There are two adrenal glands one on the top of each kidney. Internally the adrenal gland is divisible into an outer cortex and inner medulla.
The adrenal cortex secretes many hormones, commonly called corticoids.
(a) Mineralcorticoids: It acts on kidney and promotes absorption of Na and water into blood and excretion of
(b) Glucocorticoids: These affect carbohydrate metabolism. It stimulates the liver to synthesize carbohydrates from non-carbohydrates such as amino acids and proteins.
This disease in caused by the deficiency of mineralocorticoids and glucocorticoids. Its symptoms include low blood sugar, low plasma Na*, high plasma K, bronze like pigmentation of skin.
It is caused by excess of glucocorticoids. It is characterised by high blood sugar, rise in plasma Na*. Fall in plasma K', high blood pressure, obesity etc.
Small amounts of androgenic steroids are also secreted by the adrenal cortex which play a role in the growth of axial hair, pubic hair and facial hair during puberty.
The medulla of the adrenal glands secrets two hormones:
(1) Norepinephrine or noradrenaline
(2) Epinephrine or adrenaline.
These hormones are secreted at the time of stress, emotional disturbance or when the individual is threatened by a dangerous situation. Adrenaline increase heart beat, constrict all blood vessels except those that supply blood to heart muscles and skeletal muscles. It also increases blood pressure and the rate of respiration. Thus changes caused by this hormones prepare the body to react during an emergency. Thus it is also called the emergency hormone.
Adrenaline can also be called fight, fright and flight hormone because there is surge of adrenaline when a person is fighting, is frightened or is running fast.