Physiology of hypothalamus
- 1. PHYSIOLOGY OF HYPOTHALAMUS Dr. REVAND R. IMS-BHU Varanasi
- 2. At the end of the class students will be able to • Point out the location of hypothalamus in the brain • Enumerate the various nuclei of physiological importance present in the hypothalamus • Describe the various functions of hypothalamus along with their mechanisms in brief • Clinically comprehend lesions involving hypothalamus
- 3. Clinical case:1 16-year-old girl was taken by her mother to a pediatrician because she was rapidly losing weight. The mother stated that the weight loss started about 1 year ago. The child's eating habits had changed from eating practically anything put before her to being a very choosy eater. Her personality had also changed, and she feared meeting strangers. On being urged to eat more food, the girl countered by saying she was getting fat and must diet to improve her figure. Although she would not admit to having anything wrong with her, she admitted that menstruation had ceased 3 months previously.
- 4. Clinical case:1 (continued) On being questioned by the pediatrician, the girl admitted to calorie counting, and sometimes, when she felt she had overeaten, she went to the toilet and forced herself to vomit by sticking her fingers down her throat. On physical examination, she showed obvious signs of weight loss with hollow facial features, prominent bones, and wasted buttocks. Apart from having cold extremities and a low blood pressure of 85/60 mm Hg, no further abnormalities were discovered.
- 5. Clinical case:2 A 17-year-old boy was admitted into the medical ward with 3-month history of severe headaches. More recently, he had had attacks of vomiting and 1 week ago he had noticed problems with his eyesight. The patient said that he had difficulty seeing objects on the lateral side of both eyes. His parents were concerned that he was putting on weight, as he was especially fat over the lower part of the trunk. On physical examination, the boy was found to be 6 feet 3 inches tall; he had excessive trunk obesity. The testes and penis were small and pubic and axillary hair was absent. What is wrong with the patient?
- 8. • Located below the thalamus • Forms the inferior part of the lateral wall of the third ventricle • Lies posterior to the optic chiasm
- 9. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 10. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 11. Three – hormone sequence Stimulating hormone (Tropic hormone) Releasing hormone (hypophyseotropic hormone) Hormone
- 12. Hypothalamo – hypophyseal portal system • Portal system starts in the median eminence • Releasing hormones reach anterior pituitary via blood capillaries • Anterior pituitary hormones are also released into the blood capillaries
- 13. Advantages of portal system • Hypophyseotropic hormones reach anterior pituitary without delay • Small volumes of hypophyseotropic hormones do not dilute in the larger volumes of systemic circulation as it remains confined to the portal circulation • Volume of hypophyseotropic hormones reaching the general circulation is very low reducing unnecessary side effects systemically • The flow of blood is very slow in the portal vessels. This allows the small volumes of hypophyseotropic hormones to concentrate in the portal circulation and delivered to the anterior pituitary (amplification)
- 14. Medial eminence is outside blood – brain barrier • Hypothalamic hormones can be directly emptied into blood • Osmoreceptors directly detect the change in the osmolality of blood, helping in regulation of blood volume and water intake • Regions located outside BBB are: Organum vasculosum of lamina terminalis (OVLT) Sub – fornicial organ (SFO) Area postrema
- 15. HYPOTHALAMIC NUCLEI MED. EM. ANT. PIT. POST. PIT. ANT.HY.N. POST.HY.N. HHPORT.SYS. SYSTEMIC CIRC.
- 17. “In – sequence” feedback regulation +
- 18. “Non – sequence” regulation of pituitary hormones
- 19. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 20. Posterior pituitary secretions • Two neurophysins – preprooxyphysin and prepropressophysin • Produced by magnocellular neurons of hypothalamus
- 21. PARAVENTRICULAR NUCLEI POST. PIT. POST.HY.N. SYSTEMIC CIRC. c c c cc Contraction of myoepithelial cells Contraction of uterine smooth muscles
- 22. SUPRAOPTIC NUCLEI POST. PIT. POST.HY.N. SYSTEMIC CIRC. c c c cc ANT. HYPOTH. Angiotensin II binds to SFO and OVLT Incorporate aquaporins in DCT and CT Vasoconstriction V1 receptor Activates phospholipase C; hydrolyses PIP; increase Ca V2 receptor Activates adenylyl cyclase – cAMP ; increase Ca Move endosomes containing aquaporins in DCT and CT Increase water reabsorption
- 23. Oxytocin and vasopressin secretion - variations • Stimulation of the nipples causes a synchronous (same time in all neurons secreting oxytocin), high-frequency discharge of the oxytocin neurons. This discharge causes release of a pulse of oxytocin and consequent milk ejection in postpartum females. • Stimulation of vasopressin-secreting neurons by a stimulus such as an increase in blood osmolality or loss of blood volume, causes an asynchronous initial steady increase in firing rate followed by a prolonged pattern of phasic discharge in which periods of high- frequency discharge alternate with periods of electrical quiescence (phasic bursting). Phasic bursting is well-suited to maintain a prolonged increase in the output of vasopressin needed for correction of the water imbalance
- 24. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 25. ANTERIOR HYPOTHALAMUS Angiotensin II binds to SFO and OVLT CAROTID BODY and AORTIC ARCH ADH secretion Reduce water loss Dryness of mouth and throat Metering of water intake by GIT
- 26. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 27. Lateral hypothalamus (Feeding centre) Feeding Ventromedial Hypothalamus (Satiety centre) Blood glucose Glucoreceptors (Glucostats) Neuropeptide Y, Orexin A and B, Ghrelin Free fatty acids, Leptins, CCK
- 28. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 29. Anterior hypothalamus Heat loss Posterior hypothalamus Heat gain High body temperature sensed by central and peripheral receptors Low body temperature sensed by central and peripheral receptors Cutaneous vasodilation, sweating (37°C) Cutaneous vasoconstriction (36.8 °C), shivering (35.5 °C)
- 31. MCQ : 1 Choose the correct statement with respect to temperature regulation A. The thalamus integrates information regarding temperature regulation B. Fever is caused by the action of prostaglandins on hypothalamus C. Shivering is a mechanism of heat gain on prolonged exposure to cold D. When the body temperature is above the set point temperature, heat gain is more than heat loss E. Sweating occurs as a response to external temperature > 37 ° C
- 32. MCQ : 1 (discussion) Choose the correct statement with respect to temperature regulation A. The thalamus integrates information regarding temperature regulation B. Fever is caused by the action of prostaglandins on hypothalamus C. Shivering is a mechanism of heat gain on prolonged exposure to cold D. When the body temperature is above the set point temperature, heat gain is more than heat loss E. Sweating occurs as a response to external temperature > 37 ° C
- 33. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 34. Retina Supra chiasmatic nucleus Sleep – wake cycle (Biological clock) Diurnal variation of hormonal secretions Retino–hypothalamic tract Reticular activating system Mammillary body Pineal gland Nocturnal secretion of melatonin WAKE SLEEP Mammillo – tegmental tract
- 35. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 36. Papez circuit Anterior nucleus of thalamus Cingulate gyrus Hippocampus Hypothalamus Mammillary body Prefrontal cortex Brainstem nuclei Fornix Mammillo-thalamic tract of Vicq d’Azur MemoryMotivation AmygdalaStria terminalis
- 37. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 39. Functions of hypothalamus 1. Regulation of activity of anterior pituitary gland 2. Formation and regulation of secretion of posterior pituitary hormones 3. Control of water intake 4. Control of hunger and feeding 5. Regulation of body temperature 6. Control of circadian rhythm and sleep – wake cycle 7. Control of emotional behaviour 8. “Head ganglion” of autonomic nervous system
- 40. HYPOTHALAMIC NUCLEI – CLASSIFICATION
- 41. Hypothalamic nuclei Anterior LateralMedial Supra chiasmatic Anterior Posterior Mammillary body Preoptic Supra optic Ventromedial Dorsomedial Infundibular Paraventricular
- 42. Hypothalamic nuclei Anterior LateralMedial Supra chiasmatic Anterior Posterior Mammillary body Preoptic Supra optic GnRH Osmoreceptors Heat loss ParasympatheticEmotions GnRH Fever origin Parasympathetic Vasopressin Somatostatin Biological clock
- 43. Hypothalamic nuclei Anterior LateralMedial Posterior Ventromedial Dorsomedial Infundibular Paraventricular TRH GHRH TRH CRH Oxytocin Satiety
- 44. Hypothalamic nuclei Anterior LateralMedial Posterior Feeding Sympathetic Heat gain Sympathetic
- 45. Hypothalamic nuclei Anterior LateralMedial Supra chiasmatic Anterior Posterior Mammillary body Preoptic Supra optic GnRH Osmoreceptors Heat loss ParasympatheticEmotions GnRH Fever origin Parasympathetic Vasopressin Somatostatin Biological clock Hypothalamic nuclei Anterior LateralMedial Posterior Ventromedial Dorsomedial Infundibular Paraventricular TRH GHRH TRH CRH Oxytocin Satiety Hypothalamic nuclei Anterior LateralMedial Posterior Feeding Sympathetic Heat gain Sympathetic
- 46. Clinical case:1 (discussion) – Anorexia nervosa 16-year-old girl was taken by her mother to a pediatrician because she was rapidly losing weight. The mother stated that the weight loss started about 1 year ago. The child's eating habits had changed from eating practically anything put before her to being a very choosy eater. Her personality had also changed, and she feared meeting strangers. On being urged to eat more food, the girl countered by saying she was getting fat and must diet to improve her figure. Although she would not admit to having anything wrong with her, she admitted that menstruation had ceased 3 months previously. On being questioned by the pediatrician, the girl admitted to calorie counting, and sometimes, when she felt she had overeaten, she went to the toilet and forced herself to vomit by sticking her fingers down her throat. On physical examination, she showed obvious signs of weight loss with hollow facial features, prominent bones, and wasted buttocks. Apart from having cold extremities and a low blood pressure of 85/60 mm Hg, no further abnormalities were discovered.
- 47. Clinical case:2 (discussion) A 17-year-old boy was admitted into the medical ward with 3-month history of severe headaches. More recently, he had had attacks of vomiting and 1 week ago he had noticed problems with his eyesight. The patient said that he had difficulty seeing objects on the lateral side of both eyes. His parents were concerned that he was putting on weight, as he was especially fat over the lower part of the trunk. On physical examination, the boy was found to be 6 feet 3 inches tall; he had excessive trunk obesity. The testes and penis were small and pubic and axillary hair was absent. What is wrong with the patient?
- 49. Clinical case:2 (diagnosis) Hypothalamic mass probably tumour causing Bitemporal hemianopsia + obesity + hypogonadism Babinski – Frohlich syndrome (or) Launois – Cleret syndrome (or) Hypothalamic infantilism with obesity (or) Adiposo-genital dystrophy
- 50. THANK YOU