Preganglionic sympathetic neurons are in the middle levels of the spinal cord, and usually send short axons in nerves from the spinal cord to synapse in nearby ganglia. Postganglionic sympathetic neurons then usually send long axons in nerves to reach their target cells. Sympathetic activation usually causes body responses appropriate for “fight or flight” activities, including diverting blood flow from the intestine to skeletal muscle (smooth muscle cells of blood vessels), increasing output of blood from the heart (cardiac muscle cells of the heart), and sweating (sweat gland cells). All of these changes increase the ability to convert stored energy into movement to deal with threatening situations.

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Level 3 Unit 2 Part 37: Parasympathetic nervous system