Outline the Relationship Between the Hypothalamus and the Pituitary Gland • The Hypothalamus acts as a connection between the nervous system and the endocrine system. • The Pituitary Gland has two parts: Anterior and Posterior • Posterior • Hypothalamus and Posterior Pituitary are connected by nuerosecretory cells. • Hormones secreted by the posterior pituitary are produced in the hypothalamus • Nerve impulses from the hypothalamus control the release of hormones (ADH, Oxytocin) from the posterior pituitary • Anterior • Neurosecretory cells in the hypothalamus produce hormones (releasing factors) which are released into the portal vein which travels to the anterior pituitary. • These releasing factors cause the release of one of six protein hormones. • These hormones released by the anterior pituitary are produced by the anterior lobe of the pituitary gland.
Explain the Control of ADH (vasopressin) Secretion by Negative Feedback • Negative Feedback Mechanism – used to create a homeostatic environment in the body. Adjusts abnormal conditions back to normal. • Process • The Hypothalamus contains osmosreceptors which detect the concentration of dissolved particles in the blood plasma. • When an increase is detected, an impulse is sent, and ADH is released into the posterior pituitary and then into the bloodstream. • ADH travels to the kidney, and makes the walls of the collecting duct more permeable to water, allowing reabsorption of water back into the blood. • If the concentration is low, then no ADH is released and less water is reabsorbed by the bloodstream from the Kidneys, producing dilute urine.