The hypothalamus is located below the thalamus and forms parts of the lower walls and floor of the third ventricle. It contains several nuclei that regulate a variety of critical functions including the autonomic nervous system, anterior pituitary hormone secretion, body temperature, food/water intake, and circadian rhythms. Damage to different hypothalamic regions can lead to disorders such as obesity, emaciation, diabetes insipidus, and temperature dysregulation.

1. Hypothalamus
Madanmohan and Jai Ganesh
Department of Physiology, MGMC & RI

2. Hypothalamus: introduction
• Below thalamus
• Forms lower lateral wall and floor of 3rd ventricle
• Each side:
preoptic, supraoptic, tuberal and mammillary
areas
• Many smaller nuclei, diverse functions.

3. Learning objectives
• Name the nuclei of hypothalamus.
• Name their afferent and efferent connections.
• Briefly describe the role of hypothalamus in regulation of:
1. autonomic nervous system and homeostasis
2. secretion of hormones of anterior pituitary
3. body temperature
4. food intake
5. water intake
• State the causes and consequences of disordered
hypothalamic function

5. Location of hypothalamus

6. Nuclei of hypothalamus

8. Hypothalamus: functions
1. Cyclic phenomena, biological clock:
circadian (24 h) rhythm, e.g. sleep-wake cycle.
2. Autonomic nervous system, visceral function.
3. Endocrine: anterior pituitary – releasing Hs
posterior pituitary hormones
4. Emotional, reproductive and maternal behavior.
5. Regulation of body temperature.
6. Regulation of food and water intake.

9. Circadian (24 h) rhythms
Suprachiasmatic nucleus:
endogenous biological clock
Sleep-wake cycle.
Ventrolateral preoptic area: facilitates sleep
Posterior hypothalamus: waking centre

10. Autonomic control
Head ganglion
Anterior hypothalamus: parasymp. responses
Posterior hypothalamus: symp. responses
Regulation of visceral functions: homeostasis

11. Endocrine function
Ant. pituitary releasing & inhibiting hormones:
CRH
GHRH
GHIH
TRH
PRH
PIH
GnRH
Post. Pituitary: ADH, oxytocin

12. Motivation and emotional behaviour
Principal outlet for effects of limbic system
Fear and rage
Reward and punishment areas

13. Regulation of body temperature
Heat gain Heat loss
Anterior hypothalamus
(exposure to heat)
Posterior hypothalamus
(exposure to cold)
Cutaneous vasodilatation
Sweating, hyperventilation
heat production
Cutaneous vasoconstriction
Release of CAs, TSH
activity, hunger
Shivering

14. Regulation of food intake
Lateral
feeding centre
Food intake
Ventromedial
satiety centre
Increase in
glucose

15. Regulation of water balance

16. Hyperosmolarity Hypovolemia
Angiotensin II
Subfornical organ
Osmoreceptors
(supraoptic)
Thirst + ADH
Increased water intake Decreased urinary volume
Osmolarity restored Blood volume restored
Regulation of water balance
Preoptic area

17. Disorders/syndromes
Etiology: infection, vascular, tumors, compression.
• Narcolepsy: sleep disorder
• Endocrine: diabetes insipidus, sexual disorders.
• Lesion of VM satiety centre: obesity.
• Lesion of lateral feeding centre: emaciation.
• Temperature regulation.

18. Hypothalamus: summary
• Small area, many nuclei, diverse functions.
• Regulates cyclic phenomena: sleep-wake cycle.
• Controls autonomic functions.
• Neuro-endocrine integration.
• Regulates food and water intake.
• Regulates body temperature.
• Regulation of many functions: homeostasis.
• Disordered function:
infection, tumors, compression, vascular