Question 1

Which of the following best describes the organization of a skeletal muscle from smallest to largest structural unit?

Accepted Answer

Myofibril, muscle fiber, fascicle, whole muscle

Question 2

During muscle contraction, which band in the sarcomere shortens, and which remains the same length?

Accepted Answer

The I band shortens, while the A band remains the same length.

Question 3

Which equation correctly represents the relationship between force, cross-sectional area, and muscle tension?

Accepted Answer

$$T = \frac{F}{A}$$

Question 4

A patient presents with muscle weakness due to a defect in the acetylcholine receptor at the neuromuscular junction. Which process is most directly impaired?

Accepted Answer

Depolarization of the muscle cell membrane

Question 5

Which of the following best explains the role of tropomyosin and troponin in skeletal muscle contraction?

Accepted Answer

They regulate the binding of myosin to actin by controlling access to the binding sites.

Question 6

Which of the following is TRUE regarding the events at the neuromuscular junction?

Accepted Answer

Acetylcholine is released from the motor neuron and binds to receptors on the muscle cell membrane, causing sodium influx.

Question 7

Which statement best describes the difference between isotonic and isometric muscle contractions?

Accepted Answer

Isotonic contractions change muscle length, while isometric contractions maintain muscle length.

Question 8

A sprinter experiences muscle fatigue after repeated sprints. Which physiological change is most likely responsible?

Accepted Answer

Accumulation of lactic acid in muscle cells

Question 9

Which of the following best describes the function of the sarcoplasmic reticulum in skeletal muscle cells?

Accepted Answer

It stores and releases calcium ions necessary for muscle contraction.

Question 10

During the recovery period after muscle contraction, which process helps restore resting conditions in the muscle cell?

Accepted Answer

Active transport of calcium ions back into the sarcoplasmic reticulum

Question 11

Which equation correctly represents the calculation of membrane potential using the Nernst equation for potassium ions?

Accepted Answer

$$E_K = \frac{RT}{zF} \ln \left( \frac{[K^+]_{out}}{[K^+]_{in}} \right)$$

Question 12

A patient is diagnosed with myasthenia gravis, an autoimmune disorder affecting the neuromuscular junction. Which symptom is most likely observed?

Accepted Answer

Progressive muscle weakness with repeated use

Question 13

Which of the following best describes the difference between fast-twitch and slow-twitch muscle fibers?

Accepted Answer

Fast-twitch fibers contract quickly and fatigue rapidly; slow-twitch fibers contract slowly and resist fatigue.

Question 14

Which process occurs first during excitation-contraction coupling in skeletal muscle?

Accepted Answer

Release of acetylcholine from the motor neuron

Question 15

Which of the following is a function of the sodium-potassium pump in maintaining the resting membrane potential?

Accepted Answer

It actively transports 3 sodium ions out and 2 potassium ions into the cell.

Question 16

A muscle is stimulated repeatedly at a high frequency, resulting in a sustained contraction without relaxation. What is this phenomenon called?

Accepted Answer

Tetanus

Question 17

Which of the following best explains why cardiac muscle cells do not experience tetanus under normal physiological conditions?

Accepted Answer

Cardiac muscle cells have a long refractory period that prevents sustained contractions.

Question 18

Which equation correctly represents the calculation of the equilibrium potential for sodium ions using the Nernst equation?

Accepted Answer

$$E_{Na} = \frac{RT}{zF} \ln \left( \frac{[Na^+]_{out}}{[Na^+]_{in}} \right)$$

Question 19

A patient is unable to relax their muscles after contraction, resulting in continuous muscle stiffness. Which ion imbalance is most likely responsible?

Accepted Answer

Failure to remove calcium ions from the cytoplasm

Muscle Tissue and Nervous System: Organization, Physiology, and Function

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