Origin. Hypothalamus develops from the ectoderm of the embryo.
Hypothalamus Location. It is the base of the diencephalon, a part of the forebrain.
Structure of hypothalamus. The hypothalamus is composed of nervous tissue. It is connected with anterior lobe of the pituitary gland by hypophysial portal blood vessels and with the posterior lobe of the pituitary gland by axons of its neurons. The portal vessels and axons pass through a stalk to the pituitary lobes.
The neurosecretory cells of the hypothalamus, when stimulated, release hormones, called neurohormones via axons into the capillaries.The neurohormones are carried by the portal blood to the anterior lobe of the pituitary gland and stimulate the latter to release its hormones. On this account, such hypothalamic hormones are also called releaser hormones (RH). Certain hypothalamic hormones inhibit the secretion of some pituitary hormones. These are termed inhibitory hormones or factors (IH or IF). The well known releasing and inhibitory hormones of hypothalamus are described below and summarised in table –
(i) Thyrotrophin-Releasing Hormone (T-RH)
It stimulates the anterior pituitary to secrete its thyroid-stimulating hormone (TSH), or thyrotrophin.
(ii) Adrenocorticotrophin-Releasing Hormones (A–RH)
It excites the anterior pituitary to produce its adrenocorticotrophic hormone (ACTH), or adrenocorticotrophin.
(iii) Follicle-Stimulating Hormone-Releasing Hormone (FSH- RH)
It stimulates the anterior pituitary to secrete its follicle- stimulating hormose.
(iv) Luteinising Hormone- Releasing Hormone (LH-RH)
It stimulates the anterior pituitary to secrete its luteinsing hormone.
(v) Growth Hormone (Somatotrophin) –Releasing Hormone (GH-RH or S-RH)
It stimulates the anterior pituitary to release its growth hormone (GH), or somatotrophin.
(vi) Growth Hormone Release-Inhibiting Hormone (GH-RIH), or Somatostatin
It inhibits the secretion of growth hormone from the anterior pituitary.
(vii) Prolactin-Releasing Hormone (P-RH)
It stimulates the anterior pituitary to secrete its prolactin or luteotrophic hormone (LTH).
(viii) Prolactin Release-Inhibiting Hormone (PR-IH)
It inhibits the secretion of prolactin from the anterior pituitary.
(ix) Melanocyte-Stimulating Releasing Hormone – (MSH- RH)
It stimulates the intermediate lobe of the pituitary gland to release the melanocyte-stimulating hormone (MSH).
(x) Melanocyte-Stimulating Hormone Release-Inhibiting Hormone (MSH– RIH).
It inhibits the release of melanocyte- stimulating hormone from the intermediate lobe of the pituitary glands.
The hormones secreted by the posterior lobe of the pituitary gland are actually synthesized by the neurons in the hypothalamus and stored in their axon ends in the posterior lobe for release through growth the latter when required.
The hypothalamic- pituitary system is of paramount importance for homeostasis as it regųlates the most major physiological activites in the body. It also indicates a close connection and coordination between the hormonal and nervous systems. It is at this connection that the nerve impulses are translated into chemical messages.
The function of hypothalamus are releasing hormones, maintaining daily physiological cycles, blood pressure and heart rate, managing of sexual behavior, production of digestive juices and in process of memorizing and in stress control.
The hypothalamus acts as the connector between the endocrine and nervous systems to achieve this . It control balancing bodily fluids in the control of the body’s temperature and energy maintenance, and in the process of memorizing and in stress control.