Question 1

Which of the following best describes the role of acetylcholine at the neuromuscular junction during skeletal muscle contraction?

Accepted Answer

It binds to receptors on the motor end plate, opening ion channels that allow sodium influx and depolarization of the muscle fiber.

Question 2

During the cross-bridge cycle in skeletal muscle, which event directly requires ATP hydrolysis?

Accepted Answer

Detachment of myosin from actin after the power stroke

Question 3

A patient is experiencing muscle fatigue after prolonged exercise. Which of the following is the most likely cause according to the study materials?

Accepted Answer

Accumulation of lactic acid and changes in pH

Question 4

Which equation correctly represents the transfer of a phosphate group from creatine phosphate to ADP to form ATP in skeletal muscle?

Accepted Answer

$$\mathrm{Creatine~phosphate} + \mathrm{ADP} \rightarrow \mathrm{Creatine} + \mathrm{ATP}$$

Question 5

Which of the following best explains why fast-glycolytic muscle fibers fatigue more quickly than slow-oxidative fibers?

Accepted Answer

Fast-glycolytic fibers have fewer mitochondria and rely primarily on anaerobic metabolism.

Question 6

A muscle is contracting isometrically. Which of the following is true about the muscle’s length and tension?

Accepted Answer

The muscle length remains constant while tension increases.

Question 7

Which of the following mechanisms is responsible for the relaxation of a contracted skeletal muscle fiber?

Accepted Answer

Active transport of calcium ions back into the sarcoplasmic reticulum

Question 8

Which statement best describes the difference between smooth muscle and skeletal muscle contraction?

Accepted Answer

Smooth muscle contraction is regulated by calcium binding to calmodulin, which activates myosin light-chain kinase.

Question 9

If the frequency of action potentials in a muscle fiber increases, what is the expected effect on muscle tension?

Accepted Answer

Muscle tension increases due to summation.

Question 10

Which of the following best explains the process of recruitment in whole-muscle contraction?

Accepted Answer

Activating additional motor units to increase the force produced by the muscle

Question 11

During prolonged, low-intensity exercise, which metabolic pathway is primarily responsible for ATP production in skeletal muscle?

Accepted Answer

Oxidative phosphorylation in mitochondria

Question 12

Which of the following is a characteristic of fast-glycolytic muscle fibers?

Accepted Answer

Large diameter and rapid contraction speed

Question 13

A muscle fiber is exposed to a toxin that blocks the reuptake of calcium into the sarcoplasmic reticulum. What is the most likely effect?

Accepted Answer

The muscle fiber will remain in a contracted state (tetany).

Question 14

Which of the following equations represents the net reaction for aerobic metabolism of glucose in muscle cells?

Accepted Answer

$$\mathrm{Glucose} + 6\mathrm{O}_2 \rightarrow 6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + 36\mathrm{ATP}$$

Question 15

Which of the following best describes the function of troponin in skeletal muscle contraction?

Accepted Answer

Troponin binds calcium, causing tropomyosin to move and expose myosin-binding sites on actin.

Question 16

Which of the following is true regarding the control of smooth muscle contraction?

Accepted Answer

Smooth muscle contraction can be triggered by hormones, neurotransmitters, or spontaneous depolarization.

Question 17

A muscle is performing an eccentric contraction. Which of the following best describes what is happening?

Accepted Answer

The muscle lengthens while generating tension.

Question 18

Which of the following statements about the three types of muscle tissue is correct?

Accepted Answer

Skeletal muscle is attached to bones and enables voluntary movement.

Question 19

Which of the following best explains why increasing the number of active motor units in a muscle increases the force of contraction?

Accepted Answer

More motor units means more muscle fibers are contracting simultaneously.

Skeletal and Smooth Muscle: Structure, Contraction, and Energy Metabolism

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