Autonomic Nervous System
  Pg 1: Overview | Pg 2: Divisions | Pg 3: Parasympathetic | Pg 4: Sympathetic | Pg 5: Dual Innervation
Divisions of the ANS

First we will take a look at the autonomic divisions of the CNS. The parasympathetic (also known as cranialsacral) division provides a protective function for the body, and generally operates to maintain and replenish bodily reserves. The sympathetic (or thoracolumbar) division functions generally in utilization and expenditure of bodily reserves.

The colored regions of the brain and spinal cord indicate the CNS areas from which the sympathetic or parasympathetic divisions begin. Note that they have their own specific territories. These regions are where the cell bodies of the preganglionic neurons lie. Likewise, the similarly colored peripheral structures are the sites where the collections of cell bodies of the postganglionic neurons are found. These are the autonomic ganglia. They are either sympathetic or parasympathetic.

The Parasympathetic Division controls:

  • meiosis - protects retina from excess light
  • GI motility - increases to promote digestion and absorption of nutrients
  • slows heart rate
  • opens sphincters (stomach, rectum, bladder)
  • causes salivary glands and mucosal glands to secrete
  • vasodilation in erectile tissue of penis and clitoris - erection
  • *Operates all the time.

The Sympathetic Division controls:
  • mydriasis - opens pupil to let light in
  • accelerates heart rate
  • increases blood pressure
  • increases blood glucose
  • dilates bronchioles
  • ejaculation - contracts smooth muscle of associated penile structures
  • *Operates all the time and capable of massive response in emergencies - "sympathetic discharge" in the "flight or fight" reaction


Copyright © 2006 - University of Pennsylvania School of Veterinary Medicine, All rights reserved.
Faculty: Dr. Richard Miselis, Dr. Peter Hand
Students: Natalie Fickel V'12, Ryan Donahue V'09, Cara Catanese V’08, Rebecca Wolf V'06, Keith Javic V'03, Ken Bixel V'99, Russel Howe-Smith V'97