Chapter 10 multiple choice

Neuromuscular junction at rest

-No Na+ diffusion, chemically-gated channels closed, calcium channels closed, more negative charges inside sarcolemma, Ach in synaptic vesicles

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

1. Action potential arrives at the axon terminal. 2. Calcium ions enter the axon terminal 3. Synaptic vesicles fuse to membrane of axon terminal 4. Acetylcholine is released into the synaptic cleft 5. Acetylcholine binds to its receptors in the junctional folds 6. Junctional folds become depolarized 7. Action potential is initiated on the sarcolemma

Cross bridge cycling sequences, starting with myosin binding sites being exposed and ending with excitation due to cross bridge cycling ending.

1. Myosin heads form cross bridge with actin. 2. Power stroke moves thin filament. 3. ATP attaches myosin head. 4. Cross bridges detach from actin. 5. Myosin head is reenergized. 6. Calcium ions pumped into the sarcoplasmic reticulum. 7. Calcium ion concentration decreases below threshold for binding to troponin. 8. Myosin binding sites covered.

Put the following structures in order from superficial to deep. 1. muscle fiber 2. perimysium 3. myofibril 4. fascicle 5. endomysium 6. epimysium

6, 2, 4, 5, 1, 3

What is a motor unit?

A motor neuron and all of the muscle fibers it supplies

Which of the following choices best summarizes excitation-contraction coupling?

A series of events in which an electrical stimulus is conveyed to a muscle fiber to enact contraction

A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?

A series of proteins that control calcium release.

Which of the following best describes how ACh changes the ion permeability of the sarcolemma?

ACh binds to receptors in the junctional folds.

Which of the following best describes the role of acetylcholinesterase molecules at the neuromuscular junction?

Acetylcholinesterase breaks down ACh, which allows chemically gated ion channels to close.

Neuromuscular junction active

Ach in synpatic cleft, chemically-gated channels open, less negative charges inside sarcolemma, Na+ diffusion, calcium channels open

Which of the choices below correctly describes how an action potential generated at the neuromuscular junction (NMJ) is converted to excitation in the muscle fiber?

An action potential in the motor neuron causes ACh to be released into the synaptic cleft. Binding of ACh to sarcolemma receptors initiates graded potentials.

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 cause what to occur?

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate

The binding of a 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) and sodium enters the cell.

The sarcoplasmic reticulum contains

Calcium

Which selection correctly describes the role of calcium in coupling?

Calcium binds to troponin, which moves tropomyosin and exposes the myosin-binding sites on actin.

Which of the following is responsible for preventing a muscle from contracting?

Calcium ions are removed from the sarcoplasm by active transport.

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?

Calcium release from the sarcoplasmic reticulum initiates the contraction.

Branching striated with intercalated discs, aerobic metabolism

Cardiac muscle

What type of metabolism for quick heavy lifting?

Direct phosphorylation

The term excitation refers to which step in the process?

Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.

Which of the following is NOT a role of ATP in muscle contraction?

Exposing myosin binding sites on actin

Decreases in length or distance

I band, length of h zone, distance between Z discs

How does the shape change of these proteins lead to contraction?

It allows calcium to exit the sarcoplasmic reticulum and enter the cytosol.

What is the cross bridge cycle?

It is the cycle in which an energized myosin head binds to actin and performs a power stroke, then binds to ATP in order to detach and re-energize.

No change in length or distance

Length of A band, length of thick filament, length of thin filament

Aerobic metabolism

Metabolism that can proceed only in the presence of oxygen.

Which selection best describes the initial event in contraction?

Myosin heads bind to the newly exposed myosin-binding sites on actin to form cross bridges.

Troponin, a major protein in thin filaments, is a globular protein with three polypeptide subunits. Which of the following is NOT a function of the troponin?

One subunit binds to potassium ions.

Fast twitch

Rapid intense movement, anaerobic respiration, white muscles

Voluntary contraction, long and striated with many nuclei, aerobic and anaerobic metabolism

Skeletal muscle

Tapered with no striations and one nucleus, slowest contraction, aerobic metabolism.

Smooth muscle

The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by

T tubules

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

T-tubule

Anaerobic metabolism (glycolysis)

The metabolism that takes place without oxygen; the principle product is lactic acid.

What happens immediately after the myosin head binds to the active site on actin?

The myosin head pivots, moving the actin strand.

When an action potential arrives at an axon terminal of a motor neuron, which ion channel opens?

Voltages gated calcium channels

A muscle producing almost peak tension during rapid cycles of contraction and relaxation is said to be in __________. a. incomplete tetanus b. treppe c. complete tetanus d. recruitment

a

Acetylcholine receptors are primarily located __________. a. on the motor end plate b. inside the muscle fiber c. inside vesicles d. on the synaptic terminal

a

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

a

Which of the following is an example of an isometric contraction? a. holding a heavy stack of books above the ground b. flexing the biceps muscle while holding a 10-pound weight c. picking up a toddler who is sitting on the floor d. walking

a

Which of the following is involved in the power stroke? a. myosin b. tropomyosin c. myofibrils d. Z lines

a

Which type of skeletal muscle fibers has low fatigue resistance? a. fast fiber b. intermediate fiber c. slow fiber d. type I fiber

a

Which part of the sarcomere shortens during contraction? a. I band, length of h zone, distance between Z discs b. length of A band, length of thick filament, length of thin filament

a. I band, length of h zone, distance between Z discs

The skeletal muscle complex known as the triad consists of a. a transverse tubule and two terminal cisternae. b. actin, myosin, and sarcomeres. c. filaments, myofibrils, and sarcomeres. d. A bands, H bands, and I bands.

a. a transverse tubule and two terminal cisternae.

A type of voltage-gated ion channel located on the axon terminal is a a. calcium channel b. synaptic terminal c. acetylcholine receptor

a. calcium channel

Peak tension production occurs when all motor units in the muscle contract in a state of __________. a. complete tetanus b. wave summation c. twitch d. treppe

a. complete tetanus

A fascicle is a a. group of muscle fibers that are encased in the perimysium. b. group of muscle fibers that are all part of the same motor unit. c. collection of myofibrils in a muscle fiber. d. layer of connective tissue that separates muscle from skin.

a. group of muscle fibers that are encased in the perimysium.

_________ receive(s) stimulus from the motor neuron. a. junctional folds b. actin c. motor end plate d. synaptic vesicle

a. junctional folds

Skeletal muscle does each of these EXCEPT __________. a. pump blood b. maintain posture c. produce movement d. store nutrients

a. pump blood

At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium, come together to form a a. tendon. b. tenosynovium. c. sheath. d. ligament.

a. tendon

neurotransmitter that stimulates skeletal muscle contraction

acetylcholine

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

acetylcholine receptor

which of the following proteins listed below would be most associated with the excitability?

acetylcholine receptors in the motor end plate

enzyme located in the synaptic cleft that breaks down acetylcholine

acetylcholinesterase

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

acetylcholinesterase destroying the ACh

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

actin

Which of the following proteins contains the active site involved in cross bridge formation

actin

Which of the following proteins contains the active site involved in cross-bridge formation?

actin

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

The most important factor in decreasing the intracellular concentration of calcium ion after contraction is

active transport of calcium into the sarcoplasmic reticulum

As long as muscle has enough oxygen, ATP is formed by

aerobic metabolism

When exercise demands exceeds the muscle cells ability to carry out reactions fast enough, ATP is formed by

anaerobic metabolism

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

arrival of an action potential

The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by __________. a. myofibrils b. T tubules c. myofilaments d. the sarcoplasmic reticulum

b

What is name given to the regularly spaced infoldings of the sarcolemma? a. terminal cisternae b. transverse or T tubules c. sarcoplasmic reticulum d. motor endplates

b

Where are calcium ions stored in the muscle cell? a. cytosol b. terminal cisternae of the sarcoplasmic reticulum c. sarcolemma d. T tubule

b

Which of the following most correctly describes excitation in the context of excitation-contraction coupling in skeletal muscle? a. the release of calcium by the sarcoplasmic reticulum b. the generation of an action potential in the sarcolemma c. the binding of calcium to troponin d. the formation of cross-bridges

b

Which of the following events most directly occurs due to an action potential generated by the motor neuron? Choose the best answer. a. An action potential is generated on the muscle fiber. b. ACh is released at the synapse. c. Na rushes into the sarcolemma. d. AChE breaks down ACh in the synaptic cleft.

b. ACh is released at the synapse.

Which of the following statements describes a critical event that occurs at the neuromuscular junction? a. When the action potential reaches the end of the axon terminal, voltage-gated sodium channels open and sodium ions diffuse into the terminal. b. Acetylcholine is released by axon terminals of the motor neuron. c. Acetylcholine binds to its receptor in the junctional folds of the sarcolemma. Its receptor is linked to a G protein. d. Acetylcholine is released and moves across the synaptic cleft bound to a transport protein.

b. Acetylcholine is released by axon terminals of the motor neuron.

The cross bridge cycle starts when _________. a. Ca2+ is actively transported into the sarcoplasmic reticulum b. Ca2+ from the sarcoplasmic reticulum binds to troponin c. acetylcholine diffuses away from the synaptic cleft d. ATP binds to troponin and is hydrolyzed to ADP and Pi

b. Ca2+ from the sarcoplasmic reticulum binds to troponin

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

b. Calcium ions bind to tropomyosin and change its shape.

The region of the sarcomere that always contains thin filaments is the a. M line. b. I band. c. H band. d. Z line.

b. I band.

Calcium entry into the axon terminal triggers which of the following events? a. Acetylcholine binds to its receptor. b. Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine. c. Acetylcholine is released into the cleft by active transporters in the plasma membrane of the axon terminal. d. Cation channels open and sodium ions enter the axon terminal while potassium ions exit the axon terminal.

b. Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

Which of the following is responsible for muscle relaxation? a. sodium ions enter into the sarcoplasm through voltage-gated channels. b. calcium ions are removed from the sarcoplasm by active transport. c. ATP binds to the myosin head to cause cross bridge detachment. d. calcium ions are released from the terminal cisterns during depolarization of the T tubule.

b. calcium ions are removed from the sarcoplasm by active transport.

A layer of connective tissue that surrounds each individual muscle fiber is called the __________. a. epimysium b. endomysium c. tendon d. perimysium

b. endomysium

The dense layer of connective tissue that surrounds an entire skeletal muscle is the a. tendon. b. epimysium. c. endomysium. d. perimysium.

b. epimysium.

Which part of the sarcomere stays almost the same size during contraction? a. I band, length of h zone, distance between Z discs b. length of A band, length of thick filament, length of thin filament

b. length of A band, length of thick filament, length of thin filament

Skeletal muscle cells are stimulated to contract by a. motor units b. motor neurons c. sarcomeres d. acetylcholine

b. motor neurons

Skeletal muscle fibers are formed from embryonic cells called a. myofibrils. b. myoblasts. c. sarcomeres. d. fascicles.

b. myoblasts.

Cross-bridges are portions of a. actin molecules. b. myosin molecules. c. calcium ions. d. tropomyosin molecules.

b. myosin molecules.

Which type of muscle tissue has the greatest effect on the body's heat production? a. cardiac b. skeletal c. smooth d. All of these muscle types have about the same effect on the body's heat production.

b. skeletal

What causes the myosin head to disconnect from actin?

binding of ATP

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

c

The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________. a. synaptic cleft b. acetylcholine receptor c. synaptic terminal d. motor end plate

c

The narrow space between the axon terminal and the motor end plate is called the a. axon b. sarcolemma c. synaptic cleft d. vesicle

c

The region of the sarcomere containing the thick filaments is the a. M line. b. I band. c. A band. d. Z line.

c. A band

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur? a. Binding causes potassium voltage-gated channels to open in the motor endplate. b. Binding causes voltage-gated sodium channels to open in the motor endplate. c. Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate. d. Binding causes chemically gated potassium channels to open in the motor end plate.

c. Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.

The area of the A band in the sarcomere consists of __________. a. Z line, H band, and M line b. thin filaments only c. M line, H band, and zone of overlap d. thick filaments only

c. M line, H band, and zone of overlapx

In a sarcomere, the central portion of thick filaments are linked laterally by proteins of the a. I band. b. A band. c. M line. d. Z line.

c. M line.

Which of the following is NOT a role of ATP in muscle contraction? a. Transporting calcium ions into the sarcoplasmic reticulum b. Detaching the cross bridge from actin c. Transporting calcium ions into the sarcoplasmic reticulum

c. Transporting calcium ions into the sarcoplasmic reticulum

A type of chemically-gated ion channel located on the junctional folds of the muscle fiber is a. calcium channel b. synaptic terminal c. acetylcholine receptor

c. acetylcholine receptor

In an isotonic contraction, __________. a. muscle length does not change as a result of the resistance b. tension in the muscle decreases as the resistance increases c. cross-bridges must produce enough tension to exceed the load to be moved d. tension in the muscle varies as the muscle shortens

c. cross-bridges must produce enough tension to exceed the load to be moved

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________. a. extend from the spinal cord to the sarcolemma of a skeletal muscle fiber b. arise in the epimysium of a skeletal muscle and extend to individual skeletal muscle fibers c. extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber d. extend from the brain to the sarcolemma of a skeletal muscle fiber

c. extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

Chemicals released by the neuron that sends a message to another cell a. ACh b. synaptic vesicles c. neurotransmitters d. motor neurons

c. neurotransmitters

The plasma membrane of a skeletal muscle fiber is called the a. sarcoplasm. b. sarcosome. c. sarcolemma. d. sarcoplasmic reticulum.

c. sarcolemma.

Each thin filament consists of a. a double strand of myosin molecules. b. a rod-shaped structure with "heads" projecting from each end. c. two actin protein strands coiled helically around each other. d. chains of myosin molecules.

c. two actin protein strands coiled helically around each other.

What are responsible for the exposure of the myosin binding sites on actin?

calcium ions

What is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?

calcium ions

Sarcomeres are functional units of ________ muscle.

cardiac and skeletal only

Stimulation of the muscle with no relaxation

complete tetany

A muscle cell runs out of ATP. Even though these are cyclic reactions, what step of the cross bridge cycle given is most directly inhibited or terminated?

cross bridge detachment

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

d

What causes cross bridge detachment? a. Acetylcholine binds to receptors in the junctional folds of the sarcolemma. b. Calcium ions bind to troponin. c. ADP and inorganic phosphate are bound to the myosin head. d. ATP binds to the myosin head.

d

What causes the vesicles inside a neuron to fuse with the plasma membrane? a. acetylcholine binding to acetylcholine receptors b. an action potential in the muscle fiber c. acetylcholine being broken down by acetylcholinesterase d. an action potential in the neuron

d

What specific event initiates the contraction? a. Voltage-sensitive proteins change shape. b. Action potentials propagate into the interior of the skeletal muscle fiber. c. Sodium release from the sarcoplasmic reticulum initiates the contraction. d. Calcium release from the sarcoplasmic reticulum initiates the contraction.

d

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers? a. Acetylcholine. b. Sodium ions. c. Action potentials. d. Calcium ions.

d

Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers? a. through electrical impulses travelling along the sarcolemma b. through T tubules c. through cross-bridge formation d. through calcium release from the sarcoplasmic reticulum

d

The area in the center of the A band that contains no thin filaments is the a. M line. b. zone of overlap. c. Z line. d. H band.

d. H band.

Folded portion of the sarcolemma located at the neuromuscular junction a. sarcoplasm b. motor neuron c. motor unit d. motor end plate

d. motor end plate

A thin layer of connective tissue that surrounds a muscle fascicle is called the __________. a. epimysium b. endomysium c. tendon d. perimysium

d. perimysium

Which of the following best describes the term titin? a. thin filaments are anchored here b. largely made of myosin molecules c. storage and release site for calcium ions d. protein that accounts for elasticity of resting muscle

d. protein that accounts for elasticity of resting muscle

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

d. release of acetylcholine from axon terminals at the neuromuscular junction

The structural theory that explains how a muscle fiber contracts is called the ________ theory. a. muscle contraction b. action-myosin interaction c. excitation-contraction coupling d. sliding filament

d. sliding filament

Which of these statements about skeletal muscles is FALSE? a. They store nutrient reserves. b. They support soft tissues. c. They pull on tendons. d. Their fibers branch.

d. their fibers branch.

At rest, active sites on the actin are blocked by a. myosin molecules. b. calcium ions. c. ATP molecules. d. tropomyosin molecules.

d. tropomyosin molecules.

ATP binding leads to which of the following actions

detaching and resetting cross-bridges

ATP binding leads to which of the following actions?

detaching and resetting cross-bridges

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

diffusion of sodium ions through voltage-gated channels

Where in the cross bridge cycle does ATP hydrolysis occur?

during the cocking of the myosin head

What surrounds the individual muscle cell?

endomysium

Place the connective tissue sheaths of skeletal muscle, in order from internal to external

endomysium, perimysium, and epimysium

What is the functional role of the T tubules?

enhance cellular communication during muscle contraction

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

exocytosis

Inside a muscle, bundles of single muscle fibers form __________.

fascicles

during an exercise where muscles do not shorten, ____________ contractions have occured

isometric

receive(s) stimulus from the motor neuron.

junctional folds

Receptors for acetylcholine are located on the

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

The neuromuscular junction is a connection between a neuron and a __________.

muscle fiber

eccentric contraction

muscle lengthens, ex. Walking up a steep hill, bicep curl

concentric contraction

muscle shortens, ex. Picking up a book

The contractile units of skeletal muscles are ________.

myofibrils

the two proteins directly involved in muscle contraction are broadly called ___________

myofilaments

Which of the following is involved in the power stroke

myosin

Each skeletal muscle fiber is controlled by a motor neuron at a single

neuromuscular junction

The ________________ _______________ is where a neuron and muscle fiber come in close contact

neuromuscular junction

Rigor mortis occurs because ________.

no ATP is available to release attached actin and myosin molecules

Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________.

no muscle tension could be generated

What causes the power stroke?

release of ADP and Pi

After the release of acetylcholine, it binds receptors on the __________________.

sarcolemma

the cell membrane of a muscle fiber is the ____________

sarcolemma

What is the functional unit of a skeletal muscle called?

sarcomere

Z lines define the edges of which of the following

sarcomeres

Z lines define the edges of which of the following?

sarcomeres

Which organelle completely surrounds each myofibril inside a muscle fiber?

sarcoplasmic reticulum

which muscle cell structure store calcium ions that are used to trigger the contraction?

sarcoplasmic reticulum

How is ACh removed from the synaptic cleft?

simple diffusion away from the synaptic cleft and AChE

which of the following statements is true? (skeletal muscle...)

skeletal muscle cells are long and cylindrical with many nuclei

which of the following are correctly paired?

skeletal muscle, voluntary control

Treppe (staircase effect) the

stepwise increase in contraction tension, muscle is allowed to completely relax

Slow twitch

sustained contraction, aerobic metabolism, red muscles

Gap between motor neuron and muscle fiber

synaptic cleft

the space between the axon terminal and junctional folds

synaptic cleft

A membranous sac located in the axon terminal that contains a neurotransmitter

synaptic vesicle

membranous sac located in the axon terminal that contains a neurotransmitter

synaptic vesicle

Where are neurotransmitters stored?

synaptic vesicles in the axon terminal

release(s) calcium ions into the sarcoplasm.

terminal cistern

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 cisternae of the sarcoplasmic reticulum

what is the most distinguishing characteristic of muscle tissue?

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

Which of the following most correctly describes excitation in the context of excitation contraction coupling in skeletal muscle

the generation of an action potential in the sarcolemma

Which of the following acts as an ATPase during the contraction cycle of muscle?

the head portion of the myosin molecule

An action potential in the muscle fiber causes __________.

the muscle fiber to contract

the contractile, or functional, unit of a muscle fiber is ____________

the sarcomere

which of the following proteins listed below would be most associated with contractility?

thick (myosin) filaments

Wave summation

this occurs when a second stimulus is received before the muscle fiber has relaxed, creating a second contraction that is stronger than the first

Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers

through calcium release from the sarcoplasmic reticulum

The action potential is conducted into a skeletal muscle fiber by

transverse tubules

T tubules and the terminal cisternae are clustered into structures called

triads

When is sarcomeres at rest what is covering the active sites on actin

tropomyosin

When the sarcomere is at rest, what is covering the active sites on actin?

tropomyosin

______________ has an affinity for myosin binding sites in the absence of calcium

tropomyosin

Which of the following causes the active site on actin to be exposed or uncovered

tropomyosin shifting position

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

troponin

To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers

troponin

When calcium is released inside a muscle cell what does it bind to

troponin

When calcium is released inside a muscle cell, what does it bind to?

troponin

change(s) shape upon binding with calcium ions.

troponin

Inside a neuron, acetylcholine is contained within __________.

vesicles

When an action potential arrives at an axon terminal of a motor neuron, which ion channel opens?

voltage gated calcium channels

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

voltage-gated calcium channels