The head of a Roman snail, four tentacles well visible. [RN] Observing a snail crawling around, the view is immediately attracted by its head, orienting itself in its surroundings using the tentacles. The snail feels its environment, touches an obstacle and withdraws the tentacle.
Norepinephrine is a neurotransmitter secreted by neurons in the sympathetic nervous system. This chemical is secreted in response to stress, which triggers the 'fight or flight response.' The release of norepinephrine causes several changes that help our body to work more efficiently.
norepinephrine (NE). [norâ²nÃ´râ²epinef]. rin an adrenergic (hormone) catecholamine that acts to increase blood pressure by vasoconstriction but does not affect cardiac. Output it is synthesized by the adrenal, medulla the peripheral sympathetic, nerves and the central nervous. system