Question 1

Which of the following best explains why the A band remains the same length during skeletal muscle contraction, while the I band and H zone shorten?

Accepted Answer

The A band corresponds to the length of the thick filaments, which do not change length as filaments slide past each other.

Question 2

A patient is given a drug that inhibits acetylcholinesterase (AChE). What is the most likely effect on skeletal muscle contraction?

Accepted Answer

Muscle contraction will be stronger and prolonged due to increased acetylcholine availability.

Question 3

Which sequence correctly describes the order of events in the sliding filament theory of muscle contraction?

Accepted Answer

ATP binds myosin → Myosin detaches from actin → ATP hydrolysis → Myosin binds actin → Power stroke

Question 4

A person with myasthenia gravis experiences muscle weakness because:

Accepted Answer

Acetylcholine receptors are destroyed, reducing muscle fiber depolarization.

Question 5

Which of the following best describes the role of calcium in smooth muscle contraction?

Accepted Answer

Calcium binds to calmodulin, activating myosin light-chain kinase (MLCK) to phosphorylate myosin.

Question 6

A patient presents with muscle stiffness several hours after death. Which of the following best explains this phenomenon (rigor mortis)?

Accepted Answer

ATP depletion prevents myosin heads from detaching from actin, causing sustained contraction.

Question 7

Which of the following is TRUE regarding the plateau phase of the cardiac action potential in myocardial contractile cells?

Accepted Answer

It prevents tetanic contractions, ensuring coordinated heartbeats.

Question 8

A 65-year-old patient is diagnosed with an AV block. Which of the following ECG findings would you expect?

Accepted Answer

Abnormal relationship between P waves and QRS complexes.

Question 9

Calculate the pulse pressure for a patient with a systolic blood pressure of $$130\ \mathrm{mmHg}$$ and a diastolic blood pressure of $$80\ \mathrm{mmHg}.$$

Accepted Answer

$$50\ \mathrm{mmHg}$$

Question 10

Which of the following best describes the effect of vasoconstriction on blood pressure, according to the equation $$BP = CO 	imes PR$$?

Accepted Answer

Vasoconstriction increases peripheral resistance, raising blood pressure.

Question 11

A patient is given a calcium channel blocker. Which of the following effects would you expect?

Accepted Answer

Decreased heart rate and contractility due to reduced calcium entry into cardiac cells.

Question 12

Which of the following best explains why the SA node, and not the AV node, normally sets the heart rate?

Accepted Answer

The SA node has the fastest spontaneous depolarization rate due to its pacemaker potential.

Question 13

Which of the following is the correct formula for cardiac output (CO), and what does each variable represent?

Accepted Answer

$$CO = HR 	imes SV$$, where $$HR is $$heart rate and $$SV is $$stroke volume.

Question 14

During the cardiac cycle, which event occurs immediately after the closure of the AV valves?

Accepted Answer

Isovolumetric contraction

Question 15

A sudden drop in blood pressure is detected by baroreceptors in the carotid sinus. What is the immediate physiological response?

Accepted Answer

Increased heart rate and vasoconstriction

Question 16

Which of the following best describes the function of muscle spindles and Golgi tendon organs?

Accepted Answer

Muscle spindles detect stretch and cause contraction; Golgi tendon organs detect tension and inhibit contraction.

Question 17

A patient’s ECG shows a normal P wave, a widened QRS complex, and an absent T wave. Which phase of the cardiac cycle is most likely affected?

Accepted Answer

Ventricular depolarization and repolarization

Question 18

According to the Frank–Starling law, what happens to stroke volume if end-diastolic volume (EDV) increases, assuming all other factors remain constant?

Accepted Answer

Stroke volume increases due to greater ventricular stretch.

Question 19

Which of the following best describes the role of interneurons in the spinal cord during voluntary movement?

Accepted Answer

They prevent antagonistic muscle contraction, ensuring smooth movement.

Muscle Physiology, Motor Control, Cardiac Electrophysiology, and Hemodynamics: ANP Study Guide

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