HYPOTHALAMUS -
Hypothalamus develops from the ectoderm of the embryo.
Location and Structure. It lies below or inferior to the thalamus. The hypothalamus is connected to the anterior lobe of pituitary gland by hypophysial portal veins, however it is connected to the posterior lobe of pituitary gland mainly by axons of neurosecretory cells.
Hormones. The neurosecretory cells (neurons) of hypothalamus secrete hormones called neurohormones (releasing factors).
(i) Adrenocorticotropic Releasing hormone (ARH) - It stimulates the anterior lobe of the pituitary gland to secrete its adrenocorticotropic hormone (ACTH).
(ii) Thyrotropin Releasing hormone (TRH) - It stimulates the anterior lobe of the pituitary gland to secrete its thyroid stimulating hormone (TSH) or thyrotrophin.
(ill) Somatotropin Releasing hormone (SRH) - It stimulates the anterior lobe of the pihlitary gland to release its growth hormone (GH) or somatotropin.
(iv) Growth Inhibiting hormone (GIH) somatostatin (SS) - It inhibits the secretion of growth hormone from the anterior lobe of the pituitary gland.
(v) Gonadotropin Releasing hormone (GnRH) - It stimulates the anterior lobe of the pituitary gland to secrete two gonadotropic hormones: (follicle stimulating hormone (FSH) and luteinising hormone (LH).
(vi) Prolactin Releasing hormone (PRH) - It stimulates the anterior lobe of the pituitary gland to secrete its prolactin.
(vii) Prolactin Inhibiting hormone (PIH) - It inbihits the secretion of prolactin from the ante rior lobe of pituitary gland. (viii) Melanocyte Releasing hormone (MRH) - It stimulates the intermediate lobe of the pituitary gland to secrete its melanocyte stimulating hormone (MSH).
(ix) Melanocyte Inhibiting hormone (MIH) - It inhibits the secretion of melanocyte stimulating hormone from the intermediate lobe of the pituitary gland.
Target Cells. Neurohormones act on the cells of the pituitary gland.
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Releasing of Inhibiting Hormones
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Control and Regulation of Specific Hormones
Secretion
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Thyrotropin releasing hormones (TR H )
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Stimulates thyrotropin stimulating hormone release
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Growth hormone releasing hormone (G H R H )
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Stimulates growth hormone release
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Growth hormone inhibiting hormone (G H IH )
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Inhibits growth hormone release
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Gonadotropin releasing hormone (G nR H )
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Stimulates release of follicle stimulating hormone and luteinising hormone
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Prolactin re leas in g horm one (P R H )
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Stimulates prolactin release
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Prolac tin inhibiting horm one (P IH )
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Inhibits prolactin release
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Adrenocorticotropic hormone releasing hormone
(CRH)
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Stimulates adrenocorticotropic hormone
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Melanocyte stimulating hormone releasing hormone (M R H)
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Stimulates melanocyte stimulating hormone release
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Melanocyte stimulating hormone inhibiting hormone (M IH )
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Inhibits melanocyte stimulat ing hormone release
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