NETTER - Neuroscience Flash Cards

Posterior Pituitary (Neurohypophysial)
Hormones: Oxytocin and Vasopressin
1. Forebrain pathways to supraoptic and paraventricular nuclei
2. Brain stem pathways to supraoptic and paraventricular nuclei
3. Paraventricular nucleus (PVN)
4. Supraoptic nucleus (SON)
5. Posterior lobe of the pituitary gland
6. Venous drainage of the posterior lobe
7. Anterior lobe of the pituitary gland
8. Neurohypophysial tract
9. Blood-borne signals reaching PVN and SON
Comment: The magnocellular neurons of the SON and PVN
synthesize and secrete both oxytocin and arginine-vasopressin
(antidiuretic hormone [ADH]), along with their neurophysin carrier
proteins. These neurons send axons (supraopticohypophysial tract)
into the posterior pituitary, where they terminate on fenestrated
capillaries and secrete their hormones directly into the general
circulation. Oxytocin neurons respond to estrogen and to afferent
neuronal signals from suckling; oxytocin stimulates milk let-down and
uterine contraction in pregnancy. Vasopressin neurons respond to
changes in blood osmolarity, secreting vasopressin in the presence
of high osmolarity; vasopressin causes the collecting tubules of the
kidney to increase water resorption and prevents diuresis. Damage
to the supraopticohypophysial tract (from pituitary stalk section)
results in diabetes insipidus, with a loss of vasopressin secretion
and production of large quantities of dilute urine, accompanied
by polydipsia. Excessive vasopressin secretion (called syndrome
of inappropriate secretion of ADH [SIADH]) may occur because of
partial damage to the hypothalamus, a vasopressin-secreting tumor
in the periphery, or pharmacologic agents. SIADH results in hypoosmolar
serum, hyponatremia, and high urine osmolarity.
Systemic Neuroscience See book 16.17