Hypothalamus

Madanmohan and Jai Ganesh

Department of Physiology, MGMC & RI

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.

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

Location of hypothalamus

Nuclei of hypothalamus

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.

Circadian (24 h) rhythms

Suprachiasmatic nucleus:

endogenous biological clock

Sleep-wake cycle.

Ventrolateral preoptic area: facilitates sleep

Posterior hypothalamus: waking centre

Autonomic control

Head ganglion

Anterior hypothalamus: parasymp. responses

Posterior hypothalamus: symp. responses

Regulation of visceral functions: homeostasis

Endocrine function

Ant. pituitary releasing & inhibiting hormones:

CRH

GHRH

GHIH

TRH

PRH

PIH

GnRH

Post. Pituitary: ADH, oxytocin

Motivation and emotional behaviour

Principal outlet for effects of limbic system

Fear and rage

Reward and punishment areas

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

Regulation of food intake

Lateral

feeding centre

Food intake

Ventromedial

satiety centre

Increase in

glucose

Regulation of water balance

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

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.

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