Sympatikus

Sympatikus, or the sympathetic nervous system, is part of the autonomic nervous system responsible for rapid involuntary responses during stress. It is classically described as the thoracolumbar division, with neurons located in the intermediolateral columns of the spinal cord from T1 to L2 and preganglionic fibers that synapse in paravertebral (sympathetic chain) or prevertebral ganglia near major arteries.

Postganglionic neurons usually release norepinephrine, while preganglionic fibers release acetylcholine. The adrenal medulla acts as a modified ganglion, releasing epinephrine and norepinephrine into the bloodstream. The system communicates via adrenergic receptors, including alpha and beta subtypes.

Activation supports the fight-or-flight response: heart rate and contractility increase; airways dilate; pupils dilate; metabolic effects raise glucose and fatty acids; blood flow is shifted toward skeletal muscles and away from the gut and skin; sweating and piloerection may occur.

Regulation and clinical relevance: The sympathetic system is controlled by higher brain centers such as the hypothalamus and brainstem, and it interacts with the parasympathetic system to maintain homeostasis. Abnormal sympathetic activity is seen in hypertension, heart failure, anxiety disorders, and pheochromocytoma. Therapies include adrenergic agonists and antagonists (for example, beta blockers and alpha blockers).