The functional unit of the nervous system is: MCQ with Answer and Explanation

Explanation:
RNA is typically single-stranded (A true), but it contains ribose, not deoxyribose. Deoxyribose is in DNA. Thus R is false.

Explanation:
Capillaries are the smallest blood vessels, with walls only one cell thick (endothelium), facilitating diffusion of oxygen, carbon dioxide, nutrients, and waste products between blood and tissues. Arteries and veins have thicker walls with smooth muscle and connective tissue. Capillaries form extensive networks (capillary beds) throughout the body.

Explanation:
The SA node, located in the right atrium, spontaneously generates electrical impulses, setting the heart rate. It is the natural pacemaker. The AV node delays the impulse before it reaches the ventricles.