Question 1

Describe two mechanisms by which the human nervous system can voluntarily alter the force and velocity of a contraction of the biceps muscle of the arm.

Accepted Answer

1. Varying numbers of motor un...

Question 2

In resting skeletal muscle, contraction does not occur because

Accepted Answer

A)   there is very little ATP in the cytoplasm.
B)   most of the ATP is bound to other molecules for storage.
C)   there is very little calcium in the cytoplasm.
D)   myosin is inactivated.

Question 3

During an eccentric muscle contraction, the

Accepted Answer

A)   length of the sarcomeres remains unchanged, but the length of the elastic component increases.
B)   sarcomeres shorten, but the length of the elastic component remains unchanged.
C)   muscle produces force and its length decreases.
D)   muscle produces force and its length increases.

Question 4

The small diameter of slow oxidative muscle fibers is particularly advantageous for minimizing the distance over which

Accepted Answer

A)   calcium diffuses from the sarcolemma to the myofibrils.
B)   oxygen diffuses from the sarcolemma to the mitochondria.
C)   glycogen diffuses from the sarcolemma to the myofibrils.
D)   lactate diffuses from the myofibrils to the sarcolemma.

Question 5

Why does a skeletal muscle twitch last longer than a skeletal muscle action potential?

Accepted Answer

The twitch begins with the action potent...

Question 6

According to the sliding filament theory of muscle contraction, myosin heads pull on _______ filaments and _______.

Accepted Answer

A)   thick; move the Z discs apart
B)   thick; move the Z discs together
C)   thin; move the Z discs apart
D)   thin; move the Z discs together

Question 7

The diffusion rate of which factor best explains why vertebrates evolved to have slow oxidative muscle fibers that are smaller in diameter than fast glycolytic fibers?

Accepted Answer

A)   Lipid
B)   Oxygen
C)   Ca2+
D)   Glucose

Question 8

A muscle produces less force during a twitch than during a tetanic contraction because during a twitch

Accepted Answer

A)   peak cytoplasmic Ca2+ is lower.
B)   tropomyosin does not have time to unblock all of the actomyosin binding sites.
C)   myosin does not have time to bind to as many actin molecules.
D)   the elastic components of the muscle are not fully stretched.

Question 9

One reason that fast glycolytic muscle fibers fatigue more rapidly than slow oxidative muscle fibers is that fast glycolytic fibers

Accepted Answer

A)   contain lower amounts of ATP than slow oxidative fibers.
B)   have a lower capacity for glycolysis than slow oxidative fibers.
C)   have a higher capacity for oxidative phosphorylation than slow oxidative fibers.
D)   use ATP more rapidly than slow oxidative fibers.

Question 10

In striated muscle, _______ before the sarcomere can generate force.

Accepted Answer

A)   Ca2+ must dissociate from troponin C
B)   Ca2+ must be pumped by the SR Ca2+-ATPase
C)   the SR calcium channel must open
D)   calcium must bind to tropomyosin

Question 11

How can summation of skeletal muscle twitches occur if the motor neuron's refractory period prevents multiple action potentials from being transmitted to the neuromuscular junction at the same time?

Accepted Answer

A)   The motor neuron's absolute refractory period is much shorter than the time it takes for calcium release and reuptake from the SR.
B)   The motor neuron's absolute refractory period is much longer than the time it takes for calcium release and reuptake from the SR.
C)   The motor neuron's absolute refractory period is much shorter than the muscle action potential.
D)   The motor neuron's absolute refractory period is much longer than the muscle action potential.

Question 12

During the latent period of an isometric twitch,

Accepted Answer

A)   myosin hydrolyzes ATP and releases from actin.
B)   Ca2+ binds to troponin C.
C)   ryanodine receptors open and conduct Ca2+ into the SR.
D)   tropomyosin moves to block myosin-binding sites on actin.

Question 13

Refer to the figure shown.
 In the figure, which numeral represents the A band?

Accepted Answer

A)   I
B)   II
C)   III
D)   IV

Question 14

Identify the two major uses of ATP in skeletal muscle cells that are involved in contraction and relaxation and explain why each process uses ATP more rapidly in fast-twitch muscles than in slow-twitch muscles.

Accepted Answer

Myosin hydrolyzes ATP as part of the cro...

Question 15

Refer to the figure shown.
 Which area(s)  shorten(s)  during muscle contraction?

Accepted Answer

A)   I
B)   III
C)   I and III
D)   III and V

Question 16

During an isometric tetanic contraction, the sarcomeres

Accepted Answer

A)   shorten, but the elastic components lengthen.
B)   shorten, but the elastic components stay the same length.
C)   and the elastic components shorten.
D)   lengthen, but the elastic components shorten.

Question 17

Mammalian cardiac muscle cells are stimulated to contract by

Accepted Answer

A)   hormonal signals that trigger Ca2+ release and myosin light-chain phosphorylation.
B)   electrical signals transmitted through gap junctions from other autorhythmic cardiac muscle cells.
C)   action potentials from excitatory autonomic neurons.
D)   ion channels that open in response to stretch of the cardiac muscle cell membranes.

Question 18

Which statement is true of most arthropod and vertebrate skeletal muscle?

Accepted Answer

A)   Muscle fibers are innervated by multiple neurons.
B)   Muscle fibers receive both EPSPs and IPSPs.
C)   Different myosin isoforms in adjacent fibers produce different maximum shortening velocities.
D)   Ca2+ is released from the sarcoplasmic reticulum in response to depolarization of the fiber.

Question 19

Refer to the figure shown.
 In the figure, which panel, taken out of context, represents a state where muscle relaxation could be occurring?

Accepted Answer

A)   I
B)   II
C)   IV
D)   VI

Question 20

Refer to the figure shown.
 Which number on the diagram represents the most optimal positioning of actin and myosin before contraction?

Accepted Answer

A)   I
B)   II
C)   III
D)   IV

Exam 20: Muscle

Describe two mechanisms by which the human nervous system can voluntarily alter the force and velocity of a contraction of the biceps muscle of the arm.

Correct Answerverified1. Varying numbers of motor un...View AnswerShow Answer

A muscle produces less force during a twitch than during a tetanic contraction because during a twitch

Correct AnswerverifiedShow Answer

Mammalian cardiac muscle cells are stimulated to contract by

Correct AnswerverifiedShow Answer

According to the sliding filament theory of muscle contraction, myosin heads pull on _______ filaments and _______.

Correct AnswerverifiedShow Answer

Refer to the figure shown. Which area(s) shorten(s) during muscle contraction?

Correct AnswerverifiedShow Answer

Refer to the figure shown. In the figure, which numeral represents the A band?

Correct AnswerverifiedShow Answer

How can summation of skeletal muscle twitches occur if the motor neuron's refractory period prevents multiple action potentials from being transmitted to the neuromuscular junction at the same time?

Correct AnswerverifiedShow Answer

One reason that fast glycolytic muscle fibers fatigue more rapidly than slow oxidative muscle fibers is that fast glycolytic fibers

Correct AnswerverifiedShow Answer

The small diameter of slow oxidative muscle fibers is particularly advantageous for minimizing the distance over which

Correct AnswerverifiedShow Answer

In striated muscle, _______ before the sarcomere can generate force.

Correct AnswerverifiedShow Answer

During the latent period of an isometric twitch,

Correct AnswerverifiedShow Answer

Which statement is true of most arthropod and vertebrate skeletal muscle?

Correct AnswerverifiedShow Answer

Why does a skeletal muscle twitch last longer than a skeletal muscle action potential?

Correct AnswerverifiedThe twitch begins with the action potent...View AnswerShow Answer

Refer to the figure shown. In the figure, which panel, taken out of context, represents a state where muscle relaxation could be occurring?

Correct AnswerverifiedShow Answer

During an isometric tetanic contraction, the sarcomeres

Correct AnswerverifiedShow Answer

Refer to the figure shown. Which number on the diagram represents the most optimal positioning of actin and myosin before contraction?

Correct AnswerverifiedShow Answer

During an eccentric muscle contraction, the

Correct AnswerverifiedShow Answer

Identify the two major uses of ATP in skeletal muscle cells that are involved in contraction and relaxation and explain why each process uses ATP more rapidly in fast-twitch muscles than in slow-twitch muscles.

Correct AnswerverifiedMyosin hydrolyzes ATP as part of the cro...View AnswerShow Answer

In resting skeletal muscle, contraction does not occur because

Correct AnswerverifiedShow Answer

The diffusion rate of which factor best explains why vertebrates evolved to have slow oxidative muscle fibers that are smaller in diameter than fast glycolytic fibers?

Correct AnswerverifiedShow Answer

Correct Answer
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1. Varying numbers of motor un...
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Correct Answer
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According to the sliding filament theory of muscle contraction, myosin heads pull on _ filaments and _.

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The twitch begins with the action potent...
View Answer

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Myosin hydrolyzes ATP as part of the cro...
View Answer

Correct Answer
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Correct Answer
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