Question 1

Which of the following best explains how graded contractions are possible in skeletal muscle, even though all action potentials are identical?

Accepted Answer

Graded contractions result from varying the number of motor units recruited, not from differences in action potential amplitude.

Question 2

During muscle contraction, which protein directly binds calcium to initiate the exposure of myosin-binding sites on actin?

Accepted Answer

Troponin

Question 3

A sprinter relies primarily on which type of muscle fiber for explosive, short-duration activity?

Accepted Answer

Type IIx (fast glycolytic fibers)

Question 4

Which of the following is a major difference between cardiac and skeletal muscle cells?

Accepted Answer

Cardiac muscle cells are connected by intercalated discs, allowing electrical impulses to spread cell-to-cell.

Question 5

Which equation correctly represents the formation of phosphocreatine in skeletal muscle during rest?

Accepted Answer

$$ \mathrm{Creatine} + \mathrm{ATP} \rightarrow \mathrm{Phosphocreatine} + \mathrm{ADP} $$

Question 6

A patient with muscle fatigue after intense exercise is most likely experiencing which of the following physiological changes?

Accepted Answer

Accumulation of extracellular $$ \mathrm{K}^+ $$ and depletion of stored glycogen

Question 7

Which of the following adaptations is most likely to occur in skeletal muscle after endurance training?

Accepted Answer

Increased number and size of mitochondria

Question 8

Which structure stores calcium ions in skeletal muscle fibers and releases them during excitation-contraction coupling?

Accepted Answer

Sarcoplasmic reticulum

Question 9

Which of the following best describes the sliding filament theory of muscle contraction?

Accepted Answer

Myosin heads bind to actin, perform a power stroke, and pull thin filaments toward the center of the sarcomere.

Question 10

Which of the following is true regarding smooth muscle contraction?

Accepted Answer

Smooth muscle can contract even when greatly stretched due to its arrangement of actin and myosin.

Question 11

A marathon runner is likely to have a higher proportion of which muscle fiber type in their leg muscles?

Accepted Answer

Type I (slow oxidative fibers)

Question 12

Which of the following is NOT a function of muscles?

Accepted Answer

Secretion of hormones

Question 13

Which process is responsible for actively pumping calcium back into the sarcoplasmic reticulum after muscle contraction?

Accepted Answer

Ca$$^{2+}-$$ATPase pump

Question 14

Which of the following best describes a motor unit?

Accepted Answer

A single motor neuron and all the muscle fibers it innervates

Question 15

Which of the following is a consequence of strength training on skeletal muscle fibers?

Accepted Answer

Hypertrophy due to increased actin and myosin content

Question 16

Which of the following is true regarding the length-tension relationship in skeletal muscle?

Accepted Answer

Muscle strength is affected by the initial length of the fiber at rest.

Question 17

Which of the following is a characteristic of cardiac muscle cells?

Accepted Answer

They can generate action potentials automatically due to pacemaker regions.

Question 18

Which of the following is a direct effect of oxygen debt after exercise?

Accepted Answer

Breathing rate remains elevated to metabolize lactic acid and restore ATP and phosphocreatine levels.

Muscle Physiology: Structure, Function, and Types of Muscle Tissue

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