Autonomic Nervous System

• SNS: Skeletal muscle
• ANS: Cardiac & smooth muscle and glands

SNS: One neuron system

• ANS: Two neuron system
• Presynaptic- before synapse
• Postsynaptic- after synapse

SNS: Acetylcholine (excitatory)

• ANS:
• Presynaptic neuron- Acetylcholine (excitatory)
• Postsynaptic neuron-Varies between sympathetic (epinephrine) and parasympathetic (acetylcholine); either excitatory or inhibitory

Autonomic ganglion: collection of nerve bodies

Adrenal medulla: like a ganglion; does not develop axons but still produce epinephrine which has sympathetic effects on target structures

• Routine maintenance
• "Rest & Digest"

• Mobilization & increased metabolism
• "Fight or Flight"

More widespread than PNS and the only function not stimulated is digestion

• Symp: thoracolumbar division (T1-L3)
• Para: brain (CN 3,7,9,10) and sacral spinal cord

Symp: Presynaptic (short); postsynaptic (long)

Para: Presynaptic (long-synapses @ destination); postsynaptic (short)

Symp: close to spinal cord (sympathetic chain & prevertebral/collateral ganglia) 

Para: in/near visceral effector organs

• Only innervates internal organs
• Generally inhibits or slows down body functions
• Only major body function not inhibited in digestion (turns it on)

• Terminal ganglia
• -Named ganglia (CN 3,7,9 synapse here)
• -Intramural (near/in wall of organ)

Oculomotor n (CN 3): Smooth muscle in eye

Facial n (CN 7): Lacrimal, submandibular, sublingual glands

Glossopharyngeal n (CN 9): Parotid gland

Vagus n (CN 10): Almost every organ in thoracis & abdominal cavity (heart, lungs, liver, gallbladder, stomach, small intestine, pancreas, & proximal 1/2 of large intestine

• Fibers of presynaptic neurons travel through ventral root -> spinal n -> ventral rami
• Exit ventral rami as pelvic splanchnic n (S2-S4)

Distal 1/2 large intestine & pelvic viscera (urinary bladder, ureters, & reproductive organs)

• Paravertebral ganglia on sympathetic chain
• Prevertebral/Collateral ganglia on abdominal aorta

Intermediate horn where the SNS neural bodies are

• Located on both sides of the vertebral column
• -Extend from cranial base to coccyx

Paravertebral ganglia joined to spinal nn by white & grey rami communicantes (on/off ramps of highway)

White rami (on ramp): presynaptic fibers; found at T1-L2; myelinated fibers

Synapse on the chain

Grey rami: postsynaptic fibers; found along all levels of spinal cords; unmyelinated fibers

• Presynaptic fibers exit spinal cord through ventral root
• -> spinal nn
• -> White ramus communicans
• -> paravertebral ganglia on sympathetic chain

• 1. Synapse at paravertebral ganglia at same level
• 2. Synapse at paravertebral ganglia at a different level
• 3. Does not synapse on chain: will synapse at a prevertebral/collateral ganglia on abdominal aorta (synapse on blood vessels)

• Both visceral and somatic sensory fibers enter the spinal cord together
• Visceral pain may radiate along somatic pathways (referred pain)