So we've looked at the stomach
and we've looked at the
autonomic nervous system
that supplies the stomach;
and how parasympathetic and
sympathetic fibers control it.
Well again the small intestine is
controlled by these autonomic fibers.
These parasympathetic and
sympathetic fibers which we
can see here. We have got
the blood vessels left on,
and in green you can see this spiraling
mesh, this coblet of autonomic nerves.
Again we will look at these
in more detail later
on with the individual
organ lectures become very
detailed and complicated. So we will
look at the autonomic supply
all together in a later lecture.
But simply again
the parasympathetic is
going to have the effect
of increase in the activity
of the small intestine.
So it’s going to increase the peristalsis
through the small intestine. It’s going to
facilitate blood passing towards
the small intestine allowing
for the nutrients to be absorbed.
And this again is done
via the vagus nerve, the
specifically the posterior trunk.
Sympathetic is going to be
associated with decrease in activity.
So for example if you are running a marathon,
you want to direct that blood to your muscles
so they can carry out their
function. You don't want to have
a lot of blood passing
to the small intestines.
You want to direct that blood for oxygen,
for nutrients going towards the muscles.
So the sympathetic part of the autonomic
nervous system for the small intestine
is going to reduce its activity.
And this is carried out
again by some splanchnic
nerves greater, lesser, least.
We will look at those in later
lectures in more detail.
And they form what’s
known as the superior
mesenteric plexus. This is a hub of nerves that
surrounds the superior mesenteric artery
and these nerve fibers pass
towards the small intestine
via the arterial supply and they
circle periarterial branches.