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Human Body
Noradrenaline is the precursor of adrenaline.
Fear, pain, exposure to cold, low blood-pressure, emotional upsets and other challenging experiences stimulate the release of these hormones.
They are secreted in response from sympathetic nerves. Their effects are basically similar, but there are some key differences. Norepinephrine which is also a neuro-transmitter is also released by the ends of the sympathetic nervefibres.
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The secretion of these two hormones is controlled by the sympathetic nervous system and the higher centres in the cerebral cortex and hypothalamus. Thus the functioning of the adrenal medulla is intimately linked with the sympathetic nervous system. Both the release and resynthesis of the hormones are triggered by nerve impulses. The amount of adrenaline, in circulation in general, is about 1 part to 20 millions, while a hundred thousand times more is stored in the glands as reserve.
Adrenaline has been called the emergency hormone. Its entry into the blood causes a tremendous heightening of vigour and tensing of the nervous system. More sugar is sent into the blood from the liver and more red blood-cells are forced into circulation from the blood reservoirs of the liver and spleen. The heart beats more strongly, the bloodpressure and temperature rises, breathing is more rapid, and the blood rushes in the brain as well as to the skeletal muscles of the limbs. On the other hand, the digestion. and everything non-essential is inhibited, arrested and suppressed. All this is in preparation of 'fight or flight' in response to the emergency.
Through repeated excitement, anger, fear etc. the adrenal glands may be exhausted of their reserve supply of adrenaline secretion. If enough time is not allowed for the glands to recuperate, amount of the secretion will be insufficient to meet the demand. The result would be temporary or chronic adrenal deficiency. It is characterized by indecision, a tendency to worry and an inclination to weep for the slightest provocation
(vii) The Gonads (Sex-glands)
The term "gonad" literally means "seed", and the male
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