Biology [2 Mark Question Answer]

The parts of the alimentary canal which produce hormones are the stomach and intestine. The stomach produces a hormone Gastrin. It stimulates the gastric glands to secrete gastric juices.

The endocrine glands are ductless glands which secrete hormones. They are poured directly into the blood stream and carried to different parts of the body. Hormones act as chemical messengers and coordinate the activities of various body organs. Chemically, hormones are proteins, amino acids or steroids.

A hormone is defined as a chemical substance produced by the endocrine glands situated in one part of the body and carried by the blood to some other parts of the body in order to exert its regulating and co-ordination effect on the cells of a specific organ or tissue.

Functions of pituitary gland:

1. Regulates growth.
2. Influences the thyroid gland, the adrenals and gonads.
3. Can produce changes in the skin colour of many amphibians.
4. Influence migration and nest buildings in birds.
5. Controls and stimulates the secretion of other endocrine glands.

The thymus gland is located in the mediastinum in front of the heart. This secretes a hormone thymosin which stimulates the lymphocytes to destroy invading microorganisms and antigens. It degenerates on aging, decreasing the immunity in old age.

Iodine is the active ingredient in the production of thyroxin hormone. If there is insufficient quantity of iodine in food, the thyroxin hormone is not produced. As a result, thyroid gland increases in size which is Visible as a swelling in the neck. This condition is known as goitre.

Functions of adrenal glands:

1. Prepare the body for emergencies.
2. Regulate the kidney in maintaining salt and water balance.
3. Control blood pressure and pulse rate.
4. Control concentration of sodium, potassium and sugar in the body.
5. Control some sexual characteristics.
6. Influence the breakdown of tissue proteins into amino acids.

Adrenal medulla secretes adrenaline. It controls heart beat and blood pressure and helps in providing glucose to the body in order to overcome emergency situations. It is also called the emergency hormone.

Insulin is a protein hormone and if it is given orally it would be acted upon by the protein digesting enzymes in the alimentary tract. So it is injected into the body of highly diabetic patient and is able to travel in the blood stream to bring about the required specific effect.

Pancreas is a heterocrine or myxocrine gland, as it contains two types of secretary structures, i.e., (i) Islet of Langerhans which secrete hormones insulin and glucagon, and these are transported by way of blood, and (ii) Acini that secretes pancreatic juice that is transported by way of ducts.

Glucagon: It raises the blood glucose levels by stimulating the breakdown of glycogen to glucose in the liver.
Insulin: It maintains the levels of glucose (sugar) in the blood.

(1) Alpha cells of islet of Langerhans
(2) Beta cells of islet of Langerhans.