mammary glands. Vasopressin stimulates constriction of blood vessels and smooth muscle as well as stimulating increased water reabsorbtion by the kidneys. 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.
The two adrenals, which lie very near the surface of the kidneys, play multi-faceted roles effecting a wide variety of responses in the body. Each adrenal is actually made up of two glands that arise from different embryonic material and remain functionally separate: the inner adrenal medulla and the outer adrenal cortex.
The adrenal medulla releases adrenaline and noradrenaline which cause the "fight-or-flight" responses typified by a rise in blood pressure, an acceleration of heart beat, an increased conversion of glycogen to glucose and release of glucose into the blood by the liver, a vasoconstriction of blood vessels serving the skin and digestive tract, and a vasodilatation of blood vessels serving the skeletal and heart muscles. Adrenaline also acts as an inhibitor to insulin. Adrenaline elevates blood-sugar levels by stimulating liver cells to break down glycogen into glucose and by stimulating muscle cells to turn stored glycogen into lactic acid which, released into the blood by the muscle cells, is converted into glucose by the liver.
The adrenal cortex secretes three types of hormones all of which are steroidal.
