Norepinephrine is stored in vesicles in the terminal of a neuron.
Normally norepinephrine (also called noradrenaline) is released in small
quantities from the vesicles into the synaptic space. Then it binds to
adrenergic receptors on the receiving cell, and depending on what type
of receiving cell is present, e.g., a neuron or a cardiac cell, a
specific response is produced. Neurons might fire, or a cardiac cell
might fire to increase the heart rate.