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 calcium ions necessary for muscle contraction.

Question 2

During the sliding filament mechanism of muscle contraction, which event directly causes the sarcomere to shorten?

Accepted Answer

Myosin heads pull actin filaments toward the M line.

Question 3

Which of the following is true regarding the structure of a skeletal muscle fiber?

Accepted Answer

It contains multiple nuclei and is surrounded by endomysium.

Question 4

A patient is experiencing muscle weakness due to a defect in acetylcholine (ACh) release at the neuromuscular junction. Which process is most directly impaired?

Accepted Answer

Transmission of the action potential from the neuron to the muscle fiber.

Question 5

Which equation correctly represents the hydrolysis of ATP during the cross-bridge cycle?

Accepted Answer

$$ATP \rightarrow ADP + P_i$$

Question 6

What is the primary role of troponin in skeletal muscle contraction?

Accepted Answer

It binds calcium ions, causing tropomyosin to move and expose actin's active sites.

Question 7

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.

Question 8

A muscle fiber is stimulated at a frequency of 90 times per second, resulting in a sustained contraction with no visible relaxation. What is this phenomenon called?

Accepted Answer

Fused (complete) tetanus

Question 9

Which of the following structures anchors thin filaments in place and serves as an attachment point for elastic filaments in the sarcomere?

Accepted Answer

Z-disc

Question 10

During muscle relaxation, which of the following events occurs first?

Accepted Answer

Motor neuron action potentials stop signaling for acetylcholine release.

Question 11

Which type of muscle tissue is involuntary, striated, and contains intercalated discs?

Accepted Answer

Cardiac muscle

Question 12

A laboratory experiment measures the tension produced by a single muscle fiber in response to repeated stimulation. Which pattern would you expect if the fiber is stimulated before it fully relaxes each time?

Accepted Answer

Unfused (incomplete) tetanus

Question 13

Which of the following best describes the role of titin in the sarcomere?

Accepted Answer

It stabilizes the myofibril structure and resists excessive stretching.

Question 14

If a drug blocks the reuptake of calcium ions into the sarcoplasmic reticulum, what would be the most immediate effect on muscle contraction?

Accepted Answer

The muscle would remain contracted due to sustained cross-bridge cycling.

Question 15

Which of the following correctly matches the band or zone with its filament composition in the sarcomere?

Accepted Answer

I band: only thin filaments

Question 16

A patient with a genetic mutation affecting tropomyosin is likely to experience which of the following symptoms?

Accepted Answer

Impaired regulation of muscle contraction due to inability to block actin's active sites.

Question 17

Which of the following best explains why the A band does not change in length during muscle contraction?

Accepted Answer

The length of thick filaments remains constant as thin filaments slide past them.

Question 18

Which of the following is the correct sequence of events in the cross-bridge cycle?

Accepted Answer

ATP hydrolysis, cross-bridge formation, power stroke, cross-bridge detachment

Question 19

Which of the following best describes the function of the perimysium in skeletal muscle?

Accepted Answer

It surrounds bundles of muscle fibers (fascicles) and provides support.

Question 20

A muscle fiber is unable to relax after contraction. Which of the following is the most likely explanation?

Accepted Answer

ATP is unavailable to detach myosin heads from actin.

Chapter 10: Muscle Tissue and Physiology – Structure and Function

Guida di studio - Domande di pratica

Study guide - Flashcard