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Unformatted text preview: Endocrine System Anterior Pituitary Gland (Adenohypophysis) * Hormone secretion regulated by * releasing hormones and inhibiting hormones from the hypothalamus * Negative feedback from hormones of target glands that act on Ant. Pit and thypothalamus Hypothalamus produces nine hormones * Seven of them travel through the portal system and regulate the activities of the ant. pit. * Five are releasing hormones that stimulate the ant. pit to secrete its hormones * gonadotropin releasing hormone * thyrotropin releasing hormone * corticotropin releasing hormone * prolactin releasing hormone * growth hormone releasing hormone * two are inhibiting hormones that suppress pituitary secretion * prolactin inhibiting hormone * somatostatin * Most of these hypothalamic hormones control the release of just one ant. pit. hormone * Accept gonadotropin-releasing hormone which controls the release of both FSH and LH * The other two hypothalamic hormones are secreted by way of the posterior pituitary * Oxytocin- made by the neurons in the paraventricular nuclei of the thalamus * antidiuretic hormone (vasopressin)- produced mainly by the supraoptic nuclei 5 Types of Anterior Pituitary Cells * Hormones secreted by cells that influence another endocrine gland are called tropic hormones or tropins * Thyrothrophs- secrete TSH that controls the thyroid gland * Gonadotrophs-secrete LH and FSH that controls the ovary and testes * Corticotrophs-secrete ACTH that controls the adrenal gland function Non-tropic * Lactotrophs- secretes prolactin ( PRL ) that controls milk production in the breast * Somatotrophs- secreted growth hormone ( GH ) that stimulates several tissues to secrete insulin-like growth factors, hormones that stimulate general body growth * The hormonal relationship between the hypothalamus, pituitary, and a more remote endocrine gland is called an axis. * There are 3 axis * hypothalamic-pituitary-gonaldal axis * hypothalamic-pituitary-thyroidal axis * hypothalamic-pituitary-adrenal axis Actions of Pituitary Hormones Anterior Pituitary * FSH- (produced by gonadotropes ) stimulates the ovary to develop eggs and sperm production in males Endocrine System * LH- (produced by gonadotropes ) stimulates ovulation and the corpus luteum to secrete estrogen and progesterone * stimulates interstitial cells of the testes to secrete testosterone * TSH- (produced by thyrotropes ) stimulates growth of the thyroid gland and the secretion of thyroid hormone * ACTH- (produced by corticotropes ) stimulates the adrenal cortex to secrete its hormones (corticosterioids), especially cortisol, which regulates glucose, fat, and protein metabolism. It also plays a central role in stress. Actions of Pituitary Hormones (cont) Anterior pituitary (cont) * Prolactin- secreted by lactotropes , which increase greatly in size and number during pregnancy * has no effects until after birth * stimulates the mammary glands to synthesize milk * In males, it makes the testes more sensitive to LH, thus, it indirectly enhances the...
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This note was uploaded on 01/30/2012 for the course BSC BSC1085 taught by Professor Sharonsimpson during the Fall '10 term at Broward College.
- Fall '10