Exam 4: Chapter 9 Muscles and Muscle Tissue

Skeletal muscle

Muscle tissue that is the longest of all muscle and have striations (stripes). Also called voluntary muscle

Cardiac Muscle

Muscle tissue only found in the heart. Is striated and rhythmic, also contains intercalated discs

Smooth Muscle

Muscle tissue found in walls of hollow organs and is involuntary.

Excitability (responsiveness)

The ability to receive and respond to stimuli

Contractibility

ability to shorten forcibly when stimulated

Extensibility

ability to be stretched

Elasticity

ability to recoil to resting length

produce movement

One of four important muscle functions. Skeletal muscles are responsible for locomotion and manipulation

Maintain posture and body position

One of four important muscle functions. Resisting the never-ending downward pull of gravity.

stabilize joints

One of four important muscle functions. Even as they pull on bones to cause movement, they strengthen and stabilize the joints of the skeleton

generate heat as they contract

One of four important muscle functions. Helps maintain normal body temperature

Insertion

attachment of muscle to movable bone

Origin

attachment of a muscle that remains relatively fixed during muscular contraction

Origin

attachment of a muscle that remains relatively fixed during muscular contraction

Perimysium

fibrous connective tissue surrounding entire fascicles (groups of muscle fibers)

Endomysium

fine areolar connective tissue surrounding each muscle fiber

Sarcolemma

Cell membrane of the muscle fiber

Myofibrils

Located inside of the muscle fiber

Sarcoplasm

muscle fiber cytoplasm

Myofilaments

The contractile proteins, actin and myosin, of muscle cells

thin filaments

Actin myofilaments are thin or thick?

Z discs

Where do actin myofilaments anchor?

thick filaments

Myosin filaments are thin or thick?

M line

Where do myosin filaments connect?

The length of the A band

How long to myosin filaments extend?

Sarcomere

Functional unit of muscle. Area between the Z discs

I-band

Actin (thin filament) only

H zone

Myosin (thick filament) only

A-band

Entire myosin filament

Composition of Myosin

Contains myosin molecule that has myosin heads

composition of actin

Contains actin, troponin, and tropomyosin

sarcoplasmic reticulum (SR)

Network of smooth endoplasmic reticulum surrounding each myofibril. Stores and releases Calcium

T tubules

Tube formed by protrusion of sarcolemma deep into cell interior

function of T tubules

allow electrical nerve transmissions to reach deep into interior of each muscle fiber

Sliding filament model of contraction

states that during contraction the thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree

Thin filaments (actin)

In sliding filament model of contraction which filament (actin or myosin) slides toward the end line

Neither thick or thin change length

Do thick or thin filaments change length during contraction

Myosin heads bind with actin

What forms the cross bridge during contraction

pulled toward M line

What happens to the Z discs during contraction

they shorten

What happens to I bands during contraction

H zones

Which zones disappear during contraction

A bands move closer to each other

What do A bands do during contraction

synaptic cleft

What separates the Axon terminal and muscle fiber

synaptic vesicles

What contains the neurotransmitter acetylcholine (ACh)?

Within axon terminals

Where are synaptic vesicles stored?

Infoldings of sarcolemma

What contains millions of ACh receptors

Action Potential (AP)

What arrives at the axon terminal?

voltage-gated calcium channels

What channels open up allowing calcium into the motor neuron

calcium entry

What causes the release of ACh into synaptic cleft

ACh receptors (Sodium chemical gates)

What does the ACh diffuse across to

Opens the Sodium chemical gates allowing Sodium to enter

What happens when ACh binds to the ACh receptors

end plate potential

What is the result of Sodium entering the muscle fiber

Acetylcholinesterase

What breaks down ACh

Inside

Is the inside or outside of the muscle cell negatively charged?

Changes in electrical charges

What causes Action Potential

generation of end plate potential, depolarization, repolarization

What are the three steps of Generating Action Potential

ACh receptors on the sarcolemma

In creating end plate potential where does the ACh released from the motor neuron bind to?

they open up

When ACh binds to the ACh receptors on the sarcolemma what happens to chemically gated ion channels (ligands)?

Sodium ions

When the chemically gated ion channels open what diffuses into the muscle fiber?

Potassium ions

When the chemically gated ion channels open what diffuses out of the muscle fiber?

end plate potential (EPP)

When the Sodium diffuses into the muscle fiber the interior of the sarcolemma become more positive. What is the result of this?

Depolarization

generation and propagation of an action potential (AP)

Threshold

What is the critical point that the membrane voltage has to reach in order for the voltage-gated Sodium channels to open

True

Once the voltage hits threshold it cannot stop contraction. True or False?

Repolarization

restoration of resting conditions

They close

In repolarization what happens to Sodium voltage-gated channels

they open

In repolarization what happens to voltage-gated Potassium channels?

It rapidly brings cell back to initial resting membrane voltage

What happens when there is a Potassium efflux out of the cell?

refractory period

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

sodium-potassium pump

What restores the ionic conditions of the cell

excitation-contraction coupling

AP is propagated along sarcolemma and down into the T Tubules, where voltage-sensitive proteins in tubules stimulate Calcium release from Sarcoplasmic reticulum

Calcium release

What leads to contraction in excitation-contraction coupling

It blocks active sites of actin

In Cross Bridge cycling when there is a low intracellular Calcium concentration what is the role of Tropomyosin

The myosin heads cannot attach to actin

In Cross Bridge Cycling what happens to myosin heads when there is a low intracellular Calcium concentration?

The Muscle fiber remains relaxed

What happens to the muscle fibers when there is a low intracellular Calcium concentration in Cross Bridge Cycling?

calcium binds to troponin

When there is a high intracellular Calcium concentration what does Calcium do?

Troponin changes shape and moves tropomyosin away from myosin-binding sites

What happens when Calcium attaches to Troponin

Myosin heads can attach to actin

What happens after Troponin moves the tropomyosin away from the myosin-binding sites?

Cross Bridge

What is it called when myosin heads bind to actin?

cross bridge formation

High energy myosin head attaches to actin active site

working (power) stroke

myosin head pivots and pulls actin filament toward the M line

cross bridge detachment

ATP attaches to myosin head, causing cross bridge to detach

cocking of myosin head

Energy from hydrolysis of ATP 'cocks' myosin head into high-energy state

In the power stroke

What is the energy gained during the cocking of myosin head used for in the next cross bridge cycle?

isometric contraction

no shortening; muscle tension increases but does not exceed load

isotonic contraction

muscle shortens because muscle tension exceeds load

motor neurons

The nerve-muscle functional unit

muscle twitch

a muscle fiber's response to a single action potential from motor neuron

myogram

a chart of the timing and strength of a muscle's contraction

Tracing

Line recording contraction activity

latent period

events of excitation-contraction coupling; no muscle tension

period of contraction

cross bridge formation; tension increases

period of relaxation

Ca2+ reentry into SR; tension declines to zero

faster

Does muscle contract faster or slower than it relaxes

graded muscle responses

What is required for proper control of skeletal movement?

frequency and strength of stimulation

What are responses graded by?

Single contractile response

What does a single stimulus result in?

temporal summation

results from two stimuli arriving close together

Unfused Tetanus (Muscle spasm)

Increase in stimulus frequency causes muscle to progress to sustained, quivering contraction

fused tetanus

When the contractions fuse into one smooth sustained contraction plateau