Question 1

Which of the following best describes the sequence of events that occur during the latent period of skeletal muscle contraction?

Accepted Answer

Action potential travels along the sarcolemma, Ca$$^{2+} is $$released from the sarcoplasmic reticulum, and cross-bridge cycling begins.

Question 2

During excitation-contraction coupling in skeletal muscle, what is the primary role of Ca$$^{2+}$$ ions?

Accepted Answer

Ca$$^{2+}$$ binds to troponin, causing a conformational change that moves tropomyosin away from actin's binding sites.

Question 3

Which of the following best explains why skeletal muscle contraction ceases when acetylcholine is removed from the synaptic cleft?

Accepted Answer

The sarcoplasmic reticulum stops releasing Ca$$^{2+}$$, and Ca$$^{2+} is $$actively pumped back, leading to muscle relaxation.

Question 4

A patient is given a drug that blocks voltage-gated Na$$^+$$ channels in skeletal muscle. What is the most likely effect on muscle contraction?

Accepted Answer

The muscle will be unable to generate action potentials, preventing contraction.

Question 5

Which of the following best describes the difference between isotonic and isometric muscle contractions?

Accepted Answer

Isotonic contractions involve muscle shortening or lengthening with constant tension, while isometric contractions generate tension without changing muscle length.

Question 6

Which of the following scenarios best illustrates the concept of motor unit recruitment in skeletal muscle?

Accepted Answer

A person lifting a light object uses only a few motor units, but as the object gets heavier, more motor units are activated.

Question 7

Which of the following best explains the physiological basis of muscle fatigue during prolonged exercise?

Accepted Answer

Depletion of ATP and accumulation of metabolic byproducts such as lactic acid impair cross-bridge cycling.

Question 8

A patient with a genetic defect in the ryanodine receptor (RyR1) in skeletal muscle is most likely to experience which of the following?

Accepted Answer

Impaired release of Ca$$^{2+}$$ from the sarcoplasmic reticulum, leading to weak or absent muscle contractions.

Question 9

Which of the following best describes the Frank-Starling law of the heart?

Accepted Answer

The greater the end-diastolic volume, the greater the force of contraction, up to a physiological limit.

Question 10

During the cardiac cycle, which event is associated with the opening of the aortic valve?

Accepted Answer

Ventricular pressure exceeds aortic pressure, initiating ventricular ejection.

Question 11

Which of the following best explains the plateau phase (phase 2) of the cardiac action potential in ventricular myocytes?

Accepted Answer

It is caused by a balance between Ca$$^{2+}$$ influx through L-type channels and K$$^+$$ efflux.

Question 12

A patient has a mutation that causes delayed closure of voltage-gated K$$^+$$ channels in cardiac muscle. What is the most likely effect on the cardiac action potential?

Accepted Answer

Prolonged repolarization phase, increasing the risk of arrhythmias.

Question 13

Which of the following best describes the function of the Purkinje fibers in the cardiac conduction system?

Accepted Answer

They rapidly conduct action potentials to ventricular muscle cells, ensuring coordinated contraction.

Question 14

Which of the following best explains the significance of the QRS complex on an ECG?

Accepted Answer

It represents ventricular depolarization, which precedes ventricular contraction.

Question 15

During isovolumetric contraction in the cardiac cycle, which of the following is true?

Accepted Answer

All heart valves are closed, and ventricular pressure rises rapidly.

Question 16

Which of the following best describes the role of the autonomic nervous system in regulating heart rate?

Accepted Answer

Sympathetic stimulation increases heart rate by increasing the slope of phase 4 depolarization in SA node cells.

Question 17

A patient is experiencing heart failure with reduced ejection fraction. Which of the following best explains the underlying problem?

Accepted Answer

The ventricles are unable to contract effectively, resulting in decreased stroke volume.

Question 18

Which of the following best describes the changes in ventricular volume during the phases of the cardiac cycle?

Accepted Answer

Ventricular volume increases during diastole (filling), remains constant during isovolumetric phases, and decreases during systole (ejection).

Muscle Physiology and Cardiac Function: Structured Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards