Sympathetic Nervous System

The sympathetic nervous system is the division of the autonomic nervous system that triggers the "fight or flight" response, preparing the body for action or stress. Sympathetic activation increases heart rate and blood pressure, dilates airways and pupils, and inhibits digestion - all to mobilize energy and resources in a crisis or energetic activity.

• Sympathetic nerves originate from the thoracic and lumbar regions of the spinal cord (thoracolumbar origin). When activated, they release norepinephrine (and prompt the adrenal medulla to release epinephrine) at target organs, which causes effects like faster heartbeat, glucose release from the liver, and sweating.
• Key sympathetic pathway: the adrenal medulla is essentially a specialized sympathetic organ that, when stimulated, secretes adrenaline (epinephrine) into the bloodstream. This hormone boosts and prolongs the fight-or-flight response body-wide (e.g., increasing alertness and fuel availability).
• Sympathetic ganglia are typically arranged in chains (sympathetic trunks) alongside the spinal column. This arrangement allows a coordinated, whole-body response. For instance, a sudden fright can simultaneously dilate pupils, increase heart rate, and release glucose - multiple organs responding together under sympathetic control.

• If a question describes a scenario like being startled or exercising - with signs such as rapid pulse, pale skin (blood diverted to muscles), and dilated pupils -> that's the sympathetic nervous system at work (fight-or-flight).
• If asked which autonomic division uses norepinephrine on target organs and prepares the body for emergencies -> the sympathetic nervous system. Clue words: "adrenergic" activity, adrenaline, or increased heart rate all point to sympathetic effects.
• Be ready for comparisons: e.g., a question might give a list of effects and ask which are sympathetic vs parasympathetic. Remember that sympathetic effects include things like inhibited digestion and accelerated breathing/heart rate, whereas parasympathetic do the opposite.