00:01
So now, let’s talk through all these
different neural signalling molecules.
00:04
And it usually helps to
set these up as tables.
00:07
And this is one thing that
you’ll want start lining through
so you can make sure
you understand which
neurotransmitter does
what particular function.
00:17
The first one is acetylcholine.
00:19
This is released by the
parasympathetic nervous system.
00:22
And its primary functions
are increasing motility,
increasing secretion, and
increasing blood flow.
00:29
ATP is released by the sympathetic nervous
system, causing decreases in blood flow.
00:35
Calcitonin gene-related peptide
is released by afferents.
00:39
So these are not from the sympathetic
or parasympathetic nerves,
but from sensory
nerves that release
calcitonin gene-related peptide
to increase blood flow.
00:48
The next class are enkephalins
and enkephalins are released
by the enteric nervous system.
00:55
So this the local control and these
help to constrict sphincters.
01:00
And what this does is you
constrict a sphincter,
you prevent the food stuff from moving from
one area of the GI system to the next.
01:08
A great example of this
is the pyloric sphincter,
which is located in between the stomach and
the duodenum of the small of the intestine.
01:16
If you have it constricted,
you’ll have less food stuff
going from the stomach
into the small intestine.
01:23
Finally, we have gastric releasing
peptide and why this is so important
is it’s released by both the
parasympathetic nervous system
and the enteric nervous system and
this increases gastrin secretion.
01:34
And remember gastrin secretion is
important for increasing hydrogen ions.
01:41
The other last set of neural
signalling molecules we have
are norpinephrine released by
the sympathetic nervous system.
01:48
This decreases motility, decreases
secretion, and decreases blood flow.
01:55
Neuropeptide Y, also
decreases motility.
01:58
Substance P is released by
sensory afferents primarily,
but sometimes as well by the
parasympathetic nervous system.
02:05
And that causes increases
in blood flow.
02:10
And finally, we have
vasoactive intestinal peptide
and that increases both
motility and blood flow.
02:18
So these are all the different
neural signalling molecules.
02:22
You will want to identify both where they
come from and what function they have.