Anatomy (ANS - 11/3) Flashcards
ANS (Visceral motor system) innervates __________
Smooth muscle, cardiac muscle, glands
How many neurons in ANS system
2 (preganglionic cell body in CNS and postganglionic cell body in peripheral ganglion - motor)
Preganglionic cell bodies
CNS - multipolar
Sympathetic in Lateral Horn (T1-L2/3)
Parasympathetic in Brain stem (CN III, VII, IX, X) or sacral region S2-S4
Postganglionic cell bodies
Autonomic ganglion (depending on para/sympathetic) - multipolar
Sympathetic originates from preganglionic cell neurons having cell bodies in _____
Lateral gray horn (intermediolateral cell column) of spinal cord levels T1 to L2/3
Parasympathetic have cell bodies in ____
Cranial nerve nuclei III, VII, IX, X and spinal cord segments
S2,3,4
Where do preganglionic sympathetic neurons exit from lateral horn?
Ventral root (motor) to join spinal nerve
Sympathetic preganglionic neuron pathway
Lateral horn –> ventral root –> spinal cord –> communicating white ramus –> sympathetic chain to synapse with postganglionic OR travel to prevertebral ganglion
Lateral Horn
T1-L2/3
Sympathetic preganglionic cell bodies
Intermediolateral cell column
White communicating ramus
Spinal nerve to sympathetic chain ganglia (preganglionic sympathetic fibers - axons)
Myelinated axons
14 pairs (28 total) from T1-L2
Also contain visceral sensory nerves
4 Options for Preganglionic Sympathetic neurons
- Terminate with postsynaptic neuron of paravertebral ganglion at that spinal cord level
- Ascend to terminated at higher paravertebral level
- Descend to terminate at lower paravertebral leve
- Traverse sympathetic trunk w/o terminating –> splanchnic (visceral) nerves –> prevertebral ganglia (pre-aortic) or adrenal gland
Postganglionic sympathetic cell bodies
Paravertebral (sympathetic chain) ganglia OR prevertebral (preaortic) ganglia
Cells of adrenal medulla homologous to postganglionic neurons
Cervical paravertebral ganglia
3 ganglia (per side) --> 8 cervical spinal nerves Superior cervical ganglion (largest) --> supply head also, Middle, Inferior
How do postganglionic axons leave paravertebral ganglia?
Gray rami communicans
How many pairs of gray rami?
31 pairs - communicate with 31 pairs of spinal nerves (cervical, thoracic, lumbar, sacral and coccygeal)
Gray rami communicans
31 pairs
Unmyelinated axons from postganglionic sympathetic axons –> spinal nerves
Cardiopulmonary sympathetic nerves
From paravertebral ganglia to supply postG sym fibers to heart and lungs (cardiac, pulmonary, aortic plexuses)
From middle/inferior cervical paravertebral panglia or in upper 5 thoracic paravertebral ganglia
Cephalic arterial rami (Sym)
postS sym fibers to head, travel with blood vessels, from superior cervical ganglion
Prevertebral/preaortic ganglia
3 main ones - celiac ganglion, superior mesenteric ganglion, inferior mesenteric ganglion
Also a renal ganglion closely associated with superior mesenteric ganglion
Receive preganglionic sympathetic input over splanchnic nerves (visceral)
Splanchnic nerves
Carry preganglionic fibers from sypmathetic chain to prevertebral ganglia - postganglionic neruons in prevertebral G send axons to organ of innervation
What nerves supply prevertebral ganglia with preganglionic neurons?
Splanchnic nerves
Adrenal gland (suprarenal gland(
Equivalent to postganglionic neuron
Release primarily epinephrine into vascular system
Preganglionic neurons pass through paravertebral and prevertebral ganglia to synapse at AM.
What does preganglionic Sym neuron release - onto what receptor
Acetylcholine onto nicotinic receptor of PostG sym neuron RO adrenal medulla
What does PostG sym neuron release? What do receptors do?
Norepinephrine onto
a1, b1 - excitatory
a2, b2 - inhibitory
Location of PreG parasympathetic cell bodies
Brain stem (for cranial nerves III, VII, IX, X) and sacral spinal cord S2-S4 (for spinal nerves)
LONG - to postG near organ of innervation
Postganglionic parasympathetic cell bodies
Closer to organ of innervation
In ganglia
In head - named, distinct
Vagus nerve/pelvic nears - terminal ganglia near organs
What do preG para neurons release? Receptors?
Acetylcholine to Nicotinic receptors on postG
What do postG para neurons release? Receptors?
Acetylcholine to Muscarinic receptors on organ
Enteric nervous system overview
Nerve cell bodies of myenteric and submucosal nerve plexus
Postganglionic Para neurons
Terminal ganglia
Where are postganglionic parasympathetic nerve cell bodies located?
Cranial nerve and terminal ganglia
Preganglionic Symp Neurons to the head have cell bodies in _________
spinal cord segments T1-T2
White Rami communicantes present in body
28 (14*2)
PostG symp neurons to the head have their cell bodies located in _________
paravertebral ganglia
Paravertebral ganglia receive innervation via
white rami
What nerves supply prevertebral ganglia with preganglionic neurons
splanchnic nerves
Gray rami communicantes
62 (31*2)
What is the location of postG sym nerve fibers suppling the head?
Superior cervical ganglion
Where are cell bodies of cardiopulmonary nerves (SYM)
Paravertebral plexus
Ways postganglionic axons leave paravertebral ganglia
Gray rami communicans –> spinal nerves
Cephalic arterial branches/periarterial sym plexus –> head region
Cardiopulmonary nerves –> heart, lungs, esophagus (cardiac/pulmonary/aortic plexuses)
Why are cardiopulmonary splanchnic nerves postganglionic white abdominopelvic splanchnic nerves preG?
CPS come from sympathetic chain ganglia where they synapsed, whereas APS do NOT synapse when they run through SCG and synapse in the prevertebral ganglia
Adrenal medulla cells
Chromaffin - release primarily epinephrine
Exception to rule that postG sym release norepinephrine
PostG sym release acetylcholine to innervate sweat glands, smooth muscle in some arteries (i.e. skeletal muscle)
vagus nerve
CN X
Preganglionic neurons to postganglionic parasym neurons associated w/ heart, lungs, most of abdominal viscera
Largest source of preganglionic para nerve fibers
Pelvic splanchnic nerves
output of S2-S4 preganglionic to postG parasym –> distal 1/3 of large intestine, pelvic viscera, genitalia
