This gland is situated on the kidney. Each kidney has an adrenal gland placed on it. Internally, the adrenal gland is divisible into an outer Cortex and an inner medulla. The outer cortex secretes three different hormones:
(a) Mineralocorticoid:
This hormone helps in the re-absorption of minerals in the nephron.
(b) Glucocorticoid:
This hormone helps in the re-absorption of glucose in the nephron.
(c) Androgen:
Its action is similar to that of testosterone, but it is not as powerful as testosterone. The inner part of adrenal gland, know as medulla, secretes only one hormone. This hormone is called adrenaline or epinephrine. The actions of adrenaline on different tissues and systems are different. Adrenaline increases heartbeat rate, constricts all blood vessels except those that supply blood to heart muscles and skeletal muscles. Adrenaline increases blood pressure and the rate of respiration. Breakdown of glycogen into glucose is accelerated. Smooth muscles of the skin contract and the volume of urine are reduced. Adrenaline produces a sense of restlessness, anxiety and fatigue. Excitement generally stimulates adrenaline secretion.
ADVERTISEMENTS:
Adrenaline is released into the blood in times of stress, emotional disturbance, and threatened dangers. Adrenaline helps the subject cope with the situation. When two animals or persons are looked in a fight, there is a surge of adrenaline in their blood. Adrenaline is called fight and flight hormone because it is present in the blood of both the winner and the loser. The word ‘fight’ represents the winner and ‘flight’ represents the loser.
Tumor in the adrenal gland may lead to excess secretion of hormones form the adrenal cortex. This may cause deposition of fat in the neck, face and back. In males, there may be excessive hair growth. Females may develop beard and moustache. Males may become impotent because of the atrophy of the testis and females may become sterile. All these symptoms are the characteristics of cushing’s syndrome (named after an American surgeon, Harvey William Cushing). Loss of adrenal gland leads to Addison’s disease (named after a British surgeon, Thomas Addison). A person suffering from this disease has low blood pressure, great muscular weakness, and pigmented skin (copper-coloured).