The fight-or-flight response is mediated by which nervous system division?

• A. Parasympathetic Nervous System
• B. Sympathetic Nervous System
• C. Cerebrum
• D. Brainstem

Answer: (B)

Fight-or-flight is mediated by the sympathetic division of the autonomic nervous system. When activated, it readies the body for action by increasing heart rate and contractility, widening airways, dilating pupils, and redirecting blood to muscles, while slowing digestion. The sympathetic pathway starts in the thoracic and upper lumbar spinal cord, with preganglionic neurons synapsing in sympathetic ganglia and postganglionic neurons releasing norepinephrine at target organs; the adrenal medulla can also release adrenaline to amplify the response. The parasympathetic division promotes resting and digesting, opposite to this surge. Brain regions like the cerebrum or brainstem influence the response but do not constitute the division that mediates fight-or-flight itself.