Hormones and the endocrine system

Hormones and the endocrine system

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  Animal hormone  Isa chemical signal that is secreted into the circulatory system and communicates regulatory messages within the body. Hormones may reach all parts of the body  But only certain types of cells, target cells, are equipped to respond
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  Endocrine Glands
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  HypothalamusGland
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   It mainlysecretes two hormones : • Releasing Hormones • Inhibiting Hormones  Hypothalamus provides connection between nervous and endocrine system.  It is also called as control centre or Supreme commander of endocrine system.
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  Pituitary Gland
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   The AnteriorPituitary or Adenohypophysis  It secrets various hormones :  Growth Hormone : It promotes growth and development of bones and muscles.  Thyroid stimulating hormone(TSH) : It stimulates the Thyroid Gland to secrete thyroxin.
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   Gigantism- Over secretionof somatotropin before puberty.  Dwarfism- Under secretion of somatotropin. Cause: tumor, injury, infection, genetics.
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   Follicle StimulatingHormone (FSH) : It stimulates the production of gametes.  Luteinizing Hormone : It stimulates the production Hormones.
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  The Posterior Pituitaryor Neurohypophysis  It secrets various hormones :  Oxytocin: It is also known as birth hormones. It stimulates the contraction and relaxation of muscles during child birth.
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   Vasopressin :it regulates water and electrolyte balance in the body by promoting reabsorption of water in the kidneys.
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  Thyroid Gland  Position: In the neck region
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  It secretes twohormones :  Thyroxin  Calcitonin  Thyroxin contains iodine and controls the metabolism of carbohydrates, fats and protein.  Calcitonin lowers the calcium levels in bones.
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  Hyperthyroidism, excessive secretion ofthyroid hormones  Can cause Graves’ disease in humans Goiter – Lack of Iodine
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  Position : Roofof the brain Hormone : Melatonin Functions : Lightens Color, regulates working of Gonads. It regulates the Biological Clock Pineal Gland
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  Pancreas  It isthe only hetrocrine gland.  It mainly secretes two hormones :  Glucagon Is produced by alpha cells  Insulin Is produced by beta cells Over secretion : Hypoglycemia Under secretion: Diabetes mellitus
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  The Adrenal Gland Position : Top of the kidneys  Are actually made up of two glands: the adrenal medulla and the adrenal cortex
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  The adrenal medullasecretes epinephrine or adrenaline and nor epinephrine or noradrenaline  Adrenaline is a emergency hormone. Adrenal Cortex secretes : 1) Mineralocorticoids 2) Glucocorticoids
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  The Gonads –Testes and Ovaries  Testes • Position : In scrotal Sacs • Hormones : Testosterone stimulate the development of secondary sexual characters in males.
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  OVARIES  Position :Lower Abdomen  Hormones : 1. Oestrogen 2. Progesterone 3. Relaxin Functions : 1. Oestrogen : Develop female reproductive organs and secondary sexual characters. 2. Progesterone : It stop egg production and attach foetus to uterine wall. 3. Relaxin : Widening of pelvis at birth.
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