1. Posterior Pituitary Prof. K. Sivapalan

2. 08-01-14Hypophysis.2 Structure and Blood Supply. Posterior lobe is supplied by inferior Hypophysial artery. Neurons in the hypothalamus, endings in posterior lobe.

3. 08-01-14Hypophysis.3 Anti Diuretic Hormone [Vasopresin] 9 amino acids, 1000 mw. Half life- 18 minutes. Action in physiologic doses: –Increase water and urea permeability in collecting ducts. –Anti diuresis. Action in large doses: –Contraction of vascular smooth muscles. –Increase blood pressure.

4. 08-01-14Hypophysis.4 Control of secretion of ADH. Increased osmolality stimulates osmoreceptors in hypothalamus and increases secretion. Increased blood volume stimulates volume receptors in IVC and Left atrium, inhibits secretion.

5. 08-01-14Hypophysis.5 Other Factors influencing ADH. Stimulation: Increase of OP of plasma. Decreased ECF volume. Pain, emotion, stress, exercise. Nausea and vomiting. Standing Angeotensin II Carbamazapine, clofibrate Inhibition: Decreased Osmotic pressure. Increased ECF volume. Alcohol.

6. 08-01-14Hypophysis.6 Abnormal Secretion. Excess- water intoxication. –Reduced plasma osmolality. –Dilutional hyponatreamia. ? Drinking water after surgery, child birth etc. Insufficiency- diabetes Insipidus. –Polyurea and polydepsia.

7. 08-01-14Hypophysis.7 Oxytocin. 9 Amino acids. Synthesized in hypothalamus and released in Post. Pituitary.

8. 08-01-14Hypophysis.8 Actions of Oxytocin. Contraction of myo- epithelial cells of the breast. Contraction of pregnant uterus –Enhanced by estrogen –Inhibited by progesterone. ?facilitate sperm trans port and fertilization Contraction of Vas deferens during ejaculation.

9. 08-01-14Hypophysis.9 Stimulation of Secretion. Stimulation of nipple- milk ejection reflex. Stretch of cervix of the uterus- parturition Sexual stimulation.

10. 08-01-14Hypophysis.10 Inhibition of Oxytocin Secretion. Alcohol Stress. Pain Discomfort. Embarrassing conditions. Fear Anger.