Q: A person is exercising and their heart rate (HR) increases from 70 bpm to 140 bpm, while their stroke volume (SV) remains constant at 70 mL. What is the new cardiac output (CO)? Use the formula $$CO = HR \times SV.$$

$$CO = 140 \times 70 = 9800\ mL/min$$

Question 1

Which of the following best describes the function of the T-tubules in skeletal muscle fibers?

Accepted Answer

They transmit action potentials deep into the muscle fiber, ensuring rapid and uniform contraction.

Question 2

During the sliding filament theory of muscle contraction, which two molecules are essential for cross-bridge cycling?

Accepted Answer

ATP and $$Ca^{2+}$$

Question 3

A patient is exposed to a drug that blocks voltage-gated $$Ca^{2+}$$ channels in the sarcoplasmic reticulum of skeletal muscle. What is the most immediate effect on muscle contraction?

Accepted Answer

The muscle will be unable to initiate contraction due to lack of $$Ca^{2+}$$ release.

Question 4

Which of the following best explains why cardiac contractile cells do not exhibit temporal summation like skeletal muscle cells?

Accepted Answer

Cardiac cells have a prolonged refractory period due to the plateau phase of their action potential.

Question 5

A person is exercising and their heart rate (HR) increases from 70 bpm to 140 bpm, while their stroke volume (SV) remains constant at 70 mL. What is the new cardiac output (CO)? Use the formula $$CO = HR 	imes SV.$$

Accepted Answer

$$CO = 140 	imes 70 = 9800\ mL/min$$

Question 6

Which of the following statements about the Frank-Starling law of the heart is correct?

Accepted Answer

Increasing end-diastolic volume (EDV) leads to a stronger contraction and increased stroke volume.

Question 7

Which type of capillary is most common in the body and found in muscle and skin?

Accepted Answer

Continuous capillaries

Question 8

If the baroreceptors in the carotid sinus detect an increase in blood pressure, what is the immediate effect on sympathetic nervous system activity and peripheral resistance?

Accepted Answer

Sympathetic activity decreases, causing vasodilation and decreased peripheral resistance.

Question 9

Which of the following best describes the role of the chordae tendineae in the heart?

Accepted Answer

They prevent the atrioventricular valves from inverting into the atria during ventricular contraction.

Question 10

A patient has a missing P wave on their ECG. What does this most likely indicate?

Accepted Answer

Atrial depolarization is absent, possibly due to SA node dysfunction.

Question 11

Which of the following equations correctly represents mean arterial pressure (MAP)?

Accepted Answer

$$MAP = CO 	imes R$$

Question 12

Which adrenergic receptor is primarily responsible for vasoconstriction of arterioles in response to sympathetic stimulation?

Accepted Answer

Alpha-1 receptor

Question 13

Which of the following best describes the difference between veins and arteries?

Accepted Answer

Arteries carry blood away from the heart; veins carry blood toward the heart.

Question 14

Which of the following events occurs immediately after the QRS complex on an ECG?

Accepted Answer

Ventricular contraction (systole)

Question 15

A skeletal muscle fiber is stimulated with increasing frequency. What is the expected effect on muscle contraction?

Accepted Answer

Contractions become smoother and may reach fused tetanus.

Question 16

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

Accepted Answer

Small, more excitable motor units are recruited first, followed by larger, less excitable units as load increases.

Question 17

Which of the following is a direct effect of norepinephrine (NE) binding to beta-1 adrenergic receptors on cardiac pacemaker cells?

Accepted Answer

Increased heart rate

Question 18

Which of the following best describes the function of precapillary sphincters?

Accepted Answer

They regulate blood flow into capillary beds by constricting or relaxing.

Question 19

If a person loses a significant amount of blood, which organ is primarily responsible for long-term regulation of blood volume and mean arterial pressure (MAP)?

Accepted Answer

Kidneys

Question 20

Which of the following best describes the effect of acetylcholine (ACh) on cardiac pacemaker cells?

Accepted Answer

It decreases the frequency of action potentials, lowering heart rate.

Muscle, Cardiovascular, and Blood Pressure Physiology: Study Guide

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