Principles of Anatomy: Autonomics

perception

conscious awareness of a stimulus

visceral nervous system

unconscious control/ awareness of stimuli/effectors

general somatic efferent

1. cell body of motor neuron lives in ventral horn

2. axon leaves VH to form ventral root

3. Innervates a muscle in the PNS

general visceral efferent

1. cell body lives in lateral horn of spinal cord

2. axon leaves cord via VH to form ventral root

3. Preganglionic neuron releases ACh in synapse

4. Cell body of postganglionic neuron lives in PNS

5. releases ACh and NE

6. Innervates smooth muscle, cardiac muscle, glands

lateral horn

• general visceral efferent pathway 

• grey matter

• only found in spinal segments T1-L2 and S2, S3, S4

• multipolar motor neuron lives here 

preganglionic fiber

• neuron #1

• cell body lives in lateral horn

• releases ACh into synapse w/ neuron #2

postganglionic fiber

• neuron #2

• Cell body lives in PNS

• releases ACh and NE

• innervates smooth muscle, cardiac muscle, glands

autonomic ganglion

cluster of cell bodies in PNS

• cell body of post ganglionic neuron 

Parasympathetic (craniosympathetic)

rest and digest (calm)

Outflow only occurs at S2-S4 and CN III, VII, IX, X

• long, myelinated preganglionic fibers

• short, unmyelinated postganglionic fibers

sympathetic (thoracolumbar)

flight or flight (increase HR, slows digestion, sweat, etc)

Outflow only occurs T1-L2 

• short, myelinated preganglionic fibers (don’t travel far to reach ganglion)

• long, unmyelinated postganglionic fibers

dual innervation

organ receives intervention from the visceral and somatic pathways

• pupil dilation/constriction

• vasodilation/constriction

adrenergic 

sympathetic affect in dual intervention 

• pupil dilation 

cholinergic

parasympathetic affect in dual innervention

• pupil constriction