Question 1

Which of the following best describes the role of the sodium-potassium pump ($$\mathrm{Na^+/K^+}$$ ATPase) in skeletal muscle fibers?

Accepted Answer

It actively transports three sodium ions out of the cell and two potassium ions in, maintaining the resting membrane potential.

Question 2

A patient presents with muscle weakness and a waddling gait. Genetic testing reveals a mutation in the gene encoding dystrophin. Which of the following best explains the pathophysiology of this condition?

Accepted Answer

Dystrophin mutation disrupts the anchoring of the sarcolemma to the endomysium, resulting in muscle fiber death and replacement by connective tissue.

Question 3

During the contraction of a sarcomere, which of the following changes occur?

Accepted Answer

The I band and H zone narrow, while the A band remains unchanged.

Question 4

Which of the following is the correct sequence of events in the crossbridge cycle during muscle contraction?

Accepted Answer

ATP binds to myosin, myosin detaches from actin, ATP hydrolysis cocks the myosin head, myosin binds to actin, power stroke occurs.

Question 5

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

ATP is no longer produced, so myosin heads cannot detach from actin, resulting in sustained contraction.

Question 6

A muscle fiber is stimulated 80 times per second, resulting in a sustained contraction with maximal tension. What is this phenomenon called?

Accepted Answer

Fused (complete) tetanus

Question 7

Which of the following muscle fiber types would be most prevalent in the postural muscles of a marathon runner?

Accepted Answer

Type I (slow oxidative) fibers

Question 8

Which of the following best describes the role of acetylcholinesterase at the neuromuscular junction?

Accepted Answer

It degrades acetylcholine in the synaptic cleft, terminating the signal for muscle contraction.

Question 9

Which of the following is a unique property of cardiac muscle tissue compared to skeletal muscle tissue?

Accepted Answer

It contains intercalated discs that allow the heart to contract as a unit.

Question 10

A patient is unable to relax a muscle after contraction, resulting in a painful spasm. Which of the following is most likely impaired?

Accepted Answer

Function of acetylcholinesterase and calcium ion pumps in the sarcoplasmic reticulum

Question 11

Which of the following best describes the energy source that provides ATP for the first 10 seconds of maximal muscle activity?

Accepted Answer

Creatine phosphate reaction catalyzed by creatine kinase

Question 12

Which of the following is a characteristic of smooth muscle tissue?

Accepted Answer

It can contract up to 80% of its resting length and lacks troponin.

Question 13

Which of the following best explains the length-tension relationship in skeletal muscle?

Accepted Answer

Muscle tension is highest when the sarcomere is at its optimal length, allowing maximal crossbridge formation.

Question 14

Which of the following is a direct result of the depolarization phase of an action potential in a muscle fiber?

Accepted Answer

Voltage-gated sodium channels open and sodium ions enter the cell.

Question 15

Which of the following best describes the process of wave summation in muscle fibers?

Accepted Answer

Repeated stimulation before the muscle can fully relax results in greater tension with each contraction.

Question 16

Which of the following is a function of muscle tone in the body?

Accepted Answer

It maintains posture and stabilizes joints even when the muscle is relaxed.

Question 17

Which of the following best describes the difference between isotonic concentric and isotonic eccentric contractions?

Accepted Answer

In concentric contractions, the muscle shortens as it generates force greater than the load; in eccentric contractions, the muscle lengthens as the load exceeds the force generated.

Question 18

Which of the following is a likely cause of delayed-onset muscle soreness (DOMS) after unaccustomed exercise?

Accepted Answer

Minor structural damage to myofilaments, especially from isotonic eccentric contractions

Question 19

Which of the following adaptations would you expect in the skeletal muscles of an individual who undergoes endurance training?

Accepted Answer

Increase in oxidative enzymes, mitochondria, and blood vessels

Question 20

Which of the following best describes the role of myoglobin in muscle fibers?

Accepted Answer

It binds oxygen and releases it as needed for oxidative catabolism.

Muscle Tissue and Physiology: Structured Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards