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Which class of arteries is most involved in regulating blood pressure through vasoconstriction and vasodilation?

A.

Capillaries

B.

Elastic arteries

C.

Arterioles

D.

Veins

Answer and Explanation

The Correct Answer is C

A. Capillaries:
 Capillaries are the sites of nutrient and gas exchange and have very thin walls; they do not actively regulate blood pressure.

B. Elastic arteries:
 Elastic arteries (e.g., aorta) maintain pressure by stretching and recoiling but are not the primary site of active vasoconstriction or vasodilation.

C. Arterioles:
 Arterioles are the resistance vessels of the circulatory system. Their smooth muscle can constrict or dilate in response to neural, hormonal, and local chemical signals, directly regulating blood pressure and blood flow to tissues.

D. Veins:
 Veins act as capacitance vessels and have some smooth muscle, but their role in blood pressure regulation is limited compared to arterioles.


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Related Questions

Correct Answer is D

Explanation

A. Fifth intercostal space, midclavicular line:
This is the location for auscultating the mitral valve, not the aortic valve.

B. Second intercostal space, left sternal border:
This is the typical location for the pulmonic valve, at the left upper sternal border.

C. Fourth intercostal space, left sternal border:
This area corresponds to the tricuspid valve, along the lower left sternal border.

D. Second intercostal space, right sternal border:
The aortic valve is best heard at the second intercostal space, right sternal border, which is the upper right portion of the heart base. This is important for detecting aortic stenosis or other semilunar valve abnormalities.

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.

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