Question 5 from UPSC CSE 2024 - Basic Science

Question

Which one of the following is synthesized in the human body that dilates blood vessels and increases blood flow?

IASCODEX · Accepted Answer

Correct Option: A. Nitric oxide

Strategy: Focus on the precise action mentioned — vasodilation and increased blood flow. Among the options, only nitric oxide is known for this function in human physiology. The rest are either not produced in the body or are not involved in such biological processes. Quick factual recall confirms nitric oxide as the correct answer.

Key Info: Nitric oxide (NO) is a gaseous signaling molecule synthesized in the human body, primarily by endothelial cells lining the blood vessels. It is produced from the amino acid L-arginine through the action of the enzyme nitric oxide synthase (NOS). Nitric oxide is a potent vasodilator, relaxing smooth muscle in vessel walls and leading to dilation (widening) of blood vessels, thereby increasing blood flow and reducing blood pressure. NO plays key roles in cardiovascular health, neurotransmission, and immune responses.

Nitrous oxide (N2O), also known as 'laughing gas', is not synthesized in the body and is used as an anesthetic. Nitrogen dioxide (NO2) and nitrogen pentoxide (N2O5) are environmental pollutants and not produced physiologically; they have no vasodilatory role in the human body.

Nitric oxide's discovery as a biological messenger revolutionized cardiovascular medicine, earning the 1998 Nobel Prize in Physiology or Medicine for its role in vasodilation.

IASCODEX · Answer

Option B: Nitrous oxide

IASCODEX · Answer

Option C: Nitrogen dioxide

IASCODEX · Answer

Option D: Nitrogen pentoxide