Question 1

Which of the following best describes the role of the sarcoplasmic reticulum in skeletal muscle contraction?

Accepted Answer

It stores and releases Ca$$^{2+}$$ ions necessary for muscle contraction.

Question 2

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

Accepted Answer

The H zone and I band both shorten, while the A band remains constant.

Question 3

What is the primary function of T-tubules in skeletal muscle fibers?

Accepted Answer

To allow action potentials to penetrate deep into the muscle fiber.

Question 4

Which protein directly blocks the myosin-binding sites on actin in a relaxed muscle fiber?

Accepted Answer

Tropomyosin

Question 5

A patient is exposed to a toxin that inhibits acetylcholinesterase (AChE) at the neuromuscular junction. What is the most likely effect on muscle contraction?

Accepted Answer

Prolonged muscle contraction due to continued presence of acetylcholine in the synaptic cleft.

Question 6

Which of the following best explains why skeletal muscle fibers are multinucleated?

Accepted Answer

They are formed by the fusion of multiple myoblasts during development.

Question 7

Which event directly triggers the release of Ca$$^{2+}$$ from the sarcoplasmic reticulum during excitation-contraction coupling?

Accepted Answer

An action potential traveling down the T-tubule alters the conformation of the DHP receptor.

Question 8

Which of the following is true regarding the 'size principle' of motor unit recruitment?

Accepted Answer

Smaller, more excitable motor units are recruited before larger, less excitable ones.

Question 9

Which of the following best describes the function of acetylcholine at the neuromuscular junction?

Accepted Answer

It binds to nicotinic receptors on the motor end plate, causing Na$$^+$$ influx and depolarization.

Question 10

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

Accepted Answer

Failure of Ca$$^{2+}$$ reuptake into the sarcoplasmic reticulum by the SERCA pump.

Question 11

Which of the following muscle fiber types is most resistant to fatigue and is primarily used for posture?

Accepted Answer

Slow-twitch oxidative (Type I) fibers

Question 12

Which of the following best explains the phenomenon of wave (temporal) summation in skeletal muscle?

Accepted Answer

Increased frequency of stimulation leads to greater force because the muscle does not fully relax between stimuli.

Question 13

Which of the following correctly matches the muscle structure with its description?

Accepted Answer

Sarcolemma: the cell membrane of a muscle fiber

Question 14

Which of the following is required for the myosin head to detach from actin during the contraction cycle?

Accepted Answer

Binding of ATP to the myosin head

Question 15

A muscle is stimulated at a frequency that does not allow complete relaxation between stimuli, resulting in a sustained but quivering contraction. What is this phenomenon called?

Accepted Answer

Unfused (incomplete) tetanus

Question 16

Which of the following best describes the latent period of a muscle twitch?

Accepted Answer

It is the time between the application of a stimulus and the beginning of contraction, during which excitation-contraction coupling occurs.

Question 17

Which of the following statements about the A band in a sarcomere is correct?

Accepted Answer

It contains the entire length of the thick filaments and regions of overlap with thin filaments.

Question 18

Which of the following best explains why motor units are asynchronously activated during muscle contraction?

Accepted Answer

To prevent muscle fatigue by allowing some fibers to rest while others contract.

Question 19

Which of the following is a correct sequence of events in skeletal muscle contraction?

Accepted Answer

Action potential → Ca$$^{2+}$$ release → Troponin binds Ca$$^{2+}$$ → Tropomyosin moves → Myosin binds actin

Somatic Nervous System and Skeletal Muscle: Structure, Function, and Contraction

Guida di studio - Domande di pratica

Study guide - Flashcard