Homeostasis hypothalamus role

As its name suggests, the hypothalamus lies beneath the thalamus and above the pituitary gland. Although it is quite small, accounting for only about 4 g of the total 1400 g of the adult human brain, it plays a vital role in maintenance of homeostasis in the body. It is composed of numerous cell groups and fiber pathways, each with a specific function. 

Cortisol also plays a role in controlling the release of CRH and ACTH from the hypothalamus and pituitary, respectively. As illustrated in Figure 29-2, the relationship between plasma cortisol and CRH and ACTH release is a classic example of a negative feedback control system. Increased plasma cortisol levels serve to inhibit subsequent release of CRH and ACTH, thus helping to maintain homeostasis by moderating glucocorticoid activity. 

Serotonin. Serotonin central receptors appear to play a major role in glucose homeostasis. Experiments in obese mice have demonstrated that small doses of a classical serotonin agonist, metachlorophenylpiperazine (mCPP), markedly lower plasma insulin levels and increase insulin sensitivity, without affecting food intake, body weight or fat mass. The downstream target of the involved serotonin receptor appears to be melanocortin-4 receptors, in the arcuate nucleus of the hypothalamus. 

Above the brain stem is the hypothalamus and thalamus, which together make the diencephalon. The hypothalamus is a small structure that plays an extremely important role in many aspects of emotion, motivation and response to stress. It has centres that control eating, drinking and sexual behaviour. It also regulates the autonomic nervous system and (through the pituitary gland) the endocrine system and maintains homeostasis. 

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