Sympathetic nervous system vs Parasympathetic nervous system
How to tell Sympathetic nervous system and Parasympathetic nervous system apart when a board question makes them look alike.
Sympathetic is thoracolumbar short-pre/long-post; parasympathetic is craniosacral long-pre/short-post.
Side by side
Sympathetic outflow is thoracolumbar, uses short preganglionic and long postganglionic fibers, and supports fight-or-flight physiology.
Parasympathetic outflow is craniosacral, uses long preganglionic and short postganglionic fibers, and supports rest-and-digest physiology.
Sympathetic outflow is thoracolumbar, uses short preganglionic and long postganglionic fibers, and supports fight-or-flight physiology.
Parasympathetic outflow is craniosacral, uses long preganglionic and short postganglionic fibers, and supports rest-and-digest physiology.
Thoracolumbar T1-L2; short preganglionic, long postganglionic fibers; norepinephrine at most targets.
Craniosacral (CN III, VII, IX, X and S2-S4); long preganglionic, short postganglionic fibers; acetylcholine at targets.
The repair move
Before naming the answer, force the stem through the separator: Sympathetic is thoracolumbar short-pre/long-post; parasympathetic is craniosacral long-pre/short-post.
Try a free question
CoreAn autonomic outflow originates from spinal cord segments T1 to L2, has SHORT preganglionic fibers synapsing in paravertebral or prevertebral ganglia, and LONG postganglionic fibers releasing norepinephrine at target tissues. Which division of the autonomic nervous system is this?
Show answer and explanation
Answer: A. Sympathetic. Sympathetic nervous system: thoracolumbar (T1-L2) preganglionic neurons. SHORT preganglionic axons release ACh at nicotinic receptors on postganglionic neurons in paravertebral chain or prevertebral ganglia. LONG postganglionic axons release NOREPINEPHRINE at target organs (binding alpha and beta adrenergic receptors). EXCEPTION: sympathetic to adrenal medulla preganglionic releases ACh to chromaffin cells (which then release epinephrine into blood); sympathetic to sweat glands postganglionic releases ACh at muscarinic receptors. Drives 'fight-or-flight'.
Why the other choices are tempting
- B. Parasympathetic is craniosacral with LONG preganglionic and SHORT postganglionic fibers releasing ACh.
- C. Somatic nervous system has no ganglia and releases ACh at neuromuscular junctions (nicotinic Nm).
- D. Enteric nervous system is the intrinsic gut nervous system (modulated by autonomic input).
- E. Sensory afferents are not motor outputs.
Flashcards
Tap a card to flip it.
What clue supports Sympathetic nervous system?
Choose Sympathetic nervous system when the stem gives this pattern: Sympathetic outflow is thoracolumbar, uses short preganglionic and long postganglionic fibers, and supports fight-or-flight physiology.
What clue supports Parasympathetic nervous system?
Choose Parasympathetic nervous system when the stem gives this contrasting pattern: Parasympathetic outflow is craniosacral, uses long preganglionic and short postganglionic fibers, and supports rest-and-digest physiology.
Quick answers
What is the fastest way to tell Sympathetic nervous system from Parasympathetic nervous system?
Sympathetic is thoracolumbar short-pre/long-post; parasympathetic is craniosacral long-pre/short-post.
What is the key clue for Sympathetic nervous system?
Sympathetic outflow is thoracolumbar, uses short preganglionic and long postganglionic fibers, and supports fight-or-flight physiology.
What is the key clue for Parasympathetic nervous system?
Parasympathetic outflow is craniosacral, uses long preganglionic and short postganglionic fibers, and supports rest-and-digest physiology.