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HORMONE OF POST. PITUITARY GLAND

HORMONE OF POST. PITUITARY GLAND . 1-Vasopressin 2- Oxytocin Each is composed of a.a , both hormones are produced in hypothalamus and flow to nerve endings in post. Pituitary gland to be stored, they are type I and II synthesized with ox toxin and vasopressin respectively.

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HORMONE OF POST. PITUITARY GLAND

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  1. HORMONE OF POST. PITUITARY GLAND

  2. 1-Vasopressin • 2-Oxytocin • Each is composed of a.a, both hormones are produced in hypothalamus and flow to nerve endings in post. Pituitary gland to be stored, they are type I and II synthesized with ox toxin and vasopressin respectively. • Vasopressin (ADH) is primarily synthesized in supra Optic nucleus and oxytocin in paraventicular nucleus

  3. Each has 9 a.a containing cysteins molecules at position 1and 6 linked by s-s bridge , most animals have arginine vasopressin while in pigs and related species has a lysine vasopressin substituted in position 8 . Cys-Tyr- Phe - Glu - Asn - Cys -Pro- Arg-Gly-NH2 Arginine vasopressin (in human) Cys-Tyr- Phe - Glu - Asn - Cys -Pro- Lys-Gly-NH2 Lysine Vasopressin Cys-Tyr- Ile- Glu - Asn - Cys -Pro- Arg-Gly-NH2 Oxytocin

  4. Oxytocin • The neural impulses that result from the stimulation of the nipple are the primary stimulus for oxytocin release. Vaginal and uterine distention are secondary stimuli . • The mechanism of action is unknown but it cause contraction of uterine smooth muscle and used in pharmalogic amount to induce labour in human . Also it stimulate contraction of myoepithelial cells surrounding the mammary alveoli and help ejection of milk.

  5. Membrane-receptor for oxtocin present in uterine and mammary tissue, these receptors increased in number by estrogen and decreased by progesterone . • ADH • The neural impulse that trigger ADH release are activated by increase osmolality of plasma is mediated by osmoreceptors located in the hypothalamus and by baroreceptors located in heart and other regions of the vascular system. Other stimuli include emotional . Physical stress , drugs as morphine , nicotine, epi , but ethanol inhibit its secretion. • ADH exert its effect on convoluted distal tubules

  6. And collecting duct-Kidney. • The receptor is linked to adenylate cyclase and cAMP mediate its effect. • Secretion of AVP, is stimulated by • 1- increased plasma osmolality via hypothalamic osmoreceptors. • 2- Severe blood volume depletion via cardiac baroreceptors . • 3- Stress and nausea. • AVP causes water to be retained by the kidneys . Fluid deprivation results in the stimulation of endogenous AVP secretion which reduces the urine flow rate to as little as 0.5ml/min in order to conserve body water. However , within an hour of drinking 2 litres of water , the urine flow rate may rise to 15ml/min as AVP secretion is shut down.

  7. AVP maintains normal electrolyte concentrations within the body. • Deficiency of ADH • 1- Primary Diabetes insipidus . • 2- Secondary Diabetes insipidus .

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