SYMPATHETIC DIVISIONPARASYMPATHETIC DIVISION DISTRIBUTION: From thoracic & lumbar nerve roots DISTRIBUTION: From cranial & sacral nerve roots STRUCTURE: Presynaptic neuron short, secretes AC Synapse in chain ganglion (or adrenal medulla) Postsynaptic neuron long, secretes NE (exception: short in adrenal medulla, secretes mostly epinephrine) STRUCTURE: Presynaptic neuron very long, secretes AC Synapse on or close to target organ (e.g., celiac ganglion) Postsynaptic neuron short, secretes AC “FIGHT OR FLIGHT” RESPONSE: Increased blood flow (except to viscera) Increased heart rate, breathing, sweating; contraction of arrector pili muscles Lowered stimulatory thresholds (quicker and more certain response, more alert) Inhibition of digestion & peristalsis Decreased prothrombin time (quicker clotting) “REST AND RUMINATE” RESPONSE: Decreased blood flow (but increased to viscera) Slower, more relaxed heart rate, breathing; arrector pili muscles inhibited Raised stimulatory thresholds (less likely to respond, response slower, less alert) Stimulates digestion, peristalsis, sexual activity Increased prothrombin time (slower clotting) Abbreviations: AC = Acetylcholine; NE = Norepinephrine AUTONOMIC NERVOUS SYSTEM