Test: Endocrine Glands and Human Endocrine System (October 5) - NEET MCQ

Endocrine glands are ductless glands of the endocrine system that secrete their products, hormones directly into the blood. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands.

The pituitary gland is a tiny organ, the size of a pea, found at the base of the brain. As the “master gland” of the body, it produces many hormones that travel throughout the body, directing certain processes or stimulating other glands to produce other hormones.

ANF (atrial natriuretic factor) is secreted by the atrial walls of the heart. It is responsible for a decrease in blood pressure. When the blood pressure is increased, ANF which is secreted dilates the blood vessels causing a decrease in blood pressure.

• Erythropoietin is a  peptide hormone produced primarily by juxtaglomerular cells of the kidney.
• Erythropoietin stimulates the bone marrow to produce more red blood cells.
• The resulting rise in red cells increases the oxygen-carrying capacity of the blood.
• As the prime regulator of red cell production, erythropoietin's major functions are to promote the development of red blood cells.
• Hence, Juxtaglomerular cells of kidney produce a peptide hormone called Erythropoietin.

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.

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.

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

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.