Sympathikus

The Sympathikus, or sympathetic nervous system, is one of the two main divisions of the autonomic nervous system. It prepares the body for rapid responses to perceived threats or stress, coordinating cardiovascular, respiratory, metabolic, and other systemic adjustments. Anatomically, its neurons primarily arise from the thoracolumbar region of the spinal cord (preganglionic neurons from T1 to L2) and connect through the paravertebral sympathetic chain and prevertebral (collateral) ganglia to reach target organs.

The efferent pathways follow a consistent chemical scheme. Preganglionic neurons release acetylcholine onto nicotinic receptors on postganglionic neurons. Most postganglionic fibers then release norepinephrine onto adrenergic receptors in target tissues. An important exception are the sympathetic fibers that innervate sweat glands and some cutaneous vessels, which use acetylcholine acting on muscarinic receptors. The adrenal medulla is a modified sympathetic ganglion; preganglionic fibers stimulate chromaffin cells to release epinephrine and norepinephrine into the bloodstream, amplifying and prolonging the response.

Physiological effects of sympathetic activation include increased heart rate and contractility, bronchodilation, pupil dilation, and redirecting blood flow from the gastrointestinal tract to skeletal muscles. It promotes energy mobilization by releasing glucose and fatty acids, reduces nonessential activities, and enhances alertness and metabolic readiness. The system operates in concert with the parasympathetic division, balancing homeostasis across varying conditions.

Clinically, sympathetic overactivity is linked to hypertension, anxiety disorders, and pheochromocytoma. Pharmacologic modulation includes adrenergic receptor blockers (alpha- and beta-blockers) and agents that reduce central sympathetic outflow.