Autonomic Nervous System


1. Understand the basic functions of the autonomic nervous system (ANS) underlying "flight and flight" and "rest and digest" behaviors.
The ANS keeps the balance between Fight and Flight, and Rest and Digest behaviors, known as homeostasis. They are seen as two opposing systems correcting eachother by feedback inhibition. Both systems are excitatory and inhibitory. The sympathetic nervous system is responsible for the former behaviors, and the parasympathetic system the latter.

2. Be able to identify the three main divisions of the ANS, as well as their major functions, preganglionic inputs, postganglionic outputs, and targets.
System
Major Function
Preganglionic Input
Postganglionic Output
Target
Sympathetic
Fight or Flight response, Visceral Pain afferents
Skin: IML horn of SC, T1-L3
Head: Brain to SCG
Viscera: CNX to SCG or Thoracic ganglion
Named ganglia to peripheral nerve, prevertebral or paravertebral ganglia, travel along BV's
Skin, Head, Viscera
Parasympathetic
Rest and Digest response
Head: CN nuclei (Edinger-Westphal nucleus for CNIII in midbrain, Lacrimal and SS nuclei in Pons, ISN in Medulla)
Viscera: Dorsal Motor Nucleus of CNX in Medulla, Sacral region IML to sacral roots
Named ganglia:Ciliary, Pterygopalatine, Submandibular, Otic etc)

Input to nucleus of Solitary Tract
Head, Viscera
Enteric
Digestive regulation of the GI tract
Parasympathetic: Vagal nerve and Pelvic Splanchnics

Sympathetic: Pre and Paravertebral ganglia from T1-L2
Consists of two plexuses in the wall of the enteric system, Myenteric and Submucosal plexus
GI tract


3. Be able to describe the sensory components of the ANS.
Receptors bring action potentials to the CNS from either free nerve endings or specialized sensory organs. Axons carrying information about pain and pressure generally travel with sympathetics (thoracic and lumbar splanchnics), except for some pelvic information, carried with the pelvic splanchnics and therefore considered parasympathetic. Axons carrying mechanosensory information travel in the vagus nerve or the pelvic splanchnic nerves, projecting to the solitary tract and nucleus in the CNS.


4. Be familiar with the chemistry of synaptic transmission in the ANS and its physiological implications.

Ganglionic transmission is done via fEPSP's, using nicotinic cholinergic receptors. In some cases a slow EPSP can also be generated by sustained production of Acetylcholine, leading to binding to muscarinic receptors, causing a G-protein mediated inhibition of K+ channels. Neuropeptides can also effect a slow EPSP through similar mechanisms.
Postganglionic transmission uses cholinergic transmission, in addition to neuropeptide and NO release. Transmission is mediated by mAchR's, peptide receptors and the direct action of NO on cells. Posganglionics also produce norepinephrine, having an antagonistic effect on mAchR's.
Through ganglia, nicotinic AchR's are used for transmission, with some action of neuropeptides.

5. Understand the concept of referred pain.