Question

_____ is a potent vasodilator.
A- Histamine
B- Serotonin
C- Codeine
D- Cimetidine

Answer 1

Hint: We know that vasodilator is used for the smooth functioning of all blood vessels. Vasodilator regulates the blood and oxygen flow in the body which are functioning abnormally. Vasodilators are also useful in relaxing muscles.

Complete step by step answer:
We know that vasodilator involves relaxation of smooth muscles near the blood vessels. Arteries have smooth inner walls that regulate the blood flow throughout the body, sometimes these arteries may develop some obstruction which reduces the blood flow by contraction of artery walls.
So, vasodilators are required for clearing the obstruction present. A potent vasodilator relaxes the walls of arteries and widens the blood vessels. Thus, vasodilators reduce high blood pressure and bring down to a normal level.
Among the given options Serotonin causes narrowing of blood vessels and increases blood pressure. So, Serotonin cannot be used as a potent vasodilator. Codeine does not function as a potent vasodilator and triggers some other diseases. Cimetidine is also harmful as it increases blood pressure and causes hypertension. Cimetidine causes the narrowing of blood vessels.
Histamine widens the blood vessels and ensures proper functioning of arteries and veins. Histamine binds to the walls and helps in increasing the flow of blood.

Hence option A is correct.

Note: Though histamine is a potent vasodilator it has many other functions such as Gastric acid release, sleep-wake regulation, etc. Serotonin regulates blood clotting of the blood vessels from the brain. It shows the reverse effect on blood vessels from arteries.