Also known as norepinephrine, a hormone secreted by certain nerve endings (principally those of the sympathetic nervous system) and by the medulla (centre) of the adrenal glands. Noradrenaline’s primary function is to help maintain a constant blood pressure by way of stimulating certain blood vessels to constrict (narrow) when the blood pressure falls. For this reason, it may sometimes be injected in the emergency treatment of shock or severe bleeding. (See also adrenaline.)
A precursor of ADRENALINE in the medulla of the suprarenal glands (see ADRENAL GLANDS). It is also present in the BRAIN. Its main function is to mediate the transmission of impulses in the SYMPATHETIC NERVOUS SYSTEM; it also has a transmitter function in the brain.
(norepinephrine) n. a hormone, closely related to *adrenaline and with similar actions, secreted by the medulla of the *adrenal gland and also released as a *neurotransmitter by sympathetic nerve endings. Among its many actions are constriction of small blood vessels leading to an increase in blood pressure, increased blood flow through the coronary arteries and a slowing of the heart rate, increase in the rate and depth of breathing, and relaxation of the smooth muscle in intestinal walls.
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