Question 1

Which is a TRUE statement about smooth muscle?

Accepted Answer

A)   Smooth muscle is striated.
B)   Smooth muscle does not have thick and thin filaments.
C)   Smooth muscle does not use troponin-tropomyosin to regulate cross-bridge activity.
D)   Changes in cytosolic calcium do not regulate cross-bridge activity in smooth muscle.
E)   The myosin in smooth muscle requires phosphorylation before it can bind to ATP.

Question 2

In general, activating a slow-oxidative motor unit in a muscle will generate more tension than activating a fast-glycolytic motor unit.

Accepted Answer

A) True 
 B)False

Question 3

The step of the cross-bridge cycle that immediately follows the attachment of ATP to the myosin head is referred to as the "powerstroke."

Accepted Answer

A) True 
 B)False

Question 4

Which of these occurs during an isometric contraction of a skeletal muscle?

Accepted Answer

A)   The I bands shorten and the A bands stay the same length.
B)   The thick and thin filaments slide past each other.
C)   Sarcomere length does not change significantly.
D)   The A bands shorten and the I bands stay the same length.
E)   Cross-bridges lock onto actin, similar to what occurs in rigor mortis. C

Question 5

What is the definition of a "motor unit"?

Accepted Answer

A)   a single motor neuron plus all the muscle fibers it innervates
B)   a single muscle fiber plus all of the motor neurons that innervate it
C)   all of the motor neurons supplying a single muscle
D)   a pair of antagonistic muscles
E)   all of the muscles that affect the movement of any given joint

Question 6

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; detachment

Question 7

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

Accepted Answer

A)   Type I
B)   Type II

Question 8

During concentric contractions of skeletal muscle, the I band and H zone shorten but the A band stays the same.

Accepted Answer

A) True 
 B)False

Question 9

Characteristics of slow-oxidative fibers include numerous mitochondria, abundant myoglobin, and large stores of glycogen.

Accepted Answer

A) True 
 B)False

Question 10

Which of the following statements about different kinds of skeletal muscle fibers is TRUE?

Accepted Answer

A)   Slow-oxidative fibers have a greater abundance of glycogen than do fast-glycolytic fibers.
B)   Fast-glycolytic fibers have a greater abundance of myoglobin than do slow-oxidative fibers.
C)   A fast-glycolytic fiber can generate greater tension than a slow-oxidative fiber.
D)   Fast-glycolytic fibers and slow-oxidative fibers are innervated by alpha motor neurons of the same diameter.
E)   To generate ATP, fast-glycolytic fibers depend mainly on oxidative phosphorylation while slow-oxidative fibers depend mainly on glycolysis.

Question 11

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

Accepted Answer

A)   Only one cross-bridge cycle can occur when the [Ca2+] is elevated in the cytosol; in order to undergo a second cycle, [Ca2+] must be sequestered in the sarcoplasmic reticulum and released again.
B)   ATP hydrolysis products must be removed from myosin before it can bind to actin.
C)   Binding of myosin to actin takes place when [Ca2+] increases in the cytosol.
D)   A single twitch in skeletal muscle lasts the same length of time as the action potential that causes it.
E)   The powerstroke of the cross-bridge cycle occurs simultaneously with ATP being hydrolyzed into ADP and Pi.

Question 12

A large diameter is typical of which type of skeletal muscle fibers?

Accepted Answer

A)   Type I
B)   Type II

Question 13

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

Accepted Answer

A) True 
 B)False

Question 14

Binding of myosin to actin in skeletal muscle cells does not normally take place in the absence of Ca2+.

Accepted Answer

A) True 
 B)False  True

Question 15

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 Jim, John is likely to have:

Accepted Answer

A)   legs with a larger diameter.
B)   legs with a smaller diameter.
C)   hypertrophy of type I muscle fibers.
D)   a higher density of capillaries in his legs.
E)   lower concentrations of glycolytic enzymes in his leg muscles.

Question 16

Why does breathing continue to be rapid and deep for a time after heavy exercise?

Accepted Answer

A)   Extra oxygen is needed to eliminate lactic acid and restore muscle creatine phosphate and glucose concentrations.
B)   The respiratory system is slow to increase and decrease its function before and after exercise, which is why it takes awhile for breathing to slow down.
C)   Lactic acid that builds up during heavy exercise must be exhaled into the air, so heavy breathing must continue for awhile after exercise to eliminate it.
D)   The ATP level in muscle cells falls drastically during heavy exercise, and extra oxygen is needed to restore it.
E)   The extra ventilation is not needed to replenish energy stores in muscle fibers, but rather simply to restore the blood pH to normal after the production of excess lactic acid during the exercise.

Question 17

Which type of skeletal muscle fibers fatigues most quickly?

Accepted Answer

A)   Type I
B)   Type II

Question 18

Fast fibers can be distinguished from slow fibers by the rate at which their myosin-ATPases split ATP.

Accepted Answer

A) True 
 B)False

Question 19

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

Accepted Answer

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

Question 20

Which is a TRUE statement about excitation-contraction coupling?

Accepted Answer

A)   In skeletal muscle cells, it requires the influx of extracellular calcium ion.
B)   In smooth muscle cells, it must be preceded by an action potential in the cell membrane.
C)   In all kinds of muscle it requires the entry of calcium from the extracellular fluid.
D)   Calcium-induced calcium-release plays a role in cardiac muscle cells, as well as in some smooth muscle cells.
E)   In skeletal muscle cells, excitation-contraction coupling begins when an action potential propagates along the sarcoplasmic reticulum membrane.

Exam 9: Muscle

Which is a TRUE statement about smooth muscle?

Correct AnswerverifiedShow Answer

In general, activating a slow-oxidative motor unit in a muscle will generate more tension than activating a fast-glycolytic motor unit.

Correct AnswerverifiedShow Answer

The step of the cross-bridge cycle that immediately follows the attachment of ATP to the myosin head is referred to as the "powerstroke."

Correct AnswerverifiedShow Answer

Which of these occurs during an isometric contraction of a skeletal muscle?

Correct AnswerverifiedC

What is the definition of a "motor unit"?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

During concentric contractions of skeletal muscle, the I band and H zone shorten but the A band stays the same.

Correct AnswerverifiedShow Answer

Characteristics of slow-oxidative fibers include numerous mitochondria, abundant myoglobin, and large stores of glycogen.

Correct AnswerverifiedShow Answer

Which of the following statements about different kinds of skeletal muscle fibers is TRUE?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

A large diameter is typical of which type of skeletal muscle fibers?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Binding of myosin to actin in skeletal muscle cells does not normally take place in the absence of Ca2+.

Correct AnswerverifiedTrue

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 Jim, John is likely to have:

Correct AnswerverifiedShow Answer

Why does breathing continue to be rapid and deep for a time after heavy exercise?

Correct AnswerverifiedShow Answer

Which type of skeletal muscle fibers fatigues most quickly?

Correct AnswerverifiedShow Answer

Fast fibers can be distinguished from slow fibers by the rate at which their myosin-ATPases split ATP.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedB

Which is a TRUE statement about excitation-contraction coupling?

Correct AnswerverifiedShow Answer

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C

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

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Binding of myosin to actin in skeletal muscle cells does not normally take place in the absence of Ca²⁺.

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True

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B

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