Primary endocrine organs 1. Hypothalamus and Pituitary gland- regulate the entire body. Hypothalamus- primary endocrine gland. It secretes hormones that affect the pituitary glands. When a neuron in the hypo releases the tropic hormone it is called a nuerohormone. All hormones are peptides. Pituitary gland is connected to the hypothalamus. It is divided into the anterior lobe (epithelial tissue) and the posterior lobe(neural tissue) 2. Neural connection between the hypo and the post. Pituitary gland. The posterior lobe has axon terminals that originate in the hypo. And secrete ADH(vasopressin) and Oxytocin. ADH is synthesized in the paraventricular nucleus in the hypo and oxy is synthesized in the supraoptic nucleus In the HYPO. They are packaged into secretory vesicles and are released by exocytosis when signaled from another neuron from the axon terminals. (neuroendocrine reflex) ADH is stimulated by increase in plasma solute and targets the kidney. It increases water reabsorption. Oxy is stimulated by pressure in the uterus, pregnancy. Targets the uterus and increases contractions and milk leakage. 3. Blood Connection Between the hypothalamus and the anterior pituitary gland. Anterior lobe and hypo controls trophic hormone (regulate secretion of other hormones). Trophic hormones can inhibit or stimulate secretion. Pathway- hypo releases trophic hormone which releases another trophic hormone from the anterior pit. Which commands the release of 3 rd hormone from another endocrine gland and it effects target cells throughout the body. 4. Anatomy of hypothalamic Pituitary Portal System Portal system - made up of a series of 2 capillary beds. Neurons in the hypothalamus secrete tropic hormones into the capillary bed in the medina eminence of the hypo. These nuerohormones travel to the pituitary to a 2 nd capillary bed via a portal vein. The trophic hormones stimulate or inhibit the release of hormones from the anterior pit. The portal system allows for the hypothalamus to directly deliver its trophic hormones to the ant. Pituitary rather than being returned to the heart and sent to the gland. 5. Trophic Hormones of the hypothalamus and Anterior Pituitary PRH stimulates pituitary to release prolactin, stimulates mamory gland develop. And milk secretion.
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- Fall '08
- Endocrine System