Biology [3 marks Question Answer]

General properties of hormones:

1. Hormones are secreted by the endocrine glands.
2. Hormones are specific in function.
3. Hormonal actions are long lasting.
4. Hormones are required in very minute quantities.
5. They are secreted independent of one another.
6. They act as chemical co-ordinators or chemical messengers.
7. They are proteinaceous or steroid in nature..
8. They are secreted in response to specific stimuli.

Two kinds of diabetes are:
(i) Diabetes insipidus (ii) Diabetes mellitus.
Symptoms and causes of diabetes insipidus:
(i) It is due to deficiency of antidiuretic hormone (ADH).
(ii) In this urination is frequent and copious, resulting in loss of water from the body and the person feels thirsty.
Symptoms and causes of diabetes mellitus:
(i) It is due to insufficient secretion of insulin hormone.
(ii) Presence of glucose in urine and high level of glucose in blood.

Exophthalmic goitre or Grave’s disease is caused by overactivity of the thyroid gland. The thyroid increases in size and leads to an increased metabolic rate, a high rate of heart beat and wasting away of the tissues of the body.
The apparent symptoms are:

1. Goitre (Swelling in the neck).
2. Protuberance of the eyeballs.
3. The patient feels tired, nervous and restless.

Iodine is essential for the production of thyroxin by the thyroid gland. The people living in hilly regions receive insufficient iodine in their diet, due to the fact that they drink iodine deficient water from rivers and streams fed by melting snow. Even their diet has little or no iodine. When there is a deficiency of iodine in the diet the thyroid gland enlarges in order to compensate for this deficiency resulting in goitre.

The thyroid gland is also called as nature gland because it secretes thyroxin hormone which is mainly responsible for the normal behaviour of human beings. In adequate supply of hormones human behaviour remains normal. In case of excess supply of hormones in the blood there are increased metabolic activities, raised nervous excitability and increased physical activity accompanied by fatigue and loss of weight.

(i) Goiter
(ii) The thyroid gland enlarges due to deficiency due to deficiency of iodine in the diet.
(iii)
1. Cretinism in children
2. Myxoedema
(iv) Thyroxin
(v) It is located in a mid-ventral position in the posterior part of the pharynx.
(vi) Thyroid-stimulating hormone/TSH.

An endocrine gland is one which does not pour its secretions into a duct, while an exocrine gland is a gland which pours its secretions into a duct. Because the pancreas produces hormones such as insulin, glucagon and somatostatin directly into the blood and not into a duct, it functions as an endocrine gland. Because it secretes the pancreatic juices for digestion via a duct, it functions as an exocrine gland. Hence, the pancreas is an exo-endocrine gland.

(i)
1. Pituitary,
2. Thyroid
3. Adrenal,
4. Pancreas,
5. Ovary.
(ii) Thyroxine.
It regulates the basal metabolism.
(iii) Islets of LangerhAnswer:
(iv) Adrenalin.
It prepares the body for some emergency by causing the production of glucose from glycogen in the liver, and releasing it into the blood.

(i)
1. Pituitary,
2. Thyroid
3. Adrenal,
4. Pancreas,
5. Ovary.
(ii) Thymus, Parathyroid.
(iii) Pancreas.

(1) Pituitary
(2) Parathyroid
(3) Hypothalamus
(4) Thyroid
(5) Thymus
(6) Adrenal
(7) Pancreas
(8) Ovaries
(9) Tests

(i)
1. Larynx.
2. Left lobe of the thyroid gland.
3. Trachea (windpipe).
4. Oesophagus.
5. Parathyroid glands.
(ii) Structure (2) secretes thyroxin hormone and structure (5) secretes parathormone.
(iii) Enzymes; which constitute the enzyme system of the body.
(iv) Hormones may be proteins, amino acids or steroids.
(v) Iodine is related to the functioning of glands (2) calcium, phosphorus is related to the functioning of the gland (5).