular and a extracellular ion concentration - correction of blood pH - ALL OF THESE PROCESSES CONSUME ATP

What are the functions of muscle tone?

- maintaining erect posture - stabilizing joints - generating heat - ensuring that the muscle is ready to respond if movement is initiated

What are the function of smooth muscle?

- peristalsis - formation of sphincters - regulation of flow

Describe Single-Unit (unitary) smooth muscle or visceral smooth muscle

- predominant type - found in nearly ALL hollow organs - consists of 100-1000s of muscle cells whose plasma membranes are linked electrically via GAP JUNCTIONS, causing the muscle cells to contract in a coordinated wave and as a single unit - Has multiple types of stimulation

Describe the smooth muscle function of formation of sphincters

- rings in both digestive and urinary system - usually contracted but relax periodically to allow substances to pass through them

Describe Type I fibers

- slow-twitch fibers - contract slowly; less forcefully - requires the continual oxidative generation of large quantities of ATP - large quantities of myoglobin - many mitochondria - well-developed bloody supply - slow oxidative fibers - "dark meat" of chicken

Describe Cardiac Muscle

- striated - consists of sarcomeres - have BOTH T- tubules and SR - shorter, branched cells - one or two nuclei - abundant myoglobin - mitochondria is about 30% of cytoplasmic vol - has INTERCALATED DISCS - electrical activity is coordinated by PACEMAKER CELLS

What value best represents resting membrane potential of skeletal muscle cells?

-85 mV

What is the resting membrane potential?

-85 mV. The cytosol is about 85 mV more negative than the extracellular fluid.

What causes spasms to occur?

-dehydration -electrolyte imbalances -muscle injury -muscle overload

Describe the steps of the oxidative energy source

-electrons are removed from carbon-based molecules and the energy liberates is then used to fuel synthesis of ATP -final step: transfer of electrons to a moleculre of O2 (which is why it can also be called aerobic catabolism)

What are the immediate sources of energy for muscle contraction?

-immediate energy sourse for contractin of the muscle fiber --> ATP - Creatine Phosphate (CP): a molecule used in a reaction to regenerate ATP immediately - Creatine Phosphate reaction: ADP + Creatine Phosphate --> ATP + creatine (10 secs of maximal muscle activity i.e. 100- meter sprint.)

axon terminal or synaptic bulb

...

skeletal muscle mitochondria

...

Name and describe the 4 steps of the crossbridge cycle

1. ATP hydrolysis "cocks" the myosin head 2. The myosin head binds to actin. 3. The power stroke occurs when the ADP and phosphate detach from the myosin head; myosin pulls actin toweard the center of the sarcomere. 4. ATP breaks the attachment of myosin to actin

Describe the steps of Muscle Relaxation

1. AchE degrades the remaining Ach, and the final repolarization occurs ----> ligand-gated ions channels in teh motor end plate close. 2. The sarcolemma returns to its resting membrane potential, and calcium ion channels in the SR close 3. Calcium ions are pumped back into the SR, returning the calcium ions concentration in the cytosol to its resting level (active transport pumps in SR consume ATP to pump calcium ions) 4. Troponin and the tropomyosin block the active sites of actin, and the muscle relaxes (with support from titin and other structural proteins, myofilaments then slide back into their original positions)

Calcium ions initiate:

1. Calcium ions bind to a protein in the sarcoplasm called calmodulin. 2. The calcium ion-cam complex activates an enzyme associated w/ myosin --> myosin light-chaine kinase (MLCK). e. MLCK causes the activatoin of myosin ATPase 4. Crossbridge cycles then ensue.

Describe the steps of the Contraction Phase: The cross bridge cycle of the Sliding-Filament Mechanism

1. Calcium ions bind to troponin 2. Tropomyosin moves, and the active sites of actin are exposed

How many components are there for muscle relaxation? Describe each component.

2 components. 1. ACh release stops and the remaining ACh in the synaptic cleft is broken down 2. Calcium ion concentration in the cytosol returns to its resting level.

What is the product of glycolysis and describe what it does w/ O2 and when there is no O2

2 molecules of pyruvate. w/O2: Enters the mitochondria for oxidative catabolism. w/o O2: Converted to 2 molecules of lactic acid (lactate). Less than 20% of the lactate is converted to glucose by the the liver.

What does a triad consist of?

2 terminal cisternae and 1 T-Tubule

How many times does the process of ATP breaking the attachment of myosin to actin occur for each myosin head in each sarcomere of the muscle fiber

20-40 times for each myosin head in each sarcomere of the muscle fiber

What do the postural muscles of the back or the gastrocnemius in call contain? (in regards to how many fibers per motor unit)

2000-3000 muscle fibers in each motor unit. NOT as precise.

How many subunits does troponin have and name the function of each

3 subunints. One binds to calcium ions, one binds to actin, and one binds to tropomyosin

How long does a muscle twitch last?

5 ms.

What is the dark area that has both thick and thin filament?

A band

Define atrophy

A condition in response to physical inactivity the diameter of the muscle fiber decreases due to loss of myofibrils.

Define voltage

A difference in electrical potential between 2 points (measured in volts)

Actin

A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.

Troponin

A globular protein that ssociated with tropomyosin as part of the thin filament of the sarcomere. Troponin binds Ca2+, which causes the conformaiton change in tropomyosin required to expose the myosin-binding sites on actin and initiate muscle contraction.

Tropomyosin

A helical protein that winds around actin helices in skeletal and cardiac muscle cells to form the thin filament of the sarcomere. In the absence of Ca2+, tropomyosin covers the myosin-binding sites on actin and prevents muscle contraction. When calcium is present, a conformation change in tropomyosin occurs so that the myosin-binding sites are exposed and muscle contraction can occur.

axon

A long, thin fiber that transmits signals away from the neuron cell body to other neurons, or to muscles or glands

What is the Principle of Myoplaticity?

A muscle will alter its structure to follow its function

What is a "cross bridge"

A myosin head bounds to an actin

Define hypotonia

A nervous system disorder that makes the tone in skeletal muscle abnormally low. - looks flattened, feels soft and loose - joints are hyperextended

Describe the neuromuscular junction

A neuromuscular junction is the connection between the motor neuron and muscle fiber. Here the muscle fiber membrane is specialized to for a motor end plate. In this region of the muscle fiber, nuclei and mitochondria are abundant and the cell membrane is extensively folded.

What is the recovery period?

A period of time to return to the pre-exercise state

Myosin

A protein present in muscle fibers that aids in contraction and makes up the majority of muscle fiber

What does a motor unit consist of?

A single motor neuron along w/ the muscle fibers it innervates

Describe what a motor neuron does in relation to muscles

A single neuron communicates w/ many muscle fibers. The connection is called a synapse.

What is a contraction?

A succession of crossbridge cycle and the resulting production of force

Describe the structure and function of a tendon

A tendon is a fibrous band or cord of white connective tissue at the ends of muscle fibers that serves to attach a muscle to a bone and other structure. Tendons are strong and flexible but inelastic.

Myofibril

A threadlike structure, extending longitudinally through a muscle fiber (cell) consisting mainly of think filaments (myosin) and thin filaments (actin, troponin, and tropomyosin)

Complete the reaction below: ADP + creatine phosphate → creatine + __________

ATP

What are possible products of glycolytic, or anaerobic, catabolism?

ATP, pyruvate, and lactic acid

Which molecule has an active site to which myosin heads bind?

Actin

What are thin filaments made up of?

Actin (active site), tropomyosin (covers active site), and troponin (holds tropomyosin in place.

What are dense bodies?

Actin filaments are arranged obliquely in the sarcoplasm and are anchored to proteins

Describe conductivity in relation to muscle cells

Allows electrical changes to spread (action potential propagation)

Describe extensibility in relation to muscle cells

Allows muscles to be stretched without damage

What is a myogram?

An instrument that records the twitch and generates a recording

Describe electrically excitable cells

An unequal distribution of electrically charged ions near the plasma membranes of the cells

H zone(s)

Are areas in the center of the A bands containing only thick filaments Contain myosin only Zones shrink during contraction

Describe "Recruitment"

As greater force is needed, more motor units are activated (slow motor units and if needed, fast motor units are "recruited")

What does the NMJ consist of?

Axon terminal, synaptic cleft, and motor end plate.

endomysium

Connective tissue surrounding a muscle fiber

Describe the intercalated discs of cardiac muscle

Connects cardiac muscle cells and contains desmosomes and gap junctions. Helps the heart contract as a UNIT

What does the larynx or fingers contain? (in regards to how many fibers per motor unit)

Contains as few as 10 muscle fibers per unit. Allows more PRECISE control over the amount and rate of tension produced.

What do myofilaments consist of?

Contractile proteins (produces tension), regulatory proteins (control contractions) , and structural proteins (holds myofilaments in place and ensures structural stability of the myofibril and muscle fiber.)

What are the 5 common properties of muscle cells

Contractility, Excitability, Conductivity, Extensibility, and Elasticity.

What is the M line? What does it consist of?

Dark line in the A bands. Consists of structural proteins that hold the thick filaments in place and serve as an anchoring point for the elastic filaments.

What is the Z-disc? What does is consist of?

Dark line in the I bands. It is composed of structural proteins that: anchor the thin filaments in place and to another. Is the attachment point for elastic filaments. It attaches myofibrils to one another across the whole diameter of the muscle fiber.

What does amitotic mean?

Does not undergo mitosis. These are mature skeletal muscle fiber nuclei.

Define membrane potential

Electrical potential across its plasma membrane.

Define the resting membrane potential

Electrical potential across the sarcolemma in a muscle fiber @ rest Membrane is considered to polarized during the resting phase because two sides of opposite charges are present (ex. magnet)

What are the 2 types of training?

Endurance training and resistance training

What is the terminal cisternae?

Enlarged portions of the SR

Identify and describe the 3 connective tissue layers associated with a skeletal muscle

Epimysium perimysium and endomysium

What are the 3 parts of process of muscle contraction

Excitation phase, Excitation-contraction coupling, and the Contraction phase

Describe isometric contraction

External load is equal to the force generated by the muscle. SAME LENGTH, CHANGING TENSION

What type of motor units does Type II muscle fibers contain?

Fast motor units

What are slow-twitch fibers? Give an example of one.

Fibers w/ low myosin ATPase activity (ex. postural muscles of the back)

Transverse (T) tubule

Folds of Sarcolemma that fold inwards across the muscle fibre and stick into the Sarcoplasm. These aid in spreading electrical impulses

Where is Creatine Phosphate found in?

Found in muscle fibers; 5-6 times more abundant than ATP in cytosol

Describe elasticity in relation to muscle cells

Give the ability to return to original shape after stretching.

Describe glycolysis in relation to muscles.

Glycolysis is a series of rxns that takes place in cytosol of all cells (30-40 secs of sustained muscle contraction). -Glucose is broken down to produce 2 ATP per molecule of glucose.

what is the area within that only has thick filaments

H zone

Are smooth and cardiac muscles voluntary or involuntary?

Involuntary

What are the types of general muscle contractions?

Isotonic contraction and isometric contraction.

What does the myosin head contain?

It contains: a site that binds to ATP, a site that binds to ATPase enzyme that hydrolyzes ATP to an ADP and a P (phosphate group) <-- ADP and P remains attached when "cocked"

Describe the Excitation phase

It involves transmission of a signal fro mthe motor neuron --> sarcolemma of a muscle fiber

What does AchE stand for and what does it do?

It is Acetylcholinesterase. It is an enzyme in the synaptic cleft that immediately degrades and inactivates ACh.

Why do action potentials happen?

It is for long-distance signaling. Action potentials don't stay in one place; rather, they are conducted, or propagated throughout the entire sarcolemma (ex. ripples in a pond)

Describe the depolarization stage

It is in response to a stimulus, voltage-gated sodium ions enters cell (membrane potential --> less negative) --> +30 mV.

Describe the motor end plate

It is the folded surface and contains many receptors (ligand-gated ion channels) for Ach (ligand)

What is the sarcolemma and what is it composed of?

It is the plasma membrane of the muscle cell. Composed of: phospholipid bilayer w/ multiple specialized integral and peripheral proteins.

Why do skeletal muscle fibers have multiple nuclei?

It is the result of embryonic origin of fiber, as each muscle fiber arises from the fusion of multiple embryonic cells (myoblasts)

what does the "cross bridge cycle" lead to?

It leads to a sliding of myofilaments

Where does "maximal tension production" occur?

It occurs in a narrow range of resting sarcomere lengths, near the optimal length of the sarcomere.

What is the endomysium?

It surrounds the extracellular matrix and holds the muscle cells together within muscle tissue

What happens to tension when a sarcomere is overly shortened or overly stretched?

Less tension will be produced.

What are the 2 types of gated channels?

Ligand-gated channels and volage-gated channels.

I band(s)

Light bands containing thin filaments only and extend from the A Band of one sarcomere to the A Band of the next sarcomere.

Skeletal muscle tissue is made up of:

Long, multinucleated muscle cells that are arranged parallel to one another. Attached by connective tissue to the skeleton. They are voluntary.

What is the protein line that stabilize and support thick filament?

M line

M Line

Middle of sarcomere, holds thick filament in place

M line

Middle of sarcomere, holds thick filament in place midline of myosin fibers

Describe the sarcoplasmic reticulum (SR)

Modified smooth ER. Forms a weblike network surrounding each myofibril

What types of fiber classes do most muscles contain?

Most muscles contain ALL fiber classes, each of which is stimulated under different conditions

skeletal muscle nucleus

Multiple nuclei in one cell (multinucleate) Dark structure inside endomysium

Latrotoxin, produced by the poisonous black widow spider, increases the release of acetylcholine. How do muscle cells respond?

Muscle cells will experience fused or complete tetanus when excess acetylcholine exists.

What are fast-twitch fibers? Give an example of one.

Muscle fibers w/ high myosin ATPase activity, they proceed rapidly through contraction cycles (ex. eyeballs)

Muscle tissues consists of:

Myocytes

Which statement best describes the function of myoglobin?

Myoglobin stores oxygen in muscle cells.

The molecule on which ATPase (enzyme that breaks down ATP into ADP) is found.

Myosin

What do thick filaments contain?

Myosin

What energy source is used for longer-lasting muscle activity?

Oxidative energy sources.

What are smooth muscle cells that are able to depolarize and contract spontaneously called?

Pacemaker cells

Describe Excess Postexercise O2 Consumption (EPOC)

Persisting increased rate of breathing

What causes a change in skeletal muscle performance?

Physical training

Describe isotonic contraction

Produces enough tension to initially move a load, such as a weight, and then maintains that same level of tension throughout the contraction SAME TENSION, CHANGING LENGTH

Describe an isometric ctraction

The length of the muscle doesn't change

What is "optimal length"?

The length of the muscle fiber @ which the most crossbridges can form allowing the fiber to generate almost 100% of the tension that is possible to produce.

What is the refractory period?

The muscle cannot respond to another stimulus.

What happens when immediate energy sources are depleted for muscles?

The muscle fibers turn to glycolysis (glycotic or anaerobic catabolism) to make ATP

Describe the synaptic cleft

The narrow space between the axon terminal and the muscle fiber into which Ach is released and enzymes that breaks down Ach.

motor end plate

The portion of the cell membrane at the neuromusclar junction; essentially the postsynaptic membrane at the synapse.

I band

The reginon of the sarcomere made up only of thin filaments. The I band is bisected by a Z line. I bands alternate with A bands to give skeletal and cardiac muscle a striated appearance. I bands get shorter (and may disappear completely) during muscle contraction.

H Zone

The region at the center of an A band of a sarcomere that is made up of myosin only. The H zone gets shorter (and may disappear) during muscle contraction.

H Zone & I Band

The region(s) of the sarcomere that shorten during muscle contraction.

What produces muscle tone?

The small amount of tension; due to involuntary activation of motor by the brain and spinal cord

sarcoplasmic reticulum

The smooth ER of a muscle cell, enlarged and specialized to act as a Ca2+ reservoir. The SR winds around each myofibril in the muscle cell.

What is the Neuromuscular Junction (NMJ) and what is its function?

The synapse of a motor neuron w/ a muscle fiber. Function: transmit a signal called a nerve impulse (action potential of the neuron).

Sarcomere

The unit of muscle contraction. Sarcomeres are bounded by Z lins, to which thin filaments attach. Thick filaments are found in the center of the sarcomere, overlapped by thin filaments over one another during contraction reduces the distance between Z lines, shortening the sarcomere.

What is the wave summation?

The waves of contraction added together. -Depends on the # of times per sec the muscle fiber is stimulated, we end up with one or two states: unfused tetanus and fused tetanus

What are satellite cells?

These cells have the ability to divide; these cells can help repair injured skeletal muscle.

Thin Filaments

These filaments are composed of actin, troponin, and tropomyosin.

Describe ligand-gated channels

They are in response to a chemical stimulus (ligands). They are also called chemically gated chemicals

Describe smooth muscle cells

They are long and flattened w 2 pointed end (spindle shaped). Single centrally located with an oval nucleaus. They line every hollow organ, line eyes, skin, and ducts of certain glands. They are linked by gap junctions. INVOLUNTARY.

Describe Action Potentials

They are quick/temporary change. Ability for the resting membrane potential to be altered to become more negative or positive.

Describe excitability:

They are responsive in presence of stimuli.

Cardiac muscle tissue is made up of:

They are striated muscles cells, shorter and wider, branched, only 1 or 2 nuclei, and has intercalated discs (contain gap junctions and tight). INVOLUNTARY

Describe intercalated discs

They contain gap junctions and are tight. They are found on cardiac tissue.

Describe Transverse tubules (T-Tubules)

They dive deeply into the muscle fiber and surround each myofibril. They for a tunnel-like network within the muscle.

Describe voltage-gated channels?

They respond to changes in membrane potential.

What are the 3 types of myofilaments?

Thick filaments, thin filaments, and elastic filaments.

Describe the Sliding-Filament Mechanism of Contraction

Thiin filaments slide past the thick filaments, generating tension throughout the whole sarcomere.

sliding filament mechanism

Thin filaments slide over thick filaments, by the z discs pulling together. The I band and H zone shorten, and the A band remains the same length

synaptic vesicles

Tiny pouches or sacs in the axon terminals that contain neurotransmitters

Describe endurance training

Training w/ a large increase in the frequency of motor unit activation and a moderate increase in force production - more repetitive w/ a lighter weight. (ex. cycling, jogging, cross-country skiing, distance swimming. Muscle fiber: - increased amounts of oxidative enzymes - more mitochondria and mitochondrial proteins - greater # of blood vessels - more Type I fibers

At rest, what holds the tropomyosin molecule in place?

Troponin

Which molecule does calcium bind to?

Troponin

What are the 2 main classes of skeletal muscle fibers?

Type I fibers and Type II fibers

Describe the type/s of smooth muscles and describe smooth muscles.

Type: smooth muscle. Smooth muscle cells lack striations. Located in the walls of hollow organs like the stomach and intestines. Line the vessels to cause vasoconstriction and vasodilation. They work automatically.

Name the types of striated muscles and describe striated muscle

Types: skeletal and cardiac. Striated muscles have striations (alternating light and dark bands)

What is the area within that has only thick filament?

What is the area within that has only thick filament?

I Band

What is the light area that has only thin filament?

What happens during a spasm?

When a muscle is unable to relax

Describe an isotonic concentric contraction (miometric contraction)

When the muscle shortens - the force generated by the muscle is greater than that of the external load.

What is the power stroke?

When the myosin pivots, pulling the actin toward the center of the sarcomere

Describe the electrical gradient or electrical potential

Where we have unequal #s of positive and negative ions separates by a barriers. represents a source of potential energy

Define hypertonia

a condition of the muscle may have abnormally high tone - feels rock hard - may shorten, causes painful joint contractures - occurs during shivering

Define myofibril

a long strand of cable like protein that contains thousands of actin - thin filaments and myosin - thick filaments

motor neuron

a neuron that sends an impulse to a muscle or gland, causing the muscle or gland to react (ACh released by a somatic motor fiber stimulates a skeletal muscle Acetylcholinesterase (AchE)= Responsible for degrading ACh and stopping the stimulation of the muscle fiber)

Epimysium

a sheath of fibrous elastic tissue surrounding a muscle.

Excitability

ability to respond to a stimulus

Contractility

ability to shorten when an adequate stimulus is received

The neurotransmitter used at the neuromuscular junction (NMJ) is__________.

acetylcholine

During muscle contraction, myosin crossbridges bind to active sites on:

actin

Thin filaments are composed of

actin, tropomyosin, troponin

Around how many muscle fibers does a motor unit contain?

around 150 muscle fibers.

Compared to Type I fibers, Type II fibers__________.

can generate faster, more powerful contractions

Thin Filiments

composed of: 3 proten molecules (actin, troponin, tropmyosin made up of primarily actin

M line(s)

connects thick filaments in a sarcomere; also run perpendicular to the long axis

Myofibrils

contains bundles of myofilaments which is inside repeating microscopic cylindrical units called sarcomers

sarcomere(s)

contractile units within myofibrils, the smallest contractile unit of a muscle

What does muscle tension do?

creates movement, maintains posture, stabilizes joints, generates heat, regulates the flow of materials through hollow organs.

The binding of a myosin head to an actin molecule is termed a:

crossbridge

A band(s)

dark areas, contain myosin and actin overlapping

What are the A bands?

dark region of a striation

terminal cisternae

dilated end-sacs of SR which cross the muscle fiber from one side to the other

Describe the 5 characteristics of skeletal muscle

excitability conductivity contractility elasticity Extensibility

Describe the axon terminal

extends an axon (long "arm) to muscle fiber. Axon swells to create axon terminal.

Describe the sarcomere

functional unit of contraction where muscle tension is produced. Extends from Z-disc to Z-disc. Includes: a full A band and half of two I bands.

What is the basic function of all muscle tissue?

generate muscle tension

What are myofilaments?

hundreds to thousands of protein bundles in a myofibril

Extensibility

is the ability of a cell that allows it to be stretched without being ruptured (up to 3 times their resting length without damage)

elasticity

is the ability of a cell that allows it to return to its original length after it has been stretched

Conductivity

is the ability of a cell to conduct electrical changes across the entire plasma membrane

The type of contraction in which length of the muscle fibers do not change is called:

isometric

The type of contraction that causes a skeletal muscle to lengthen is called__________.

isotonic eccentric contraction

What are the I bands

light region of a striation

The immediate result of acetylcholine binding to receptors on the motor end plate is_________.

local depolarization of the sarcolemma

myofibril

long protein cords that occupy sarcoplasm

Thick Filiments

made up of primarily myosin

What is the H zone?

middle area

What is the Na+/K+ ATPase pump

most important active transport pump for sodium and potassium. Moves 3 sodium ions out of the cell and 2 potassium ions into the cell (this needs ATP hydrolysis)

The folded region of sarcolemma found at the neuromuscular junction (NMJ) is called the_________.

motor end plate

Where are receptors for acetylcholine located?

motor end plate

A single motor neuron together with all the skeletal muscle fibers it innervates is called a:

motor unit

Larry's muscles weakened while he played tennis for hours on a hot summer afternoon. This inability to maintain intensity is defined as:

muscle fatigue

Thick filaments are composed of

myosin

Which of the following proteins is a component of thick filaments?

myosin

Which protein does NOT belong in a thin filament?

myosin

The synapse of a motor neuron with a muscle fiber is known as the:

neuromuscular junction

What are gated channels:

open or close only in response to some sort of stimulus.

What is the zone of overlap ?

over lapping filaments (where tension is generated during muscle contraction)

Through which ATP-generating mechanism can long-lasting muscle contractions be sustained?

oxidative catabolism

What is myoglobin?

oxygen-binding protein -binds to oxygen that has diffused into the muscle fiber from ECF and releases it as the available O2 is depleted by mitochondria performing oxidative catabolism (provides ATP for hours)

sarcolemma

plasma membrane of a muscle fiber

If a patient is given a drug that inhibits acetylcholinesterase (AChE), you would expect to see__________.

prolonged muscle contraction

Z Disc

provides anchorage for thin filaments and elastic filaments Separates the sarcomeres from each other A protein disc to which thin filaments and elastic filaments are anchored at each end of a sarcomere; appears as a narrow dark line in the middle of the I band.

Increase in tension by increasing the number of motor units that are stimulated is called_________.

recruitment

Define physical training

repetitive use of skeletal muscles that leads to changes in the structure and biochemistry of the muscle fibers.

During excitation contraction coupling calcium is released from the__________.

sarcoplasmic reticulum

The storage and release of calcium ions is the key function of the:

sarcoplasmic reticulum

Type I fibers lack:

speed

Describe the structure and function of Aponeurosis

strong flat white sheet of tissue that acts as a tendon to attach muscles to bone

When the sarcomere contracts and shortens__________.

the A band stays the same

Which of the following steps of the contraction cycle triggers ATP hydrolysis?

the binding of ATP to the myosin head

synaptic cleft

tiny gap between synaptic knob and muscle sarcolemma

What protein forms elastic filaments?

titin

What are elastic filaments composed of?

titin (resists excessive stretching, and provides elasticity)

The type of contraction represented by a single stimulus/contraction/relaxation sequence is a(n)__________.

twitch

What is the end line for each sarcomere?

z disk

identify the components of each line and band within the sarcomere

z line thin filaments thick filaments a band I band m line

Describe the smooth muscle function of regulation of flow

Controls the flow of materials through certain hollow organs by changing the diameter of teh tubes

Describe myofibrils

Cylindrical organelles; bundles of specialized proteins. Makes up 50-80% volume of the muscle cells.

sarcoplasm

Cytoplasm of a muscle fiber/cell

What is the sarcoplasm?

Cytoplasm of muscle cells that contains cytosol and all the organelles for the muscle cell.

Breakdown a muscle from big to small

Tendon --> Muscle (surrounded by epimysium) --> fascicle (surrounded by perimysium) --> muscle fiber (surrounded by endomysium) (sarcolemma is the cell membrane) --> myofibrils (sarcoplasm in between myofibrils) --> myofilaments ---> thick, thin, and elastic filaments.

Describe unfused tetanus

Tension pulsates, decreasing slightly and increasing a bit more w/ each successive twitch until a level of maximal tension is reached. Generates more tension than a single twitch contraction

Describe fused tetanus

Tension remains constant @ a maximal level, producing a sustained contraction. Tension is highest. Like unfused tetanus, it generates more tension than a single twitch contraction.

triad

The T Tubule and two terminal cisternae associated with it

Describe contractility

The ability to contract.

A Band

The band of the sarcomere that extends the full length of the thick filament. The A band includes regions of thick and thin filament overlap, as well as a region of thick filament only. A bands alternate with I bands to give skeletal and cardiac muscle a striated apperance. The A band does not shorten during muscle contraction.

A band

The band of the sarcomere that extends the full length of the thick filament. The A band includes regions of thick and thin filament overlap, as well as a region of thick filament only. A bands alternate with I bands to give skeletal and cardiac muscle a striated apperance. The A band does not shorten during muscle contraction.

Perimysium

The connective tissue that surrounds fascicles.

What does the end plate potential lead to?

The end plate potential leads to an action potential in the sarcolemma which in turn triggers events that result in contraction.

What enzyme catalyzes the Creatine Phosphate Reaction?

The enzyme creatine kinase catalyzes the reaction. Creatine phosphate donates a phosphate group to ADP, producing ATP

neuromuscular junction

The functional connection between the distal end of a nerve fiber and the middle of a muscle fiber ACh released, binds to ACh receptors ACh released by a somatic motor fiber stimulates a skeletal muscle

Define sarcomere

The functional contracting unit of skeletal muscle; the portion of myofibril between two Z lines

Where are intercalated discs only found in?

The heart

What is "muscular fatigue"?

The inability to maintain a given level of intensity of a particular exercise.

How many phases of muscle twitch are there? Describe each phase.

1. Latent period: 1- to 2-ms time that it takes for the action potential to spread through the sarcolemma. 2. Contraction period: this period is marked by a rapid increase in tension as cross bridge cycles occur repeatedly. 3. Relaxation period: tension decreases due to the decreasing calcium ion concentration in the cytosol.

Explain the functions of skeletal muscle

1. Produce skeletal movement 2. Maintain posture and body position 3. Support soft tissues 4. Guard entrances and exits 5. Maintain body temperature 6. Store nutrient reserves

What are the 3 processes of ATP regeneration?

1. Reactions in the cytosol that immediately add a phosphate group to ADP. 2. Glycolytic catabolism in cytosol. 3. Oxidative catabolism in mitochondria.

Describe the Exctitation-contraction coupling steps

1. The end-plate potential stimulates an action potential. 2. The action potential is propagated down the T-tubules. 3. T-tubule depolarization leads to the opening of calcium ion channel is in the SR, and calcium ions enter the cytosol.

Describe the steps of the Excitation phase

1. an action potential arrive @ the axon terminal (triggers exocytosis of the synaptic vesicles containing Ach) 2. synaptic vesicles relase Ach into synaptic cleft 3. Ach binds to ligand0gated ion channels in the motor end plate 4. ionchannels open and sodium ions enter the muscle fiber 5. entry of sodium ions depolarizes the sarcolemma locally, producing an end-plate potential (potential is simply a locaal depolarization in the area of the motor end plate.

Explain the function of blood vessels and nerves serving a muscle

Blood vessels deliver oxygen and nutrients to the muscle fibers, as well as remove waste from the muscle fibers. Nerves serve to allow muscles to move using motor neurons (voluntary muscles).

Define hypertrophy

Both # of myofibrils and diameter of the muscle fibers increase

Z disc

Separates the sarcomeres from each other A protein disc to which thin filaments and elastic filaments are anchored at each end of a sarcomere; appears as a narrow dark line in the middle of the I band.

What does autorhythmic mean?

Sets its own rhythm. An example would be PACEMAKER CELLS

The 3 types of muscle tissues and what they all have:

Skeletal, Cardiac, smooth. They all have muscle tension (a force)

What type of motor units does Type I muscle fibers contain?

Slow motor units

What is a muscle twitch?

Smallest muscle contraction is the response of a muscle fiber to a single action potential in a motor neuron.

Describe the repolarization stage

Sodium ion channels close while voltage gated potassium ion channels open and potassium ions leave the cell making membrane potential more negative again --> --85 mV

motor neuron

Somatic Motor Fibers: lead to the skeletal muscles

What is the primary function of the SR?

Storage and release of calcium ions (vital to muscle contraction and relaxation)

What are the 2 basic forms of muscle cells or fibers?

Striated and smooth

What is electrophysiology?

Study of electrical changes plasma membranes and the accompanying physiological processes.

Endomysium

Surrounds individual muscle fibers