Question

Assertion: Histamine is a potent vasodilator.
Reason: Histamine is responsible for the nasal congestion associated with common cold and allergic response to pollen.
A) Both assertion and reason are correct and reason is the correct explanation for the assertion.
B) Both assertion and reason are correct but reason is the not correct explanation for the assertion.
C)Assertion is correct but reason is incorrect.
D) Both assertion and reason are incorrect.

Answer 1

Histamine is an amine that is produced as part of a local immune response to cause inflammation. It also has a role as neurotransmitter and also in regulating the physiological function in the gut.

Complete answer:
Histamine is a biologically active substance found in a great variety of living organisms. It is chemically classified as an amine, an organic molecule based on the structure of ammonia. Let us analyze each option to find out the correct option.

Option A: Histamine is said to be a potent vasodilator. Vasodilators are a group of medicines that dilate blood vessels, which allows blood to flow more easily. The common functions of histamine are contraction of the smooth muscles in the bronchi and gut and relaxation of other muscles. It is also responsible for the nasal congestion associated with common cold and allergic response to pollen. So, Both assertion and reason are correct and reason. But, the reason is not the correct explanation of the assertion. Therefore, this is an incorrect option.
Option B: Histamine is a potent vasodilator. However, it has various functions. It contracts the smooth muscles in the bronchi and gut and relaxes other muscles, such as those in the walls of fine blood vessels. Histamine is also responsible for the nasal congestion associated with common cold and allergic response to pollen. So, both Assertion and Reason are correct but Reason is not the correct explanation for Assertion. Therefore, this is the correct option.
Option C: Histamine is said to be a potent vasodilator. The function of the histamine is nasal congestion associated with common cold and allergic response to pollen. Therefore, both assertion and reason is correct. Therefore, this is an incorrect option.
Option D: Histamine is a biologically active substance which acts as a vasodilator, i.e., it dilates blood vessels, which allows blood to flow more easily. The function of histamine is contraction of the smooth muscles in the bronchi and gut and relaxes other muscles,such as those in the walls of fine blood vessels. Histamine is also responsible for the nasal congestion associated with common cold and allergic response to pollen. So, both assertion and reason are incorrect. Therefore, this is an incorrect option.

Thus, the correct option is (B) Both assertion and reason are correct but reason is the not correct explanation for the assertion.

Note: The function of histamine in the body are as follows:

During allergic reactions they are one among the many mediators of allergic diseases and they have a primary role in anaphylaxis, rhinitis, etc.
In the body they can produce contraction of smooth muscle tissues of the stomach, uterus, lungs, etc.
In the GI tract histamine is involved in enhancement of gastric acid production, modulation of GI motility and alteration of mucosal ion secretion.