Release of phosphate ($$\text{P}_i) $$from myosin

Question 1

Which of the following best describes the physiological effect of curare on skeletal muscle contraction?

Accepted Answer

Curare prevents acetylcholine from binding to nicotinic receptors, resulting in muscle paralysis.

Question 2

During the cross-bridge cycle in skeletal muscle, which event directly triggers the power stroke?

Accepted Answer

Release of phosphate ($$	ext{P}_i) $$from myosin

Question 3

A patient exposed to tetrodotoxin would most likely experience which of the following effects on skeletal muscle?

Accepted Answer

Paralysis due to blocked voltage-gated Na+ channels preventing action potentials

Question 4

Which of the following best explains why slow-twitch muscle fibers are more resistant to fatigue than fast-twitch fibers?

Accepted Answer

They use oxidative phosphorylation and have abundant blood supply.

Question 5

In the sliding filament model, what happens to the length of the A band during muscle contraction?

Accepted Answer

The A band remains the same length as filaments slide.

Question 6

A muscle is stimulated repeatedly at a frequency that allows partial relaxation between contractions. Which term best describes this phenomenon?

Accepted Answer

Incomplete tetanus

Question 7

Which of the following is a primary cause of muscle fatigue during intense exercise?

Accepted Answer

Reduced sarcoplasmic reticulum Ca$$^{2+}$$ release and increased phosphate from phosphocreatine breakdown

Question 8

During high-intensity exercise (\u003e70% max intensity), which metabolic pathway is primarily used by skeletal muscle?

Accepted Answer

Glycolysis utilizing stored glycogen

Question 9

Which of the following best describes the physiological role of the SERCA pump in muscle relaxation?

Accepted Answer

It actively transports Ca$$^{2+}$$ back into the sarcoplasmic reticulum using ATP.

Question 10

Which sequence correctly represents the steps of a reflex arc?

Accepted Answer

Receptor → Sensory neuron → CNS integration center → Motor neuron → Effector

Question 11

Which of the following best explains the size principle of motor unit recruitment?

Accepted Answer

Small motor units are recruited first, followed by larger units as stimulus intensity increases.

Question 12

In smooth muscle contraction, which enzyme is activated by the Ca$$^{2+}-$$calmodulin complex?

Accepted Answer

Myosin light-chain kinase (MLCK)

Question 13

Which of the following statements about excitation-contraction coupling in cardiac muscle is correct?

Accepted Answer

Depolarization opens voltage-gated Ca$$^{2+}$$ channels, and Ca$$^{2+}$$ influx triggers calcium-induced calcium release from the SR.

Question 14

Which neurotransmitter and receptor combination is responsible for sympathetic vasoconstriction in blood vessels?

Accepted Answer

Norepinephrine and alpha-adrenergic receptors

Question 15

A muscle fiber is exposed to nerve gas, which inhibits acetylcholinesterase. What is the most likely effect?

Accepted Answer

Prolonged depolarization and possible muscle spasms due to excess ACh

Question 16

Which of the following best describes the oxygen deficit during exercise?

Accepted Answer

The difference between oxygen needed and oxygen immediately available, resulting in elevated post-exercise oxygen consumption (EPOC).

Question 17

Which event occurs during the relaxation phase of skeletal muscle contraction?

Accepted Answer

ATP-dependent pumps return Ca$$^{2+} to $$the sarcoplasmic reticulum.

Question 18

Which of the following is TRUE regarding the effect of sympathetic stimulation on the urinary tract?

Accepted Answer

Detrusor muscle relaxes and internal urethral sphincter contracts.

Question 19

Which of the following best describes the effect of asynchronous recruitment of motor units during sustained muscle activity?

Accepted Answer

It delays fatigue by alternating active motor units, allowing some to rest.

Muscle Physiology: Structure, Function, and Regulation

Study Guide - Practice Questions