Question 1

Which of the following choices lists a correct sequence of events following the depolarization of transverse tubules in excitation-contraction coupling in cardiac muscle?

Accepted Answer

A)  calcium release into cytosol,calcium ion influx through sarcolemma,actin and myosin attach,thin filaments slide toward the middle of sarcomeres
B)  actin and myosin attach,thin filaments slide toward the middle of sarcomeres,calcium release into cytosol
C)  calcium release into cytosol,actin and myosin attach,calcium ion influx through sarcolemma,thin myofilaments slide toward the middle of sarcomeres
D)  calcium release into cytosol,actin and myosin attach,thin filaments slide toward the middle of sarcomeres,calcium ion influx through sarcolemma
E)  calcium ion influx through sarcolemma,calcium release into cytosol,actin and myosin attach,thin myofilaments slide toward the middle of sarcomeresF) A) and C)
G) A) and B)

Question 2

Skeletal muscles are made up of bundles of muscle fibers attached to bone by connective-tissue called tendons.

Accepted Answer

A) True 
 B)False

Question 3

What is the function of the transverse tubules in a skeletal-muscle fiber?

Accepted Answer

A)  They store the calcium ions that are the main source of activation for the cross-bridge cycle.
B)  They form the Z lines that mark the end of each sarcomere.
C)  They allow action potentials to propagate deep into the center of skeletal muscle cells.
D)  They manufacture and store ATP.
E)  They run in parallel with the myofibrils,and have abundant Ca2+-ATPase proteins for pumping Ca2+ back into the sarcoplasmic reticulum.F) A) and C)
G) B) and D)

Question 4

In cardiac muscle cells the release of Ca2+ through L-type Ca2+ channels depolarizes the sarcoplasmic reticulum and inhibits the release of any additional Ca2+ necessary for excitation-contraction coupling.

Accepted Answer

A) True 
 B)False

Question 5

Endurance exercise,such as long-distance swimming,causes a preferential increase in glycolytic enzymes and increased mass of the exercising muscles.

Accepted Answer

A) True 
 B)False

Question 6

The larger the diameter of a skeletal-muscle fiber,the greater the tension it can generate.

Accepted Answer

A) True 
 B)False

Question 7

In the first few seconds of skeletal muscle contraction,what is the main mechanism by which ATP is replenished?

Accepted Answer

A)  Energy and phosphate are transferred from creatine phosphate to ADP.
B)  Oxidative phosphorylation rapidly generates ATP from glucose.
C)  Glycolysis produces ATP from glycogen.
D)  Oxidation of fatty acids into ATP occurs in the mitochondria.
E)  Myoglobin catalysis produces ATP.F) A) and C)
G) A) and D)

Question 8

Which membrane protein transport process plays an important role in terminating the contraction of cardiac muscle?

Accepted Answer

A)  Ca 2+-ATPase pumps move Ca2+ from the T-tubule back into the sarcoplasmic reticulum.
B)  Na+/K+-ATPase pumps move Na+ back into the cytosol and K+ back into the T-tubule lumen.
C)  Ca2+-ATPase pumps move Ca2+ from the cytosol back into the sarcoplasmic reticulum.
D)  Na+/Ca2+-exchangers move Na+ out of the cytosol in exchange for Ca2+ movement into the sarcoplasmic reticulum.
E)  Na+/K+-ATPase pumps move Na+ and K+ back out of the cell.F) C) and E)
G) B) and C)

Question 9

The removal of calcium ions from the cytosol of skeletal muscle causes

Accepted Answer

A)   the myosin binding sites on actin to be uncovered by tropomyosin.
B)   tropomyosin to change conformation and thereby move troponin molecules over cross-bridge binding sites.
C)   troponin to change conformation and thereby expose cross-bridge binding sites.
D)   the myosin binding sites on actin to be covered by tropomyosin.
E)   None of the choices are correct.F) A) and B)
G) A) and C)

Question 10

Curare blocks neuromuscular transmission by preventing the release of neurotransmitters from the motor neuron.

Accepted Answer

A) True 
 B)False

Question 11

Compared to type I (slow oxidative) skeletal muscle fibers,how are type II b (fast-glycolytic) skeletal-muscle fibers different?

Accepted Answer

A)  Type II b fibers have more abundant mitochondria.
B)  Type II b fibers fatigue more readily.
C)  Type II b fibers have more abundant myoglobin.
D)  Type II b fibers are smaller in diameter.
E)  Type II b motor units contain fewer fibers per alpha motor neuron.F) B) and E)
G) A) and D)

Question 12

How does the chemical curare affect skeletal muscle function?

Accepted Answer

A)  It activates an autoimmune disease that destroys myelin.
B)  It blocks the action of acetylcholinesterase at the neuromuscular junction.
C)  It is a muscarinic acetylcholine receptor antagonist that blocks synaptic transmission at the neuromuscular junction.
D)  It is a nicotinic acetylcholine antagonist that blocks synaptic transmission at the neuromuscular junction.
E)  It locks ligand-gated channels in the open state,leading to spastic contractions of muscle.F) C) and D)
G) C) and E)

Question 13

Which best describes a role of L-type Ca2+ channels in cardiac muscle cells?

Accepted Answer

A)  They function exactly the same in cardiac muscle cells as they do in skeletal muscle.
B)  They are directly responsible for making cardiac muscle fatigue resistant.
C)  They are responsible for preventing tetanic contractions.
D)  They cause the absolute refractory period to be very brief.
E)  They act as non-conducting voltage sensors that mediate excitation-contraction coupling.F) A) and D)
G) B) and E)

Question 14

Abundant myoglobin is typical of which type of skeletal muscle fibers?

Accepted Answer

A)  Type I
B)  Type IIC) A) and B)
D) undefined

Question 15

Which type of skeletal muscle fiber typically has the fewest mitochondria?

Accepted Answer

A)  Type I
B)  Type IIC) A) and B)
D) undefined

Question 16

Abundant mitochondria is typical of which type of skeletal muscle fibers?

Accepted Answer

A)  Type I
B)  Type IIC) A) and B)
D) undefined

Question 17

The latent period of an isotonic twitch is shorter than the latent period of an isometric twitch.

Accepted Answer

A) True 
 B)False

Question 18

The phenomenon of rigor mortis demonstrates that myosin can remain bound to actin in the absence of additional ATP,but the bond cannot then be broken.

Accepted Answer

A) True 
 B)False

Question 19

The prolonged electrical depolarization of cardiac muscle cells that occurs during contraction is due primarily to the persistent influx of what ion?

Accepted Answer

A)  sodium
B)  calcium
C)  nitrate
D)  chloride
E)  potassiumF) B) and C)
G) A) and D)

Question 20

Binding of ________ to myosin permits cross-bridge _____________ between actin and myosin in skeletal muscle cells.

Accepted Answer

A)  ATP; attachment
B)  ATP; detachment
C)   calcium; attachment
D)   calcium; detachment
E)   actin; detachmentF) C) and E)
G) C) and D)

Exam 9: Muscle

In cardiac muscle cells the release of Ca2+ through L-type Ca2+ channels depolarizes the sarcoplasmic reticulum and inhibits the release of any additional Ca2+ necessary for excitation-contraction coupling.

Correct AnswerverifiedShow Answer

Abundant myoglobin is typical of which type of skeletal muscle fibers?

Correct AnswerverifiedShow Answer

Binding of ________ to myosin permits cross-bridge _____________ between actin and myosin in skeletal muscle cells.

Correct AnswerverifiedShow Answer

The latent period of an isotonic twitch is shorter than the latent period of an isometric twitch.

Correct AnswerverifiedShow Answer

Abundant mitochondria is typical of which type of skeletal muscle fibers?

Correct AnswerverifiedShow Answer

What is the function of the transverse tubules in a skeletal-muscle fiber?

Correct AnswerverifiedShow Answer

In the first few seconds of skeletal muscle contraction,what is the main mechanism by which ATP is replenished?

Correct AnswerverifiedShow Answer

The removal of calcium ions from the cytosol of skeletal muscle causes

Correct AnswerverifiedShow Answer

How does the chemical curare affect skeletal muscle function?

Correct AnswerverifiedShow Answer

Skeletal muscles are made up of bundles of muscle fibers attached to bone by connective-tissue called tendons.

Correct AnswerverifiedShow Answer

Which best describes a role of L-type Ca2+ channels in cardiac muscle cells?

Correct AnswerverifiedShow Answer

Which membrane protein transport process plays an important role in terminating the contraction of cardiac muscle?

Correct AnswerverifiedShow Answer

Compared to type I (slow oxidative) skeletal muscle fibers,how are type II b (fast-glycolytic) skeletal-muscle fibers different?

Correct AnswerverifiedShow Answer

The prolonged electrical depolarization of cardiac muscle cells that occurs during contraction is due primarily to the persistent influx of what ion?

Correct AnswerverifiedShow Answer

Which of the following choices lists a correct sequence of events following the depolarization of transverse tubules in excitation-contraction coupling in cardiac muscle?

Correct AnswerverifiedShow Answer

Which type of skeletal muscle fiber typically has the fewest mitochondria?

Correct AnswerverifiedShow Answer

The phenomenon of rigor mortis demonstrates that myosin can remain bound to actin in the absence of additional ATP,but the bond cannot then be broken.

Correct AnswerverifiedShow Answer

The larger the diameter of a skeletal-muscle fiber,the greater the tension it can generate.

Correct AnswerverifiedShow Answer

Curare blocks neuromuscular transmission by preventing the release of neurotransmitters from the motor neuron.

Correct AnswerverifiedShow Answer

Endurance exercise,such as long-distance swimming,causes a preferential increase in glycolytic enzymes and increased mass of the exercising muscles.

Correct AnswerverifiedShow Answer

In cardiac muscle cells the release of Ca²⁺ through L-type Ca²⁺ channels depolarizes the sarcoplasmic reticulum and inhibits the release of any additional Ca²⁺ necessary for excitation-contraction coupling.

Correct Answer
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Binding of to myosin permits cross-bridge _____ between actin and myosin in skeletal muscle cells.

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Which best describes a role of L-type Ca²⁺ channels in cardiac muscle cells?

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