Question 1

Which of the following best describes the role of the protein dystrophin in skeletal muscle fibers?

Accepted Answer

It anchors the sarcolemma to surrounding connective tissue and myofibrils.

Question 2

A patient presents with muscle weakness and is diagnosed with Duchenne Muscular Dystrophy. Which of the following is the most likely underlying cause?

Accepted Answer

Defective gene for the protein dystrophin on the X chromosome.

Question 3

Which of the following events occurs first during the excitation phase of skeletal muscle contraction?

Accepted Answer

Acetylcholine is released from the axon terminal into the synaptic cleft.

Question 4

During the crossbridge cycle, what is the direct result of ATP binding to the myosin head?

Accepted Answer

The myosin head detaches from the actin active site.

Question 5

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

Accepted Answer

ATP is no longer available to detach myosin heads from actin.

Question 6

A muscle fiber is stimulated repeatedly at a frequency of 90 stimuli per second. Which pattern of contraction is most likely to occur?

Accepted Answer

Fused (complete) tetanus

Question 7

Which of the following is a property shared by all three types of muscle tissue?

Accepted Answer

Ability to generate muscle tension

Question 8

Which of the following best describes the function of the sodium-potassium pump in skeletal muscle fibers?

Accepted Answer

It maintains the resting membrane potential by moving 3 Na$$^+$$ out and 2 K$$^+ in $$per ATP hydrolyzed.

Question 9

A patient receives an injection of botulinum toxin (Botox) in the facial muscles. What is the most direct effect at the neuromuscular junction?

Accepted Answer

Acetylcholine release from the motor neuron is blocked.

Question 10

Which of the following best explains why creatine supplementation may improve performance in short, high-intensity activities?

Accepted Answer

Creatine phosphate rapidly regenerates ATP for immediate energy needs.

Question 11

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

Accepted Answer

Maximum tension is generated when sarcomeres are at 100–120% of their natural length.

Question 12

Which of the following best describes the difference between single-unit and multi-unit smooth muscle?

Accepted Answer

Single-unit smooth muscle cells are connected by gap junctions and contract as a unit.

Question 13

Which of the following is the primary energy source for muscle contraction after the first minute of sustained activity?

Accepted Answer

Oxidative catabolism (aerobic metabolism)

Question 14

A person is unable to maintain an upright posture due to muscle fatigue. Which muscle fiber type is most likely depleted?

Accepted Answer

Type I (slow oxidative) fibers

Question 15

Which of the following best explains why cardiac muscle cells can contract without nervous system stimulation?

Accepted Answer

They contain pacemaker cells that spontaneously generate action potentials.

Question 16

Which of the following is required for muscle relaxation after contraction?

Accepted Answer

Active transport of calcium ions back into the sarcoplasmic reticulum using ATP.

Question 17

A muscle is contracting against a load that is heavier than the force it can generate, but its length does not change. What type of contraction is this?

Accepted Answer

Isometric contraction

Question 18

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

Accepted Answer

It binds and stores oxygen for use during aerobic metabolism.

Question 19

Which of the following is a likely consequence of disuse (atrophy) of skeletal muscle?

Accepted Answer

Decrease in the number of myofibrils and oxidative enzymes.

Question 20

Which of the following best explains why wave summation leads to increased muscle tension?

Accepted Answer

Calcium ions accumulate in the cytosol, allowing more crossbridges to form.

Muscle Tissue and Physiology: Structured Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards