Chapter 17 - Section 17.2 - Study Guide - Assess Your Learning Outcomes - Page 669: 4

Two hormones synthesized in the hypothalamus and stored in the posterior pituitary are oxytocin and antidiuretic hormone (ADH), also known as vasopressin. These hormones are produced in the cell bodies of neurons located in the hypothalamus and are then transported to the posterior pituitary for storage and later release. The process involves neural pathways and specialized nerve fibers known as hypothalamo-hypophyseal tracts. Here's how oxytocin and ADH are transported to the pituitary and how their release into the bloodstream is controlled: 1. **Synthesis and Transport to the Posterior Pituitary:** - Oxytocin and ADH are synthesized in the cell bodies of specific neurons in the hypothalamus. - Once synthesized, these hormones travel down the hypothalamo-hypophyseal tracts, which are bundles of nerve fibers extending from the hypothalamus to the posterior pituitary. - These nerve fibers pass through the infundibulum (a stalk-like structure that connects the hypothalamus and the pituitary gland) and terminate in the posterior pituitary. - In the posterior pituitary, oxytocin and ADH are stored in vesicles within nerve terminals, ready for release when appropriate signals are received. 2. **Release into the Bloodstream:** - Oxytocin and ADH are released into the bloodstream in response to specific physiological stimuli and signals from the hypothalamus. - The hypothalamus monitors various conditions in the body and responds to triggers such as changes in blood volume, osmolarity (concentration of solutes), and stretch of certain tissues. - For example, ADH is released in response to increased blood osmolarity (indicating dehydration) or decreased blood volume (as in cases of low fluid intake or blood loss). ADH helps regulate water balance by promoting water reabsorption in the kidneys. - Oxytocin is released during labor contractions and breastfeeding in response to uterine stretch and stimulation of the nipples. It promotes uterine contractions during childbirth and stimulates milk ejection during breastfeeding. 3. **Control of Release:** - The release of oxytocin and ADH is controlled by neuroendocrine reflexes involving the hypothalamus. - Nerve impulses originating in response to specific physiological signals travel along the hypothalamo-hypophyseal tracts to the nerve terminals in the posterior pituitary. - These nerve impulses trigger the release of stored oxytocin or ADH into the bloodstream. - The release of these hormones is tightly regulated through feedback mechanisms. For example, when blood osmolarity or blood volume returns to normal levels, the release of ADH is suppressed. In summary, oxytocin and ADH are synthesized in the hypothalamus, transported to the posterior pituitary through neural pathways, and stored there for later release. The release of these hormones into the bloodstream is controlled by neural signals originating from the hypothalamus in response to specific physiological conditions and stimuli.

Two hormones synthesized in the hypothalamus and stored in the posterior pituitary are oxytocin and antidiuretic hormone (ADH), also known as vasopressin. These hormones are produced in the cell bodies of neurons located in the hypothalamus and are then transported to the posterior pituitary for storage and later release. The process involves neural pathways and specialized nerve fibers known as hypothalamo-hypophyseal tracts. Here's how oxytocin and ADH are transported to the pituitary and how their release into the bloodstream is controlled: 1. **Synthesis and Transport to the Posterior Pituitary:** - Oxytocin and ADH are synthesized in the cell bodies of specific neurons in the hypothalamus. - Once synthesized, these hormones travel down the hypothalamo-hypophyseal tracts, which are bundles of nerve fibers extending from the hypothalamus to the posterior pituitary. - These nerve fibers pass through the infundibulum (a stalk-like structure that connects the hypothalamus and the pituitary gland) and terminate in the posterior pituitary. - In the posterior pituitary, oxytocin and ADH are stored in vesicles within nerve terminals, ready for release when appropriate signals are received. 2. **Release into the Bloodstream:** - Oxytocin and ADH are released into the bloodstream in response to specific physiological stimuli and signals from the hypothalamus. - The hypothalamus monitors various conditions in the body and responds to triggers such as changes in blood volume, osmolarity (concentration of solutes), and stretch of certain tissues. - For example, ADH is released in response to increased blood osmolarity (indicating dehydration) or decreased blood volume (as in cases of low fluid intake or blood loss). ADH helps regulate water balance by promoting water reabsorption in the kidneys. - Oxytocin is released during labor contractions and breastfeeding in response to uterine stretch and stimulation of the nipples. It promotes uterine contractions during childbirth and stimulates milk ejection during breastfeeding. 3. **Control of Release:** - The release of oxytocin and ADH is controlled by neuroendocrine reflexes involving the hypothalamus. - Nerve impulses originating in response to specific physiological signals travel along the hypothalamo-hypophyseal tracts to the nerve terminals in the posterior pituitary. - These nerve impulses trigger the release of stored oxytocin or ADH into the bloodstream. - The release of these hormones is tightly regulated through feedback mechanisms. For example, when blood osmolarity or blood volume returns to normal levels, the release of ADH is suppressed. In summary, oxytocin and ADH are synthesized in the hypothalamus, transported to the posterior pituitary through neural pathways, and stored there for later release. The release of these hormones into the bloodstream is controlled by neural signals originating from the hypothalamus in response to specific physiological conditions and stimuli.