Autonomic Nervous System

I. Divisions
A. Sympathetic
fight or flight response
B. Parasympathetic
rest and digestion
II. Involuntary Motor System
A. Autonomic vs. Somatic motor systems
1. Somatic
voluntary
direct synapse
excitatory

2. Autonomic
involuntary
disynaptic (preganglion, postganglion)
Excitatory and inhibitory
III General nerve pathways
A. Sympathetic
Preganglion cell body – gray matter
axons move through ventral root of spinal nerve
synapse w/ postganglion at sympathetic chain ganglion

axons of postganglions exit via
Spinal nerve
Sympathetic nerve
Exceptions: some pre do not synapse at symp chain
Splanchnic nerve
axons of preganglion exit Splanchnic nerve and
synapse at collateral ganglion w/post
Adrenal gland
preganglion synapses directly w/adrenal

B. Parasympathetic
cell bodies of preganglion – brainstem (nuclei)
and sacral region of spinal cord
axons move through cranial nerves
and through spinal nerves
synapse w/ postganglion at ganglia near or in the target
IV. Signal transmission
A. Sympathetic
Preganglion secretes Acetylcholine (Cholinergic)
Postganglion – receptor = Nicotinic
Postganglion secretes Norepinephrine (Adrenergic)

Target (smooth muscle, cardiac, glands)
Receptor = Adrenergic (α,β)
Sweat Glands Preganglion secretes Acetylcholine
Postganglion – nicotinic receptor
Postganglion secretes Acetylcholine
Sweat gland – muscarinic receptor

B. Parasympathetic
Preganglion secretes Acetylcholine (Cholinergic)
Postganglion – receptor = nicotinic
Postganglion secretes Acetylcholine
Target (Smooth muscle, heart, glands)
receptor = muscarinic
V. ANS generalized
A. Regulated

B. Excitatory and inhibitory
depends on the target organ
C. Opposite effects
VI. Autonomic control
A. Cardiovascular function
Sympathetic: Norepinephrine -
Increases cardiac muscle contractions
Increases blood pressure
Parasympathetic: Acetylcholine
Decrease in cardiac output due to decrease in
calcium influx