Question 1

Which of the following best describes the function of the sarcoplasmic reticulum (SR) in skeletal muscle fibers?

Accepted Answer

It stores and releases $$\mathrm{Ca$$^{2+}$$}$$ ions to trigger muscle contraction.

Question 2

During the crossbridge cycle, what event directly causes the power stroke that moves actin filaments?

Accepted Answer

Release of ADP and inorganic phosphate ($$\mathrm{P_i}) $$from the myosin head.

Question 3

Which of the following best explains why a lack of extracellular $$\mathrm{Ca$$^{2+}$$}$$ would impair neurotransmitter release at the neuromuscular junction?

Accepted Answer

$$\mathrm{Ca$$^{2+}$$}$$ influx into the presynaptic terminal is required for vesicle fusion and acetylcholine release.

Question 4

A patient is given a drug that blocks voltage-gated sodium ($$\mathrm{Na^+}) $$channels in motor neurons. What is the most likely effect on muscle contraction?

Accepted Answer

Action potentials will not be generated, preventing muscle contraction.

Question 5

Which of the following best describes the difference between the two binding sites on the myosin head?

Accepted Answer

One site binds actin, and the other binds ATP.

Question 6

If a muscle fiber is stimulated at a frequency that allows complete relaxation between stimuli, what type of contraction occurs?

Accepted Answer

Treppe (staircase effect)

Question 7

Which of the following statements about the size principle of motor unit recruitment is correct?

Accepted Answer

Smaller motor units are recruited first, followed by larger units as more force is needed.

Question 8

A muscle is stretched beyond its optimal length before contraction. According to the length-tension relationship, what will happen to the force produced?

Accepted Answer

The force will decrease because there is less overlap between actin and myosin.

Question 9

Which of the following is a key difference between skeletal and cardiac muscle contraction?

Accepted Answer

Cardiac muscle contraction can be initiated by pacemaker cells, while skeletal muscle requires neural stimulation.

Question 10

During excitation-contraction coupling in skeletal muscle, which sequence of events is correct?

Accepted Answer

Action potential → $$\mathrm{Ca$$^{2+}$$}$$ release from SR → Troponin activation → Crossbridge formation

Question 11

Which of the following best explains why smooth muscle contraction is slower than skeletal muscle contraction?

Accepted Answer

Smooth muscle relies on $$\mathrm{Ca$$^{2+}$$}-$$calmodulin activation of MLCK rather than troponin.

Question 12

A muscle is producing maximum tension with no visible relaxation between stimuli. What is this phenomenon called?

Accepted Answer

Complete (fused) tetanus

Question 13

Which of the following is true regarding the role of ATP in muscle contraction?

Accepted Answer

ATP is required to detach the myosin head from actin after the power stroke.

Question 14

A patient with a genetic defect in the ryanodine receptor would most likely have problems with which process?

Accepted Answer

Release of $$\mathrm{Ca$$^{2+}$$}$$ from the sarcoplasmic reticulum

Question 15

Which of the following best describes the effect of increasing the number of active motor units in a muscle?

Accepted Answer

The total force produced by the muscle increases.

Question 16

Which of the following is a characteristic unique to skeletal muscle compared to cardiac and smooth muscle?

Accepted Answer

Presence of a motor end plate

Question 17

If a muscle is unable to relax after contraction, which of the following is the most likely cause?

Accepted Answer

Failure to reuptake $$\mathrm{Ca$$^{2+}$$}$$ into the sarcoplasmic reticulum

Question 18

Which of the following best explains the difference between Treppe and Tetanus in muscle contraction?

Accepted Answer

Treppe shows a staircase increase in tension with each stimulus, while tetanus is a sustained contraction with no relaxation.

Question 19

Which of the following is true regarding the effect of muscle fiber diameter on force production?

Accepted Answer

Larger diameter fibers produce more force due to more myofibrils.

Question 20

Which of the following is a function of the T-tubules in skeletal muscle fibers?

Accepted Answer

They conduct action potentials deep into the muscle fiber.

Chapter 12: Muscle Physiology – Structured Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards