The vagus nerve sends projections to much of the body visceral organs. It
originates in the brain stem and is very important in the control of heart
rate, gastric motility, digestive, and metabolic activities. When the
vagus sends messages to the heart, the heart rate slows. When the vagus
sends messages to salivary glands, they secrete saliva. Vagal stimulation
of the pupil causes the aperature to close (mydriasis.)
One common term used in conjunction with vagal function is vagal tone.
Increased vagal tone results in a slower heart rate, salivary secretions,
and pupillary constriction. Decreased vagal tone has the opposite effects.
It is possible to inhibit the actions of the vagus which would decrease
vagal tone, but that is probably not what is implied by vagal inhibition.
You see vagal inhibition a potentially sloppy phrase. Vagal inhibition of
the heart slows the heart rate. Inhibition of the vagus accelerates the
At 7:47 PM +0100 4/11/99, Peter Moss wrote:
>Hi, could anybody please give me a brief description of what this is?
>Preferably in non-technical language,
Richard Hall, Associate Professor of
Comparative Animal Physiology
Division of Sciences and Mathematics
University of the Virgin Islands
St. Thomas, USVI 00802
rhall at uvi.edu