Question 1

What protein is the principal component of skeletal muscle thick filaments?

Accepted Answer

A)   actin
B)   myosin
C)   troponin
D)   calmodulin
E)   tropomyosinF) A) and C)
G) A) and D)

Question 2

Which of the following statements regarding contraction of a skeletal muscle fiber is TRUE?

Accepted Answer

A)   Thick filaments shorten when muscle cells contract.
B)   Some contractions occur without cross-bridge activation.
C)   Contracting muscle fibers do not always shorten.
D)   Contraction does not always require the occurrence of an action potential.
E)   Contraction only occurs following summation of action potentials from many motor neurons.F) D) and E)
G) B) and C)

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 E)
G) A) and D)

Question 4

During isometric contraction of a skeletal muscle fiber, tension increases but the fiber length stays the same.

Accepted Answer

A) True 
 B)False

Question 5

Which of the following is FALSE regarding single-unit smooth muscle cells?

Accepted Answer

A)   They have an individual neuron innervating of each individual smooth-muscle cell.
B)   They have many gap junctions between cells.
C)   They may have pacemaker activity.
D)   They may respond to stretch by contracting.
E)   They exhibit tone.F) B) and D)
G) All of the above

Question 6

Organophosphate "nerve gases" induce paralysis by blocking neural stimulation of the neuromuscular junctions, while botulinum toxin produces the same effect by inhibiting acetylcholinesterase.

Accepted Answer

A) True 
 B)False

Question 7

Neuronal stimulation of skeletal muscle is always excitatory, whereas neuronal stimulation of smooth muscle may be excitatory or inhibitory.

Accepted Answer

A) True 
 B)False

Question 8

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

Accepted Answer

A) True 
 B)False

Question 9

The force-generating sites in a myofibril are the Z lines.

Accepted Answer

A) True 
 B)False

Question 10

John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest. Jim is a marathon runner who specializes in long, steady runs. Compared to John's muscles, how are Jim's most likely to differ?

Accepted Answer

A)   Jim's muscles will have more glycogen stored in his type IIb muscle fibers.
B)   Jim's muscles will have more mitochondria in his type I and IIa muscle fibers.
C)   Jim's muscles will have less myoglobin in his type I muscle fibers.
D)   Jim's type IIb fibers will be larger in diameter.
E)   Jim will have a greater proportion of type II muscle fibers and a lower proportion of type I fibers than John.F) C) and E)
G) B) and E)

Question 11

The site of Ca2+ storage in muscle cells is the lateral sacs of the transverse tubules.

Accepted Answer

A) True 
 B)False

Question 12

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 E)
G) B) and E)

Question 13

Multiunit smooth muscle cells

Accepted Answer

A)   generally have individual innervation of each cell.
B)   have many gap junctions between cells.
C)   respond to stretch by relaxing.
D)   can only be excited, and not inhibited.
E)   have abundant T-tubules.F) A) and B)
G) D) and E)

Question 14

Smooth muscle cells may contract in the absence of neuronal stimulation.

Accepted Answer

A) True 
 B)False

Question 15

How is the length of a skeletal muscle cell related to the force it can generate?

Accepted Answer

A)   The tension in a skeletal muscle cell is greatest when contractions occur at either very short or very long lengths.
B)   Skeletal muscle cells generate the same amount of force, regardless of their length.
C)   The shorter a skeletal muscle cell is when it begins to contract, the stronger the force generation will be.
D)   The longer a skeletal muscle cell is when it begins to contract, the stronger the force generation will be.
E)   Skeletal muscle cells generate the most force when the contraction occurs at an intermediate length.F) A) and B)
G) All of the above

Question 16

During skeletal muscle contraction, the distance between the Z lines of a sarcomere decreases because of shortening of the thick and thin filaments.

Accepted Answer

A) True 
 B)False

Question 17

Fast myosin ATPase activity is typical of which type of skeletal muscle fibers?

Accepted Answer

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

Question 18

If a biopsy of the quadriceps (thigh extensor)  muscles were taken from gold medal-winning speed skaters in the 4 events below, which would most likely have the SMALLEST percentage of type I muscle fibers?

Accepted Answer

A)   10,000 meters
B)   5,000 meters
C)   1,000 meters
D)   500 metersE) None of the above
F) B) and D)

Question 19

Which of these is a major difference between smooth muscle and skeletal muscle?

Accepted Answer

A)   Myosin is the main regulatory protein in smooth muscle.
B)   Myosin is the main regulatory protein in skeletal muscle.
C)   Skeletal muscle usually exhibits spontaneous activity, while smooth muscle cannot contract spontaneously.
D)   Only skeletal muscle requires increased calcium ion concentration in the cytosol for contraction.
E)   Only skeletal muscle has both actin and myosin.F) B) and E)
G) A) and C)

Question 20

Which type of skeletal muscle fibers is generally recruited first?

Accepted Answer

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

Exam 9: Muscle

The site of Ca2+ storage in muscle cells is the lateral sacs of the transverse tubules.

Correct AnswerverifiedShow Answer

The force-generating sites in a myofibril are the Z lines.

Correct AnswerverifiedShow Answer

John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest. Jim is a marathon runner who specializes in long, steady runs. Compared to John's muscles, how are Jim's most likely to differ?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which of the following is FALSE regarding single-unit smooth muscle cells?

Correct AnswerverifiedShow Answer

Organophosphate "nerve gases" induce paralysis by blocking neural stimulation of the neuromuscular junctions, while botulinum toxin produces the same effect by inhibiting acetylcholinesterase.

Correct AnswerverifiedShow Answer

Which type of skeletal muscle fibers is generally recruited first?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which of the following statements regarding contraction of a skeletal muscle fiber is TRUE?

Correct AnswerverifiedShow Answer

How is the length of a skeletal muscle cell related to the force it can generate?

Correct AnswerverifiedShow Answer

During skeletal muscle contraction, the distance between the Z lines of a sarcomere decreases because of shortening of the thick and thin filaments.

Correct AnswerverifiedShow Answer

Smooth muscle cells may contract in the absence of neuronal stimulation.

Correct AnswerverifiedShow Answer

If a biopsy of the quadriceps (thigh extensor) muscles were taken from gold medal-winning speed skaters in the 4 events below, which would most likely have the SMALLEST percentage of type I muscle fibers?

Correct AnswerverifiedShow Answer

Neuronal stimulation of skeletal muscle is always excitatory, whereas neuronal stimulation of smooth muscle may be excitatory or inhibitory.

Correct AnswerverifiedShow Answer

Fast myosin ATPase activity is typical of which type of skeletal muscle fibers?

Correct AnswerverifiedShow Answer

Multiunit smooth muscle cells

Correct AnswerverifiedShow Answer

During isometric contraction of a skeletal muscle fiber, tension increases but the fiber length stays the same.

Correct AnswerverifiedShow Answer

What protein is the principal component of skeletal muscle thick filaments?

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 of these is a major difference between smooth muscle and skeletal muscle?

Correct AnswerverifiedShow Answer

The site of Ca²⁺ storage in muscle cells is the lateral sacs of the transverse tubules.

Correct Answer
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