- Biology Notes for UPSC IAS Prelims (Part II)
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- Biology - Endocrine System
- Biology - Endocrine Diseases
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- Organisms & their Chromosome Counts
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Biology - Endocrine System
Introduction
The endocrine system is study of the glands of an organism that secrete hormones directly into the circulatory system.
The organs through which the life running hormones are secreted are known as endocrine glands or simply ductless glands.
The hormone secreting glands are located in different parts of a human body (see the image given below).
The scientific study of the endocrine system and its disorders is known as endocrinology.
Hormone
The hormone is a complex but very important chemical substance released by the different glands in the body.
The hormone is mainly made up of amino acid, catecholemines, and steroids.
It is the hormone which is responsible for the overall growth and development; safety and security; behavior, sexual characteristics, and reproductive activities of a human body.
Types of Endocrine System
Following are the major types of endocrine system −
Hypothalamus
Pineal Gland
Pituitary Gland
Thyroid Gland
Parathyroid Gland
Adrenal Gland
Pancreas Gland
Reproductive Gland (Ovaries & Testes Glands)
Let’s discuss these glands in brief −
Hypothalamus
It is located at the base of the brain.
It releases Growth hormone-releasing hormone, Somatostatin hormone, etc., important for the growth.
Pineal Gland
It is located at the base of the brain.
It releases melatonin hormone helpful in lowering the core body temperature.
Pituitary Gland
With the size of a pea, the pituitary gland is found at the base of the human brain.
The average weight of pituitary gland is about 0.5 grams.
It is also known as hypophysis.
Following are the hormones secreted by the pituitary gland −
Growth hormone (somatotropin) − It is abbreviated as GH and it stimulates growth and cell reproduction.
Thyroid-stimulating hormone (thyrotropin) − It is abbreviated as THS and it stimulates iodine absorption by thyroid gland.
Adrenocorticotropic hormone (corticotropin) − It is abbreviated as ACTH and it stimulates corticosteroid and androgen.
Beta-endorphin − it inhibits perception of pain.
Prolactin − it stimulates milk synthesis and release from mammary glands.
Thyroid Gland
Thyroid gland is located just below the larynx in the throat (pharynx).
The hormone secreted by the thyroid gland is known as thyroxine.
Following are the important hormones secreted by the thyroid gland −
Triiodothyronine(T3) − It stimulated body oxygen and energy consumption. It also promotes protein synthesis.
Thyroxine − It increases the basal metabolic rate.
Calcitonin − It stimulates osteoblasts and bone construction.
Parathyroid Gland
It is located in the neck of a human body.
It releases parathyroid hormone that helps in regulating the amount of calcium in the blood as well as within the bones.
Adrenal Gland
Adrenal gland is found above the kidneys.
It releases the following major hormones −
Glucocorticoids − It stimulates gluconeogenesis and fat-breakdown in adipose tissue.
Mineralocorticoids − It stimulates active sodium reabsorption in kidneys.
Adrenaline − It increases the supply of oxygen and glucose to the brain and muscles.
Dopamine − It increases heart rate and blood pressure.
Enkephalin − It regulates pain.
Pancreas Gland
Pancreas gland is located in the abdominal cavity (behind the stomach).
Pancreas is a mixocrine gland, as it releases both enzymes and hormones.
It releases the following major hormones −
Insulin − It regulates the metabolism of carbohydrates, proteins, and fats.
Glucagon − It raises the concentration of glucose in the bloodstream.
Somatostatin − It inhibits release of insulin and glucagon.
Reproductive Gland
The reproductive gland is classified as Testes in Male and Ovary in Female.
Testes releases androgens (hormone) that help in strengthening muscle, increasing bone density, maturation of sex organs.
Ovary releases progesterone hormone that helps during pregnancy period.