Summary PHYSIOLOGY : Hypothalamic Hormones

Hypothalamic Hormones Overview • General Anatomy • Hormones produced • Actions of hormones • Regulation of hormone secretion • Abnormalities of secretion General Anatomy • The hypothalamus is named so because it lies under the thalamus(‘hypo’ means ‘under’) • It is found in the diencephalon. • It is located inferior to the thalamus, posterior to the optic chiasm and bordered on the sides by the temporal lobes and optic tracts. • It is almond shaped and weights about 4 grams. • The hypothalamus is connected to the posterior pituitary via the infundibulum. • Its close proximity and its interactions with the thalamus and pituitary gland enables it to act as a bridge between the nervous and endocrine system. • In the hypothalamic – adenohypophyseal axis releasing hormones ( hypothalamic hormones) are released from median eminence, a prolongation of the hypothalamus into the hypophyseal portal system which carriers them to the anterior pituitary where they exact their regulatory functions on the section of adenohypophyseal hormones. • This hypophysiotropic hormones an stimulated by parvocellular neuroscretory cells located in the periventricular area of the hypothalamus. • The hypophysiotropic hormones travel through hypothalamus pituitary portal circulation. These hormones bind to specific receptors located on the surface of pituitary cells. • Depending on which cells an activated, the pituitary will either begin secreting or stop secreting hormone. • In the hypothalamic – neurohypophyseal axis, neurohypophyseal hormones are released from the posterior pituitary. • These hormones are secreted from the median eminence of the hypothalamus. • Thyrotropin Releasing Hormone • Gonadotropin Releasing Hormone • Corticotropin Releasing Hormone • Growth Hormone Releasing Hormone • Growth hormone Inhibitory Hormone • Dopamine • Anti Diuretic Hormone • Oxytocin • The releasing hormones and inhibiting hormones are released into capillaries and travel immediately in portal veins to a second capillary bed in the anterior lobe of pituitary gland where they exert their function. • Vasopressin and oxytocin travel in neurons themselves to posterior lobe of pituitary where they are released into circulation