Sympathetic nervous system
What is the main function of the sympathetic nervous system?
Fight or flight response
Main function of parasympathetic nervous system?
rest and digest
What is another name for metasympathetic system?
Enteric nervous system
What is adrenal medulla function?
Releases stress hormones
Which division of ANS is responsible for “fight or flight”?
Sympathetic nervous system
What is the main neurotransmitter of postganglionic sympathetic neurons?
Norepinephrine (NE)
Origin of parasympathetic system?
Craniosacral (CN III, VII, IX, X, S2–S4)
Two plexuses of enteric system?
Myenteric and submucosal
What hormones does it release?
Epinephrine and norepinephrine
Where are parasympathetic ganglia located?
Near or within target organs
Which sympathetic fibers use acetylcholine instead of norepinephrine?
Sweat gland fibers
Fiber length pattern in parasympathetic system?
Long preganglionic, short postganglionic
Myenteric plexus function?
Controls GI motility
Why is adrenal medulla called modified ganglion?
It directly releases hormones instead of using postganglionic neurons
What does adrenal medulla release into blood?
A: Epinephrine (~80%) and norepinephrine (~20%)
What are adrenergic receptors of sympathetic system?
α1, α2, β1, β2, β3
Parasympathetic blockers
Which neurotransmitter relaxes smooth muscle in ENS?
Nitric oxide (NO)
What receptor type is on chromaffin cells?
Nicotinic receptors
Why is the adrenal medulla considered both neural and endocrine in function?
It is activated by sympathetic preganglionic neurons (neural input) but releases hormones (epinephrine/NE) into blood (endocrine output).
What is the effect of α1 receptor activation?
Vasoconstriction and pupil dilation
Why is vagus nerve (CN X) considered the most important parasympathetic nerve?
Because it provides parasympathetic innervation to most thoracic and abdominal organs.
What happens if ENS is damaged?
Severe motility disorders (e.g., ileus, Hirschsprung disease)
Explain full adrenal medulla pathway.
Preganglionic ACh → nicotinic receptor on chromaffin cells → release of Epi/NE into blood
BONUS)))))
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