Anatomy chapter 10

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. Calcium bound to troponin C. ATP bound to a myosin head D. Troponin bound to tropomyosin

A. A myosin head bound to actin

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

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

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur? A. Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate. B. Binding causes chemically gated potassium channels to open in the motor end plate. C. Binding causes potassium voltage-gated channels to open in the motor endplate. D. Binding causes voltage-gated sodium channels to open in the motor endplate.

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

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

A. Calcium ions bind to troponin and change its shape.

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers? A. Calcium ions. B. Acetylcholine. C. Action potentials. D. Sodium ions

A. Calcium ions.

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction? A. Calcium release from the sarcoplasmic reticulum initiates the contraction. B. Action potentials propagate into the interior of the skeletal muscle fiber. C. Voltage-sensitive proteins change shape. D. Sodium release from the sarcoplasmic reticulum initiates the contraction.

A. Calcium release from the sarcoplasmic reticulum initiates the contraction.

Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process? A. Excitation, in this case, refers to the propagation of action potentials along the sarcolemma. B. Excitation refers to the shape change that occurs in voltage-sensitive proteins in the sarcolemma. C. Excitation refers to the release of calcium ions from the sarcoplasmic reticulum. D. Excitation refers to the propagation of action potentials along the axon of a motor neuron

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

What structure is the functional unit of contraction in a skeletal muscle fiber? A. The sarcomere B. The triad C. The junctional folds of the sarcolemma D. The cross bridge

A. The Sarcomere

Malignant hyperthermia (MH) is a rare genetic disease in which the sarcoplasmic reticulum leaks calcium when the patient is put under general anesthesia. Which of the following best describes how anesthesia would affect the skeletal muscles of a patient with MH? A. The muscles would contract because of calcium binding to troponin. B. The muscles would relax because of calcium being pumped back into the sarcoplasmic reticulum. C. The muscles would contract because of increased action potential generation in the sarcolemma. D. The muscles would contract because of increased nerve stimulation.

A. The muscles would contract because of calcium binding to troponin.

How is acetylcholine (ACh) removed from the synaptic cleft? A. acetylcholinesterase (AChE; an enzyme) B. diffusion away from the synaptic cleft C. a reuptake pump on the axon termina

A. acetylcholinesterase (AChE; an enzyme)

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

A. an action potential in the neuron

Which of the following is involved in the power stroke? A. myosin B. Z lines C. tropomyosin D. myofibrils

A. myosin

Which organelle completely surrounds each myofibril inside a muscle fiber? A. sarcoplasmic reticulum B. calcium C. nucleus D. fascicle

A. sarcoplasmic reticulum

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

A. the generation of an action potential in the sarcolemma

What is the synaptic cleft? A. the space between the synaptic terminal and the motor end plate B. the region of the neuron containing synaptic vesicles C. the step where acetylcholinesterase (AChE) breaks down, or cleaves, acetylcholine D. the border between the motor end plate and the sarcolemma

A. the space between the synaptic terminal and the motor end plate

T tubules and the terminal cisternae are clustered into structures called __________. A. triads B. fascicles C. myofibrils D. sarcomeres

A. triads

When the sarcomere is at rest, what is covering the active sites on actin? A. tropomyosin B. cross-bridges C. myosin D. troponin

A. tropomysosin

To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers? A. troponin B. myosin C. actin D. tropomyosin

A. troponin

What component of the thin filament binds to calcium once calcium is released from the terminal cisternae of the sarcoplasmic reticulum? A. troponin B. actin C. myosin D. tropomyosin

A. troponin

When calcium is released inside a muscle cell, what does it bind to? A. troponin B. myosin C. actin D. tropomyosin

A. troposin

The post-synaptic reaction on the sarcolemma is short in duration. Which of the following explanations describes why the reaction of the sarcolemma is short in duration? SELECT ALL A. Muscle tissue has a smaller membrane potential than nervous tissue. B. ACh diffuses out of the synaptic cleft. C. AChE acts to breakdown the ACh in the synaptic cleft. D. ACh diffuses across the synaptic cleft toward the sarcolemma. E. The ACh receptors respond only for a short period of time.

B. ACh diffuses out of the synaptic cleft. C. AChE acts to breakdown the ACh in the synaptic cleft.

The characteristic muscle stiffness associated with rigor mortis is due to the inability of myosin filaments to detach from the active site on actin filaments. What molecule is essential for this detachment? A. acetylcholinesterase B. ATP C. acetylcholine D. calcium

B. ATP

Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine? A. Acetylcholine is transported back into the axon terminal by a reuptake mechanism. B. Acetylcholine is degraded by acetylcholinesterase. C. Acetylcholine is transported into the postsynaptic neuron by receptor-mediated endocytosis. D. Acetylcholine diffuses away from the cleft.

B. Acetylcholine is degraded by acetylcholinesterase.

When does cross bridge cycling end? A. Cross bridge cycling ends when ATP binds to the myosin head. B. Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin. C. Cross bridge cycling ends when calcium release channels in the sarcoplasmic reticulum open. D. Cross bridge cycling ends when calcium ions are passively transported back into the sarcoplasmic reticulum.

B. Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.

Myasthenia gravis is an autoimmune disorder that results in the production of antibodies that either block or cause the destruction of the ACh receptor. Why do you think that Tamara's symptoms become worse as the day progresses? A. As the muscle becomes fatigued over the course of the day's activities, the receptors bind less acetylcholine, which results in smaller and smaller action potentials being generated. Smaller action potentials mean weaker contractions, as seen by the increasing muscle weakness. B. In the morning, the neuronal reserves of acetylcholine are larger, allowing for sufficient neurotransmitter release and resulting in effective muscle signaling. As the day progresses and the stores of acetylcholine become depleted, muscle function becomes progressively worse. C. In the morning, the reserves of ATP are larger, allowing for sufficient acetylcholine release to overcome the unresponsive receptors. However, as the day progresses and stores of ATP become depleted, muscle function becomes progressively worse. D. In myasthenia gravis the ACh receptors have a hyper affinity to acetylcholine. After muscle activity, fatigue and weakness occur as fewer unbound receptors are available to bind acetylcholine.

B. In the morning, the neuronal reserves of acetylcholine are larger, allowing for sufficient neurotransmitter release and resulting in effective muscle signaling. As the day progresses and the stores of acetylcholine become depleted, muscle function becomes progressively worse.

What happens immediately after the myosin head binds to the active site on actin? A. The myosin head detaches from the active site on actin. B. The myosin head pivots, moving the actin strand. C. Tropomyosin moves away from the active site on actin. D. ATP binds to the myosin head.

B. The myosin head pivots, moving the actin strand.

During neuromuscular transmission, the axon terminals release __________. A calcium ions B acetylcholine C sodium ions D acetylcholinesterase

B. acetylcholine

Which of the following proteins contains the active site involved in cross-bridge formation? A. troponin B. actin C. myosin D. tropomyosin

B. actin

ATP binding leads to which of the following actions? A. cross-bridge formation B. detaching and resetting cross-bridges C. exposure of active sites on actin D. pivoting of the myosin head

B. detaching and reseting cross-bridges

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft? A. a protein carrier B. exocytosis C. a channel

B. exocytosis

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. transverse or T tubules

Which of the following is/are mechanism(s) to end neural transmission at the neuromuscular junction? SELECT ALL THAT ARE CORRECT A. ACh is taken up by the axon terminal via endocytosis. B. ACh binds to ACh receptors. C. ACh diffuses away from the synaptic cleft. D. ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE).

C. ACh diffuses away from the synaptic cleft. D. ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE).

Tamara's muscle weakness and fatigue becomes progressively worse over the course of the day. This is a hallmark sign of myasthenia gravis, an autoimmune disorder that affects the ability of a motor neuron to communicate with a muscle fiber. What synaptic events must happen first for excitation to occur? A. The action potential travels down the T tubules in the sarcolemma and triggers the release of calcium ions from the sarcoplasmic reticulum. B. Calcium binds to tropomyosin, shifting it from the active site on actin, allowing cross bridge formation to occur as myosin binds to the active site. C. Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate. D. Sodium ions from the extracellular fluid diffuse into the cytosol of the muscle fiber, triggering the generation of an action potential in the sarcolemma.

C. Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate.

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

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

What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated? A. A motor neuron typically innervates only one skeletal muscle fiber. B. Motor neurons always innervate thousands of skeletal muscle fibers. C. Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. D. A skeletal muscle fiber is innervated by multiple motor neurons.

C. Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.

Myosin molecules form cross-bridges when they attach to __________. A. calcium B. tropomyosin C. actin D. troponin

C. actin

The sarcoplasmic reticulum contains __________. A. troponin B. myofilaments C. calcium D. T tubules

C. calcium

Inside a muscle, bundles of single muscle fibers form __________. A. T tubules B. sarcomeres C. fascicles D. thick filaments

C. fascicles

Acetylcholine receptors are primarily located __________. A. inside the muscle fiber B. inside vesicles C. on the motor end plate D. on the synaptic terminal

C. on the motor end plate

The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________. A. synaptic cleft B. motor end plate C. synaptic terminal D. acetylcholine receptor

C. synaptic terminal

An action potential in the muscle fiber causes __________. A. acetylcholinesterase to break down acetylcholine B. acetylcholine to bind to receptors on the motor end plate C. the muscle fiber to contract D. the release of acetylcholine into the synaptic cleft

C. the muscle fiber to contract

Acetylcholine binds to its receptor in the sarcolemma and triggers __________. A. the opening of voltage-gated calcium channels B. the opening of ligand-gated anion channels C. the opening of ligand-gated cation channels D. the opening of calcium-release channels

C. the opening of ligand-gated cation channels

Myosin molecules form what part of the sarcomere? A. tropomyosin B. actin C. thick filament D. thin filament

C. thick filament

Which of the following causes the active site on actin to be exposed or uncovered? A. cross-bridge formation B. troponin releasing calcium C. tropomyosin shifting position D. calcium entering the sarcoplasmic reticulum

C. tropomyosin shifting position

Inside a neuron, acetylcholine is contained within __________. A. the synaptic cleft B. acetylcholine receptors C. vesicles D. the motor end plate

C. vesicles

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

D. A series of proteins that control calcium release.

After a power stroke, the myosin head must detach from actin before another power stroke can occur. 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. ATP binds to the myosin head.

The injection that dramatically improved Tamara's symptoms was Tensilon, an acetylcholinesterase inhibitor. What is acetylcholinesterase, and why was this injection effective in relieving Tamara's symptoms? A. Acetylcholinesterase is a regulatory enzyme that inhibits the ACh receptors on the motor end plate. Inhibiting acetylcholinesterase improves muscle function because the ACh receptors are temporarily more active. B. Acetylcholinesterase is an enzyme that degrades the ACh receptors. When acetylcholinesterase is inhibited, there are more receptors available for acetylcholine to bind, and muscle function improves. C. Acetylcholinesterase is an acetylcholine antagonist that binds to motor end plate receptors and decreases the permeability of the sarcolemma to sodium. Inhibiting acetylcholinesterase increases the influx of sodium, leading to the generation of action potentials and an improvement in muscle function. D. Acetylcholinesterase is the enzyme that clears acetylcholine from the synapse. Inhibiting this enzyme will enable acetylcholine to be available for a longer period to bind to receptors.

D. Acetylcholinesterase is the enzyme that clears acetylcholine from the synapse. Inhibiting this enzyme will enable acetylcholine to be available for a longer period to bind to receptors.

The cross bridge cycle starts when _________. A. Ca2+ from the sarcoplasmic reticulum binds to tropomyosin B. acetylcholine diffuses away from the synaptic cleft C. Ca2+ is actively transported into the sarcoplasmic reticulum D. Ca2+ from the sarcoplasmic reticulum binds to troponin E. ATP binds to troponin and is hydrolyzed to ADP and Pi

D. Ca2+ from the sarcoplasmic reticulum binds to troponin

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber? A. Calcium ions are stored in the transverse tubules. B. Calcium ions are stored in the nuclei. C. Calcium ions are stored in the mitochondria. D. Calcium ions are stored in the sarcoplasmic reticulum.

D. Calcium ions are stored in the sarcoplasmic reticulum.

In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm. A. motor-end plate B sarcomere C troponin molecules D sarcoplasmic reticulum

D. SR

The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by __________. A. myofibrils B. myofilaments C. the sarcoplasmic reticulum D. T tubules

D. T Tubules

How does the myosin head obtain the energy required for activation? A. The energy comes from oxidative phophorylation. B. The energy comes from the direct phosphorylation of ADP by creatine phosphate. C. The energy comes from the hydrolysis of GTP. D. The energy comes from the hydrolysis of ATP.

D. The energy comes from the hydrolysis of ATP.

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why? A. The outside surface of the sarcolemma is negatively charged compared to the inside surface. Sodium ions diffuse outward along favorable chemical and electrical gradients. B. The inside surface of the sarcolemma is negatively charged compared to the outside surface. Potassium ions diffuse inward along favorable chemical and electrical gradients. C. The outside surface of the sarcolemma is negatively charged compared to the inside surface. Potassium ions diffuse outward along favorable chemical and electrical gradients. D. The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.

D. The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.

Which of the following statements is true? A. Acetylcholinesterase (AChE) is stored in vesicles within the presynaptic motor neuron. B. The acetylcholine (ACh) receptors are located on the myofibril membrane. C. The sarcolemma is the presynaptic membrane. D. The neurotransmitter is stored in the presynaptic motor neuron.

D. The neurotransmitter is stored in the presynaptic motor neuron.

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter? A. dopamine B. norepinephrine C. serotonin D. acetylcholine (ACh)

D. acetylcholine

In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases A sodium ions. B hydrogen ions. C potassium ions. D calcium ions. E acetylcholine.

D. calcium ions

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. extend from the brain to the sarcolemma of a skeletal muscle fiber C. arise in the epimysium of a skeletal muscle and extend to individual skeletal muscle fibers D. extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

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

Myofibrils are __________. A. connections between actin and myosin B. proteins that cover active sites on actin C. bundles of muscle cells inside a whole muscle D. made of a series of sarcomeres

D. made of a series of sarcomeres

The neuromuscular junction is a connection between a neuron and a __________. A. vesicle B. myofibril C. synaptic terminal D. muscle fiber

D. muscle fiber

What area of the thick filament binds to actin once its active binding sites are exposed? A. troponin B. tropomyosin C. hinge D. myosin cross-bridge (head)

D. myosin cross-bridge

The role of acetylcholinesterase in the neuromuscular junction is to __________. A. increase the sodium permeability of the motor end plate B. release acetylcholine from the synaptic terminal C. generate a muscle action potential D. remove acetylcholine from the synaptic cleft

D. remove acetylcholine from the synaptic cleft

Z lines define the edges of which of the following? A. cross-bridges B. myofibrils C. myosin D. sarcomeres

D. sarcomeres

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? A. cytosol B. T tubule C. sarcolemma D. terminal cisternae of the sarcoplasmic reticulum

D. terminal cisternae of the sarcoplasmic reticulum

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

D. through calcium release from the sarcoplasmic reticulum

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open? A. chemically gated calcium channels B. voltage-gated potassium channels C. voltage-gated sodium channels D. voltage-gated calcium channels

D. voltage-gated calcium channels

Which of the following events most directly occurs due to an action potential generated by the motor neuron? A. AChE breaks down ACh in the synaptic cleft. B. ACh binds to ACh receptors. C. Na rushes into the sarcolemma. D. An action potential is generated on the muscle fiber. E. ACh is released at the synapse.

E. ACh is released at the synapse.

Cross bridge detachment is caused by ________ binding to the myosin head. a ATP b acetylcholine c calcium d acetylcholinesterase e magnesium

a ATP

How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle? a It would cause muscles to stay contracted. b It would make the muscles less excitable. c It would cause muscles to stay relaxed. d It would produce muscle weakness. e It would have little effect on skeletal muscles.

a It would cause muscles to stay contracted.

Why do the disease tetanus and the normal sustained muscle contraction called tetanus share the same name? a They both eliminate the relaxation phase in the affected muscle fibers. b They both enable muscle fibers to reach near maximum tension. c They are both brought on by bacterial infections. d All of the above.

a They both eliminate the relaxation phase in the affected muscle fibers.

A myosin head binds to which molecule to form a cross bridge? a actin b tropomyosin c troponin

a actin

Fatigued muscles signify __________. a decreased pH b lowered body temperature c accumulation of pyruvic acid d oxygen recovery

a decreased pH

In the liver, during the Cori cycle, a glucose is produced from lactic acid. b lactic acid is shuffled to muscle cells. c lactic acid is produced from pyruvic acid. d glucose is released from glycogen. e lactic acid is produced from glucose.

a glucose is produced from lactic acid

Receptors for acetylcholine are located on the a motor end plate. b synaptic knob. c synaptic cleft. d sarcomere. e transverse tubule

a motor end plate

The binding of calcium to which molecule causes the myosin binding sites to be exposed? a troponin b actin c myosin d tropomyosin

a troponin

Which of the following processes produces 36 ATP? a glycolysis b Krebs cycle and oxidative phosphorylation c hydrolysis of creatine phosphate

b Krebs cycle and oxidative phosphorylation

Each skeletal muscle fiber is controlled by a motor neuron at a single a transverse tubule. b neuromuscular junction. c sarcomere. d synaptic knob. e synaptic cleft.

b NMJ

The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________. a Oxygen rebinds to myoglobin. b Pyruvic acid is converted back to lactic acid. c Glycogen is synthesized from glucose molecules. d ATP is used to rephosphorylate creatine into creatine phosphate.

b Pyruvic acid is converted back to lactic acid.

Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products? a hydrolysis of creatine phosphate b glycolysis c Krebs cycle and oxidative phosphorylation

b glycolysis

The muscle weakness of myasthenia gravis results from a excessive acetylcholinesterase that destroys the neurotransmitter. b loss of acetylcholine receptors in the end-plate membrane. c insufficient acetylcholine release from presynaptic vesicles. d the motor neuron action potential being too small to stimulate the muscle fibers. e inability of the muscle fiber to produce ATP.

b loss of acetylcholine receptors in the end-plate membrane.

A muscle produces its highest tension when in complete a aerobic metabolism. b tetanus. c wave summation. d treppe. e recovery.

b tetanus

Which of the following acts as an ATPase during the contraction cycle of muscle? a the tail portion of the myosin molecule b the head portion of the myosin molecule c tropomyosin molecules d troponin molecules e actin molecules

b the head portion of the myosin molecule

A single contraction-relaxation cycle in a muscle fiber produces a(n) a tetanic contraction. b twitch. c action potential. d motor unit. e cramp.

b twitch

Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP? a red slow twitch fibers b white fast twitch fibers

b white fast twitch this sucks like alike so restless rn 104 copy and pastes.....

When acetylcholine binds to receptors at the motor end plate, the sarcolemma becomes a more permeable to calcium ions. b more permeable to sodium ions. c less permeable to sodium ions. d less permeable to potassium ions. e less permeable to potassium and sodium ions.

b. more permeable to sodium ions

Which of the following is important to increasing efficiency in tension production? a increasing calcium reclamation b increasing the latent period c a shortened relaxation phase d lengthening the zone of overlap

c a shortened relaxation phase

Triggering of the muscle action potential occurs after a acetylcholinesterase is released from synaptic vesicles into the synaptic cleft. b the action potential jumps across the neuromuscular junction. c acetylcholine binds to chemically-gated channels in the motor end plate. d calcium ion binds to channels on the motor end plate. e Any of these can produce an action potential in the muscle cell.

c acetylcholine binds to chemically-gated channels in the motor end plate.

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell? a troponin b ATP c arrival of an action potential d calcium ion pump

c arrival of an action potential

Active sites on the actin become available for binding after a troponin binds to tropomyosin. b calcium binds to tropomyosin. c calcium binds to troponin. d actin binds to troponin. e myosin binds to troponin.

c calcium binds to troponin

What is the type of chemical reaction used to rebuild ADP into ATP? a hydrolysis b rehydration synthesis c dehydration synthesis

c dehydration synthesis

The type of contraction in which the muscle fibers do not shorten is called a isotonic. b treppe. c isometric. d tetany. e concentric.

c isometric

Bacteria that cause tetanus release a neurotoxin called tetanospasmin. Which of the following components of the neuromuscular junction (NMJ) does this neurotoxin affect directly? a epimysium b myofilaments c motor neurons d sarcolemma

c motor neurons

A single motor neuron together with all the muscle fibers it innervates is called a(n) a myotome. b end foot. c motor unit. d dermatome. e end plate.

c motor unit

You try to pick up an object and discover that it is much heavier than you expected. Which process must occur in the muscle to increase tension so you can pick up the object? a complete tetanus b treppe c recruitment d isotonic contraction e wave summation

c recruitment

What causes the myosin head to disconnect from actin? a binding of calcium b binding of troponin c hydrolysis of ATP d binding of ATP

d binding of ATP

In which of the following would the motor units have the fewest muscle fibers? a postural muscles of the back b calf muscles c thigh muscles d muscles that control the eyes e muscles of the neck

d muscles that control the eyes

What causes the power stroke? a hydrolysis of ATP b binding of ATP c calcium d release of ADP and Pi

d release of ADP and Pi

The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter a antidiuretic hormone. b adrenaline. c epinephrine. d norepinephrine. e acetylcholine.

e acetylcholine

The most important factor in decreasing the intracellular concentration of calcium ion after contraction is a diffusion of calcium out of the cell. b active transport of calcium into the synaptic cleft. c diffusion of calcium into the sarcoplasmic reticulum. d active transport of calcium across the sarcolemma. e active transport of calcium into the sarcoplasmic reticulum.

e active transport of calcium into the SR

Physical evidence that supports the sliding filament theory of muscle contraction includes a constant distance between Z lines during contraction. b decreased width of the A band during contraction. c increased width of the I band during contraction. d the I band + H band distance is constant during contraction. e decreased width of the H band during contraction.

e decreased width of the H band during contraction.

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

e incomplete tetanus

In an isotonic contraction, a many twitches always fuse into one. b postural muscles stabilize the vertebrae. c the peak tension is less than the load. d tension rises and falls but the muscle length is constant. e muscle tension exceeds the load and the muscle lifts the load.

e muscle tension exceeds the load and the muscle lifts the load.

The action potential is conducted into a skeletal muscle fiber by a triads. b motor end plates. c sarcoplasmic reticulum. d neuromuscular junctions. e transverse tubules.

e transverse tubules

When calcium ion binds to troponin, a myosin shortens. b active sites on the myosin are exposed. c actin heads will bind to myosin. d muscle relaxation occurs. e tropomyosin rolls away from the active site.

e tropomyosin rolls away from the active site.

In rigor mortis a ATP is depleted. b calcium ions keep binding to troponin. c the myosin heads are attached to actin. d sustained contractions occur. e All of the answers are correct.

e. all answers

The narrow space between the synaptic terminal and the muscle fiber is the a synaptic knob. b motor end plate. c M line. d motor unit. e synaptic cleft.

e. synaptic cleft