The branch of the autonomic nervous system that plays the major role in an activated state or stress response, and associated with, for example, increased heart rate, dilated pupils, higher blood pressure, and inhibited digestive processes.
See Autonomic nervous system (ANS), Catecholamines, Central nervous system (CNS), Cholinergic neurotransmitter system, Epinephrine (or adrenaline), Nerve Growth Factor (NGF), Neural crest, Neuroticism, Norephinephrine (or noradrenaline), Parasympathetic nervous system (PNS), Peripheral nervous system