All_Endocrine_New

All_Endocrine_New - ENDOCRINE SYSTEM • Endorine system...

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Unformatted text preview: ENDOCRINE SYSTEM • Endorine system and nervous system are the two main control & integration system of the body.The two systems are linked through the hypothalamus. • Hypothalamus controls secretion of many glands. Nervous &Endocrine Systems inter-relation • The nervous and the endocrine systems are inter-related in the hypothalamus through the: • The hypothalamo-hypophyseal tract . • The hypothalamo- hypopheseal –portal circulation . Control of hormone secretion • I- Nervous control : through the hypothalamus. • 2- Freed back control : * -Ve feed back. * +Ve feed back. The Principle Endocrine Glands Are :- • 1. Pituitary gland (anterior & posterior) • 2. Thyroid gland. • 3. Parathyroid gland. • 4. Suprarenal or adrenal gland (cortex & medulla) • 5. Islets of langerhans ( in the pancreas) • 6. Male gonads ( testes) & Female gonads • 7. Placenta. Endocrine Glands Other Endocrine Organs :- 1. The kidney secrete : a) renin b)Erythropoietin, c)1.25 dihydroxy cholecalciferol, d) Certain Prostaglandin. 2. The Heart :Rt. Atrium secretes Atrial Natriuretic Peptide. 3. Local hormones secreted at :- GIT,-Chemical transmitters, released by nerve endings. • Are chemical substances sythesized & secreted by specific cells, they are transported by the circulation at very low concentration .It elicits a specific response in distant target tissues. Hormones Forms of Hormones in the Blood 1- Free. * It is not carried on a plasma protein . * It can bind directly to the receptors : active . * It is small in size , so can be filtered in urine . 2- protein bound . * Carried on plasma protein . * It acts as a reservoir. * It increases the half life of the hormone. * It is more soluble in plasma ( the lipid steroids , when bound to plasma proteins they are transformed into water soluble. * It is large in size , and so is not filtered in urine . Hormone Transport & inactivation • Water insoluble hormones : Steroid & thyroxin are bound to plasma proteins in blood stream. Only free hormones ( not in bound form ) can affect its target cells. Inactivation in liver by : degradation oxidation reduction methylation Conjugation to glucoronic acid Then excreted in : urine. Hormone Receptors &their activation : . Hormone never act directly. . They combine with Specific recaptors . . Receptors are large protein molecules , they are . Present either : On the surface of cells or inside the cells cytoplasm or in. nucleus. LOCATIONS Receptors of protein, peptide hormones& catecholamines located in the membrane . Receptors of steroid hormones located in cytoplasm . Receptors of thyroxin located in nucleus . Mechanism of action of hormones which are protein in nature 1-On cell membrane of target cell .:hormone combines with its specific receptor....
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This note was uploaded on 12/21/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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All_Endocrine_New - ENDOCRINE SYSTEM • Endorine system...

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