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Which of the following factors directly affects peripheral resistance and contributes to blood pressure regulation?

A.

Oxygen saturation

B.

Blood vessel diameter

C.

Venous return

D.

Heart rate

Answer and Explanation

The Correct Answer is B

A. Oxygen saturation:
 Oxygen saturation affects tissue oxygen delivery but does not directly influence vascular resistance.

B. Blood vessel diameter:
 Peripheral resistance is strongly influenced by vessel diameter. Vasoconstriction increases resistance and blood pressure, while vasodilation decreases resistance. This is a key determinant of systemic vascular resistance and blood pressure regulation.

C. Venous return:
 Venous return affects preload and cardiac output, indirectly influencing blood pressure, but it does not directly determine peripheral resistance.

D. Heart rate:
 Heart rate affects cardiac output but does not directly change peripheral resistance, which is primarily a function of arteriolar tone and vessel diameter.


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Related Questions

Correct Answer is C

Explanation

A. AV node:
The AV node serves as a secondary pacemaker and delays the conduction of impulses from the atria to the ventricles, allowing ventricular filling. It does not initiate the heartbeat under normal conditions.

B. Purkinje fibers:
Purkinje fibers distribute impulses rapidly throughout the ventricles but act as a backup pacemaker at 20-40 bpm if higher centers fail. They do not initiate the cardiac rhythm.

C. SA node:
The SA node, located in the right atrium near the superior vena cava, is the primary pacemaker of the heart. It generates impulses at 60-100 bpm, initiating atrial contraction and setting the overall heart rate. Dysfunction of the SA node leads to arrhythmias such as sick sinus syndrome.

D. Bundle of His:
The Bundle of His conducts impulses from the AV node to the ventricles but is not a primary pacemaker. Its rate is slower than the SA node and primarily ensures coordinated ventricular contraction.

Correct Answer is D

Explanation

A. To pump blood to the lungs for oxygenation:
The right ventricle pumps deoxygenated blood to the lungs. The left ventricle is responsible for systemic circulation.

B. To receive deoxygenated blood from the body:
The right atrium receives deoxygenated blood from the systemic veins.

C. To regulate heart rhythm:
Heart rhythm is controlled by the SA and AV nodes and the conduction system, not the ventricles themselves.

D. To pump oxygenated blood into systemic circulation:
The left ventricle has thick muscular walls that generate the high pressure needed to pump oxygen-rich blood through the aorta and systemic arteries to the entire body. Dysfunction leads to decreased perfusion and signs of left-sided heart failure.

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