A&P Chapter 10 Muscle

The region of the sarcomere containing the thick filaments is the

A band

Arrange the sequence of events at the NMJ from first to last. Rank the sequence of events at the NMJ that initiate an action potential in the muscle fiber, from first to last.

Action potential arrives at the axon terminal calcium ions enter the axon terminal synaptic vesicles fuse to the membrane of the axon terminal acetylcholine is released into the synaptic cleft acetylcholine binds to its receptors on the junctional folds junctional folds become depolarized action potential is initiated on the sarcolemma

What causes the release of calcium ions into the sarcoplasm from the terminal cisterns?

An action potential traveling along the t tubule

The binding of the neurotransmitter to receptors on the motor end plate causes what to occur?

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell.

What is responsible for muscle relaxation?

Calcium ions are removed from the sarcoplasm by active transport.

What is true about the difference between cardiac muscle cells and skeletal muscle cells?

Cardiac muscle cells have intercalated discs where skeletal muscle cells do not.

Rank the sequence of events in excitation-contraction coupling from first to last. Do not overlap any events.

Depolarization ofthe junctional folds triggers an actionpotential. Action potential travels along the sarcolemma. Action potential along the T tubules opens calcium channels. Calcium ions flood the sarcoplasm. Calcium ions bind to troponin. Troponin changes shape. Tropomyosin moves off of actin binding sites. Myosin heads form cross bridges with actin.

What is NOT a role of ATP in muscle contraction?

Exposing myosin binding sites on actin

EGTA is a substance that binds calcium ions. Imagine an experimental setup with a motor neuron and a muscle fiber. Stimulation of the motor neuron causes contraction of the muscle fiber through activity at the neuromuscular junction and excitation-contraction coupling. Now, inject the muscle fiber with EGTA. What effects would EGTA have on excitation-contraction coupling after the neuron releases acetylcholine at the neuromuscular junction?

It would prevent myosin from forming cross bridges with actin.

Identify the structure where ATP is produced.

Mitochondria

What structure most directly stimulates a skeletal muscle fiber to contract?

Motor neuron

Drag the appropriate events of excitation-contraction coupling to their respective order

Motor neuron signals muscle fiber contraction Sodium channels open along sarcolemma Action potential is conducted along T tubule Calcium ions are released Calcium ions bind to troponin Tropomyosin shifts position Myosin forms cross bridges with actin

What is true concerning motor units?

Movement of the eyeball requires fewer muscle fibers with less tension being produced.

Rank the sequence of cross bridge cycling, starting with the myosin-binding sites being exposed and ending with relaxation due to cross bridge cycling ending. Do not overlap any events.

Myosin head formscross bridge with actin Power strokemoves thin filament ATP attaches tomyosin head Cross bridges detach from actin Myosin head is re-energized Calcium ions pumped into the sarcoplasmic reticulum Calcium ion concentration decreases below the threshold for binding to troponin Myosin binding sites covered

nadequate calcium in the neuromuscular junction would directly affect what processes?

Release of acetylcholine from the synaptic vesicles

Which of the following is not characteristic of smooth muscle? Neurons that innervate smooth muscles are under involuntary control. The striations are due to the orderly arrangement of actin and myosin. Smooth muscle cells are uninucleate. The thin filaments of smooth muscle fibers are attached to dense bodies. Smooth muscles do not contain sarcomeres.

The striations are due to the orderly arrangement of actin and myosin.

The soleus muscle is very red in color. Which of these statements about soleus muscle fibers is FALSE? They are slow to fatigue. They have a slow twitch speed. They are large in diameter. They are rich in myoglobin

They are large in diameter.

Myasthenia gravis is a disease resulting from an autoimmune attack on the ACh receptors of the motor end plate. Binding of antibodies to the ACh receptors results in generalized muscle weakness that progresses as more ACh receptors are destroyed. What medication would help alleviate the muscle weakness?

a drug that binds to and inactivates acetylcholinesterase (neostigmine)

Acetylcholine receptor

a type of chemically-gated ion channel located on the junctional folds of the muscle fiber.

Calcium channel

a type of voltage-gated ion channel located on the axon terminal.

Sodium channel

a type of voltage-gated ion channel located on the sarcolemma of the muscle fiber.

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

acetylcholine (ACh)

Which of the following is NOT an effect that exercise will have on muscle tissue? an increase in the amount of tension produced when the muscle contracts an increase in the number of myofibrils an increase in the amount of fibrous connective tissue higher concentration of glycolytic enzymes

an increase in the amount of fibrous connective tissue

Tropomyosin

block(s) binding sites on actin.

Smooth muscle contracts when calcium binds to __________ and activates _________

calmodulin; myosin light chain kinase

Troponin

change(s) shape upon binding with calcium ions.

When a muscle is stimulated repeatedly at a high rate, the amount of tension gradually increases to a steady maximum tension. This state of maximum tension is called

complete tetanus

T tubule

conduct(s) action potentials throughout the interior of the muscle fiber.

Conduction of an action potential along the sarcolemma depends upon ___________.

diffusion of sodium ions through voltage-gated channels

What is the function of the T tubules?

distribute action potentials throughout the interior of the skeletal muscle cell

Characteristics of skeletal muscle fibers include all of the following EXCEPT that __________. each fiber is striated skeletal muscle fibers are very large each fiber contains a single nucleus each fiber is multinucleated

each fiber contains a single nucleus

The capillaries that wrap around each muscle fiber are located within the __________.

endomysium

Acetylcholinesterase

enzyme located in the synaptic cleft that breaks down acetylcholine

The dense layer of connective tissue that surrounds an entire skeletal muscle is the

epimysium.

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

exocytosis

What allows muscles to return to their original shape during relaxation?

gravity, opposing muscle contractions, and elastic forces

A fascicle is a

group of muscle fibers that are encased in the perimysium.

A weight-lifter strains to lift a heavy weight and there is no movement of the person's arms holding on to the weight. This type of contraction is called a(n) ________ contraction.

isometric

During the time when the action potential moves through the sarcolemma a muscle twitch is in

latent period.

Synaptic vesicle

membranous sac located in the axon terminal that contains neurotransmitter.

A single motor neuron together with all the muscle fibers it innervates is called a(n)

motor unit.

To produce wave summation

must be stimulated again before it has relaxed from the previous stimulation

Acetylcholine

neurotransmitter that stimulates skeletal muscle contraction.

Resting smooth muscle can be stretched without affecting tension development because of its ________

plasticity

Skeletal muscle does each of these EXCEPT __________ pump blood maintain posture produce movement store nutrients

pump blood

Which of these is NOT a function of smooth muscle? adjusting airway diameter churning the stomach contents pushing blood into the great vessels of the heart elevating skin hairs

pushing blood into the great vessels of the heart

Junctional folds

receive(s) stimulus from the motor neuron.

Detachment of myosin cross-bridges occurs during the

relaxation phase.

Terminal cistern

release(s) calcium ions into the sarcoplasm.

Which of the following best describes the term sarcomere?

repeating unit of striated myofibrils

The plasma membrane of a skeletal muscle fiber is called the

sarcolemma.

How is acetylcholine (ACh) removed from the synaptic cleft?

simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)

The type of muscle fiber that is most resistant to fatigue is the ________ fiber

slow

What is the function of the sarcoplasmic reticulum?

storage of calcium

At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium, come together to form a

tendon.

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?

terminal cisterns (cisternae) of the sarcoplasmic reticulum

Which of the following statements correctly describes the structure of the I band?

the region of the sarcomere that contains only thin filaments

Synaptic cleft

the space between the axon terminal and junctional folds.

Each thin filament consists of

two actin protein strands coiled helically around each other

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

voltage-gated calcium channels