Category: signaling
Two-arm coordination of involuntary visceral function. Sympathetic: thoracolumbar pre-ganglionic neurons → ganglion → post-ganglionic norepinephrine → α1 (vasoconstriction), α2 (presynaptic inhibition + CNS sedation), β1 (heart rate + contractility), β2 (bronchodilation + vasodilation), β3 (lipolysis). Adrenal medulla = modified sympathetic ganglion releasing epinephrine systemically. Parasympathetic: craniosacral pre-ganglionic → ganglion (close to target organ) → post-ganglionic acetylcholine → M2 (heart — bradycardia), M3 (smooth muscle contraction + glandular secretion). Pharmacology: α1-blockers (prazosin, tamsulosin) — BPH + HTN; α2-agonists (clonidine, dexmedetomidine) — central sympathetic suppression + sedation; β1-blockers (metoprolol, atenolol) — CV; β2-agonists (albuterol) — asthma; antimuscarinics (atropine, oxybutynin, glycopyrrolate) — OAB, bradycardia rescue, secretion drying.