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

There is a dual innervation of most organs of the body by the sympathetic (on the left) and parasympathetic (on the right) divisions of the ANS.  In the figure below,  the connections of both systems with the hypothalamus and higher brain areas have been omitted.  Solid lines are preganglionic axons.  Broken lines are postganglionic terminals.  Shading indicates the distribution of the sympathetic nervous system.  The axons of preganglionic sympathetic neurons tend to be short because they project to a nearby structure, whereas the axons of the postganglionic neurons are long.  THis situation is reversed in the parasympathetic division.  Parasympathetic preganglionic axons must often travel considerable distances to reach their terminal ganglia of the thoracic, abdominal and pelvic viscera or the head ganglia of the head.

With dual innervation of viscera:

  • There is a sympathetic and a parasympathetic innervation of an organ.
  • They usually do the opposite functionally: one will inhibit and the other will excite.
    • miosis and mydryasis of the pupil
    • opening and closing of sphincters of the GI tract
    • speeding and slowing of heart rate

Some viscera get innervated by only a single innervation:

  • vaso-, pilo-, sudomotor function is only by sympathetic innervation


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