Chemical Coordination and Integration Test 15

Endocrine system, like the nervous system, is meant for internal communication and regulation of the animal body. These two systems operate in a coordinated way on many occasions. Many important functions of the endocrine system are infact, under the control of nervous system. Therefore, the two systems are often collectively called as neuroendocrine system.

Endocrine glands lack ducts and pass their secretions into the surrounding blood for transport to the site of action. They are also called ductless glands. Their secretions are known as hormones.

FSH secreted by anterior lobe of pituitary gland is proteinaceous in nature. FSH stimulates growth of ovarian follicles and their secretion of estrogens in the female and spermatogenesis in the male.

Chemically, hormones are of different naturelle biogenic amines (e.g., thyroxine), proteins (e.g., hypothalamic hormones) and steroids (e.g., sex hormones).

(i) Peptides: These hormones are further of two types: Short peptide and long peptide.
Short peptide: The hormones oxytocin and vasopressin from the posterior lobe of the pituitary gland.
Long peptide: The hormones insulin and glucagon from the pancreas.
(ii) Steroid: The hormones from adrenal cortex, testes, ovaries and placenta are steroids. So, testosterone is a steroid.
(iii) Amino acid derivative: The hormones epinephrine and norepinephrine from the adrenal medulla and thyroxine from the thyroid gland are derived from the amino acid tyrosine.
So, the correct answer is '(i)- Oxytocin, (ii)- Steroid, (iii)- Iodothyronine, (iv)- Epinephrine'.

Insulin is a large popylpeptide hormone and is insoluble in lipids, therefore, it cannot enter the target cell. It acts at the cell surface. It operates through extracellular membrane bound receptor, a heterotetrameric protein (extrinsic protein) on the target cell.

Prostaglandins are hormone-like compounds derived from 20-carbon polyunsaturated fatty acids. Their richest sources are the secretion of seminal vesicles in males and menstrual fluid in females. They have variety of effects such as vasodilation, vasoconstriction, uterine stimulation etc.

Prolactin release inhibiting hormone is an amino acid derivative hormone produced in the hypothalamus.

Thyroxine is an amino acid derivative hormone.

The steroids are organic compounds involved in biological processes. Steroid hormones are generally synthesized from cholesterol in gonads and adrenal glands. They are basically lipids. For example, estrogen, progesterone, testosterone, etc.