Endocrine System - Notes, Biology, IAS UPSC Notes | EduRev

General Science(Prelims) by IRS Divey Sethi

UPSC : Endocrine System - Notes, Biology, IAS UPSC Notes | EduRev

The document Endocrine System - Notes, Biology, IAS UPSC Notes | EduRev is a part of the UPSC Course General Science(Prelims) by IRS Divey Sethi.
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Endocrine System

  • Formed by endocrine glands ( or Ductless Glands ) and their secretion.
  • They secrete hormones directly into the blood stream in response to instructions from the brain.
  • The blood then carries them around the body.

Endocrine System - Notes, Biology, IAS UPSC Notes | EduRev

 

Hypothalamus

  • Forms a part of fore – brain, secretes neurohormones, which effect the release of hormones from pituitary.
  • Acts as the thermostat.

Pituitary Gland

  • Also called Master Gland.
  • It is the smallest endocrine gland.
  • It secretes :
  • 1. Somatotrophic Hormone ( Growth stimulating Hormone ) : Controls the general growth of the body.
    • Its hypersecretion leads to acromegaly in adults and gigantism in children. Its hyposecretion leads to dwarfness in children.
  • 2. Gonadotrophic Hormone ( GTH ) : Stimulates the primary sex hormones, i.e. ovaries and testes.
  • 3. Lactogenic Hormone : Initiates milk production in the pregnant females.
  • 4. Thyrotrophic Hormone : Aids in the regulation of thyroid secretion.
  • 5. Adrenocorticotrophic Hormone ( ACTH ) : Influences the secretion from the cortex of adrenal glands.
  • 6. Diabetogenic or Metabolic hormone: influences metabolism of carbohydrates, fats and proteins.
  • 7. Oxytocin or Pitocin : Stimulates smooth muscle contractions, especially of the uterus during child birth. Also helps in the secretion of milk in females.
  • 8. Vasopressin or ADH ( Anti – Diuretic Hormone ) : Regulates reabsorption of water from the kidney tubules.
    • Its Hypoactivity leads to Diabetes insipidus in which patients excrete large amount of urine.
    • Also causes contraction of small arteries, causing increase in Blood Pressure.

Thyroid Gland

  • It is the largest endocrine gland located in the neck between the trachea and larynx.
  • Controls BMR ( Basal Metabolic Rate ).
  • BMR is minimum energy requirement for maintenance of body during rest or sleep.
  • For normal human adult, it is 1600 Kcal / day.
  • 3. Lactogenic Hormone : Initiates milk production in the pregnant females.
  • 4. Thyrotrophic Hormone : Aids in the regulation of thyroid secretion.
  • 5. Adrenocorticotrophic Hormone ( ACTH ) : Influences the secretion from the cortex of adrenal glands.
  • 6. Diabetogenic or Metabolic hormone: influences metabolism of carbohydrates, fats and proteins.
  • 7. Oxytocin or Pitocin : Stimulates smooth muscle contractions, especially of the uterus during child birth. Also helps in the secretion of milk in females.
  • 8. Vasopressin or ADH ( Anti – Diuretic Hormone ) : Regulates reabsorption of water from the kidney tubules.
    • Its Hypoactivity leads to Diabetes insipidus in which patients excrete large amount of urine.
    • Also causes contraction of small arteries, causing increase in Blood Pressure.

Thyroid Gland               

  • It is the largest endocrine gland located in the neck between the trachea and larynx.
  • Controls BMR ( Basal Metabolic Rate ).
  • BMR is minimum energy requirement for maintenance of body during rest or sleep.
  • For normal human adult, it is 1600 Kcal / day.

Thyroid Gland Secretes :

1. Thyroxine : Regulates physical, mental and sexual development.

  • Hypoactivity in children leads to cretinism. Hypoactivity in adults leads to Myxoedema ( sluggish appearance, feeble mindedness, low body temperature ).
  • A diet, poor in iodine, which is insufficient for the synthesis of thyroxin, leads to simple goitre.
  • Its hyperactivity leads to increased metabolic activities (highly nervous, overactive and irritated person).

Pancreas

  • It is an exocrine as well as an endocrine gland. Its endocrine part is known as Islets of Langerhans. Its 3 types of cells secrete 3 different hormones.
  • Beta cells secrete Insulin which controls the amount of sugar in the blood. Its hyposecretion leads to Diabetes Mellitus.
  • Alpha cells secretes Glucagon which increases blood sugar level.
  • Gamma cells secrete Somatostatin which controls the functioning of alpha and beta cells.

Adrenal Glands

  • 2, on each kidney.
  • Adrenal gland is also known as 4S gland. ( 4S stands for: Sugar metabolism, Salt retention, Sex hormone and Source of energy ).
  • Consists of 2 Distinct Parts : Outer cortex and inner medulla.
  • 1. Adrenal Medulla secretes Adrenaline or epinephrine which effects liberation of glucose from glycogen stored in liver and increases the rate of metabolism.
  • Its over – secretion leads to increased saliva flow, tears, bile and sweat, quickens heart beat, speeds up respiratory activities.
  • It is also known as 3F Gland because of these ( fear, fight, flight ).
  • Nor – epinephrine or Nor – adrenaline is also secreted from medulla (20%) which is opposite to adrenaline.

 

2. Adrenal Cortex secretes two types of Hormones :

  • Mineralo Corticoids : Maintain electrolyte balance in the body and distribution of water to the tissues.
  • It. is also known as salt retaining hormone.
  • Its hyposecretion results in Addison’s disease. In this disease, excessive loss of Na, Cl ions takes place and level of K ions increases in blood.
  • Its hypersecretion leads to retension of Na, Cl ions and more absorption of water.
  • Gluco Corticoids : It influences carbohydrate metabolism and also effect protein and fat metabolism.
  • Its hyposecretion leads to fall in glucose level due to which body temperature decreases.
  • Its hypersecretion leads to Cushing Disease in which irregular deposition of fat takes place and glucose level increases in blood

GONADS

  • Both testes and ovaries, in addition to producing sperms and ova, also produce hormones.

Testes

  • Its interstitial cells (Leydig’s cells) secrete testosterone which is responsible for male secondary sexual characters (beard, body hair, deep voice, muscles, formation of sperms, sexual urge, etc).
  • Deficiency leads to sterility (eunuchoidism).

 

Ovaries

  • In females, the follicular cells and corpus luteum secretes the following hormones :
  • Follicular Cells produces Oestrogen which controls the female secondary sexual characters (Broadening of pelvis, development of breasts, growth of uterus and vagina, pubic hair, onset of menstrual cycle, etc).
  • Corpus luteum secretes Progesterone which is essential for the completion of each menstrual cycle.
  • It controls the final changes in the uterine wall and brings about the attachment of embryo and causes development of breasts in the later months of pregnancy.
  • Corpus Luteum also secretes Relaxin at the end of gestation period, and helps in easy birth by relaxing the uterus and ligaments of the pelvic girdle.

 

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