10 - Hypothalamo-neurohypophysial system. Neurosecretion. Hormones of the posterior pituitary (neurohypophysis). Physiological effects and control of secretion

sections

• hypothalamo-neurohypophysial system

• neurosecretion

• hromones of posteriro pituitary

• insufficient secretion of vasopressin underlies…

• hypothalamo-neurohypophysial system

• The Hypothalamus is above the pituitary.

• Pituitary -divided into anterior and posterior.

• The anterior - primary hormone producing aspect, and is under neuroendocrine control

• Posterior stores only Oxytocin and Vasopressin and is under direct neural control

• The Hypothalamo-neurohypophysial system has the supraoptic -ADH and paraventricular- oxytocin nuclei and their axons which extend to the neurohypophysis in the posterior lobe of the pituitary gland.

• The posterior pituitary gland is not an endocrine gland because it does not make hormones.

• Instead, it stores and, later, releases hormones

• The posterior pituitary gland contains axon terminals of secretory neurons located in the hypothalamus called neurosecretory cells.

• neurosecretion

Neurosecretion: the storage, synthesis and release of hormones from neurons.

• Neurohormones are produced by neurosecretory cells and normally secreted from nerve cells in the brain → circulate into the blood.

• These neurohormones regulate endocrine and non-endocrine cells.

• Neurosecretory cells secrete their hormones further than normal into the extracellular space some distance from the target cell.

• hromones of posteriro pituitary

• The axons store the hormones which include- vasopressin, oxytocin.

• Secreted into the neurohypophysisal capillaries → they enter systemic circulation.

• as vasopressin in the arteries it also raises blood pressure via V1 receptor by contracting arteries. Control of secretion= negative feedback

• Oxytocin is used for regulation of childbirth and lactation for women, and sperm motility and testosterone levels for men. Control of secretion = positive feedback

• Source: supraoptic and paraventricular nuclei.

• Pain, hypoglycaemia

• Adh= alcohol decrease secretion, adh triggered by hyperosmorality

• insufficient secretion of vasopressin underlies…

diabetes insipidus a condition in which the body loses the capacity to concentrate urine. Affected individuals excrete as much as 20 liters of dilute urine per day. Over secretion of vasopressin causes the syndrome of inappropriate antidiuretic hormone.