What is the nature of the relationship between the hypothalamus and each lobe of the pituitary gland? What are the hormones released by the posterior pituitary; what organs do these hormones target?
Of the endocrine tissues that function only to secrete hormones, the hypothalamus portion of the brain and the pituitary gland together regulate the greatest number of the body's life functions. The hypothalamus secretes releasing hormones which act to stimulate or inhibit the anterior lobe of the pituitary gland to release or stop the flow of its hormones. Connected to the hypothalamus by a stalk, the posterior pituitary serves as a storage area for two hormones which are actually secreted by the hypothalamus. The hormones flow from the hypothalamus to the posterior pituitary along nerves in the posterior pituitary's connecting stalk. Neural impulses from the hypothalamus cause the posterior pituitary to release the hormones. Oxytocin stimulates contraction of the uterine wall and the release of milk into the mammary glands. Vasopressin stimulates constriction of blood vessels and smooth muscle as well as stimulating increased water reabsorbtion by the kidneys.
