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Hypothalamus
The hypothalamus is the basal part of the diencephalon (forebrain), regulating a broad spectrum of body functions. The hypothalamus contains several neurosecretory cells called nuclei, which produce neurohormones. The hormones from the hypothalamus control the production and release of pituitary hormones. Two types of hormones are produced by the hypothalamus: releasing and inhibiting hormones. These hormones control the production and release of pituitary hormones
Gonadotrophin-releasing hormone (GnRH), produced by the hypothalamus, stimulates the pituitary gland to produce and release gonadotrophins. Conversely, somatostatin, also produced by the hypothalamus, prevents the pituitary gland from releasing growth hormones. These hormones travel through axons and are released from nerve endings in the hypothalamus. They then reach the anterior pituitary through a portal circulatory system and regulate its functions. The posterior pituitary is directly regulated by the hypothalamus.
1.0Structure of Hypothalamus
It is a complex structure located below the thalamus. It consists of several nuclei, which are groups of nerve cells or neurons. Hypothalamus nuclei are located within specific regions & zones (Regions → preoptic, mammillary, tubular, supraoptic)
(Zones → Periventricular, intermediate, lateral)
2.0Parts of Hypothalamus
- Mammillary region (mammill = nipple shaped) : Adjacent to the midbrain, and the most posterior part of the hypothalamus. It includes the posterior hypothalamic nuclei & mammillary bodies.
- Function: Increase b.p., pupillary dilation, memory, sleep etc.
- Tuberal region : This region is present in the middle and widest part of the hypothalamus and includes the lateral nucleus, dorsomedial nucleus, ventromedial nucleus, and arcuate nucleus.
- A stalk-like infundibulum is present, which connects the pituitary gland to the hypothalamus..
- Function = GI stimulation, neuroendocrine control, blood pressure, GHRH etc.
- Supraoptic region : (Supra = above, optic eye) It lies superior to the optic chiasm & present in the anterior region. It includes preoptic nucleus, suprachiasmatic nucleus, supraoptic nucleus, paraventricular nucleus and anterior hypothalamic nucleus.
- Function = Thermoregulation, regulates the release of gonadotropic hormones, sweating, circadian rhythms etc.
- The Preoptic region : Anterior to the supraoptic region is usually considered part of the hypothalamus. It regulates certain autonomic activities. It include medial & lateral preoptic nuclei.
3.0Functions of Hypothalamus
- Regulation of circadian rhythms & state of consciousness
- Regulation of eating & drinking
- Regulation of emotional & behavioral pattern
- Control of body temperature
- Control of ANS
- Production of hormones
- Motor function check
- Maintaining sleep cycles
Hormones of the Hypothalamus: Releasing and inhibiting hormones are produced in hypothalamic nuclei and then transported along axons to the median eminence.
4.0Disorders of Hypothalamus
- Infertility
- Diabetes insipidus
- High and Low B.P
- Insomnia/sleep disorders
- Fluctuations in appetite & thirst
- Hypothalamus tumors
- Excessive thirst & urination