A precursor of adrenaline in the medulla of the suprarenal 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.
Referred to as norepinephrine, this hormone is released by specific nerve endings, primarily those associated with the sympathetic nervous system, as well as by the central region (medulla) of the adrenal glands.
The main role of noradrenaline is to contribute to the regulation of consistent blood pressure. It achieves this by triggering specific blood vessels to narrow (constrict) in situations where blood pressure decreases. Consequently, it is occasionally given via injection during emergency situations involving shock or significant bleeding.