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Introduction – Gastrointestinal Motility

by Thad Wilson, PhD
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    00:02 Hello! Today, we’re going to talk about GI motility.

    00:06 We’re going to cover a number of important topics and the first of which is to try to explain how GI motility works.

    00:12 And this will include three important aspects including peristalsis, slow waves, and migrating motor complexes.

    00:21 Then, what we’re going to do is talk about how swallowing is initiated and controlled.

    00:26 And finally, we will explain how gastric emptying works and how this process is regulated and controlled.

    00:33 So let’s go back to our GI functions and determine which ones we’re going to cover today.

    00:39 And that is excretion, storage, and most importantly, motility.

    00:46 To discuss motility, we need to go through a little bit deeper on the various layers of the GI tract.

    00:53 These layers go from the mucosal layer, which is the most innermost, to the serosal layer, which is the most outermost.

    01:01 So the nerves are going to be controlling the muscular activity, the mucosal cell or layer, then that is the layer of muscle around the mucosal layer.

    01:13 Then we have a couple of plexus.

    01:15 The Meissner plexus and the submucosal plexus.

    01:21 The submucosa, and this is important, this circular layer of muscle.

    01:26 And finally, the Auerbach complex, and the longitudinal layer.

    01:32 So you notice there were three different layers of muscles in the GI tract.

    01:36 And this will be important in being able to squeeze the GI tract together and to be able to push items along this particular tube.

    01:47 And of course, the final layer is the serosa.

    01:52 Now, how this process works is through an intricate process known as persitalsis.

    01:57 Now, peristalsis is a way of coordinating muscle contraction and this is smooth muscle contraction.

    02:05 So you’re going to use acetylcholine at the site to cause a contraction.

    02:11 We need to relax the area that is in front of that contraction.

    02:15 And that is done via nitric oxide or vasoactive intestinal peptide.

    02:21 And these are released right where you need to relax that particular portion of the muscle.

    02:29 Then, what happens is the food stuff is pushed along because you have a contraction and a relaxation.

    02:36 And of course, everything is going to follow to the area of lower pressure.

    02:40 This whole process is controlled either by the parasympathetic nervous system or the enteric nervous system depending on if it is centrally driven or if it is a local reflex.

    02:51 The central driven is the parasympathetic nervous system and the local reflex is the enteric nervous system.

    02:59 Now, besides peristalsis, the other important thing are these sphincters.

    03:04 Sphincters will be areas that are constricted during rest and this prevents movement from one area of the GI system to another.

    03:13 And what mediates this constriction are enkephalins.

    03:17 Often though, vasoactive intestinal peptide will be the relaxation agent for those particular sphincters.

    03:25 So when you want to open them, you would give the VIP or nitric oxide some time to be mediated to cause relaxation.

    03:35 Now, the other motility issues that need to be discussed besides peristalsis and contraction of sphincters are a lot of the movements are not to just to move things through the GI tract, but rather to mix things up.

    03:50 Because we have all these secretions in the GI system.

    03:53 What you need to do is make sure they’re well mixed and so the enzymes can work in the appropriate spots.


    About the Lecture

    The lecture Introduction – Gastrointestinal Motility by Thad Wilson, PhD is from the course Gastrointestinal Physiology.


    Included Quiz Questions

    1. Acetylcholine
    2. Nitric oxide
    3. Vasoactive intestinal peptide
    4. Enkephalin
    1. Mucosa layer
    2. Serosa layer
    3. Longitudinal muscle layer
    4. Circular muscle layer
    5. Layer of nerve plexus
    1. Sphincter relaxation
    2. Sphincter constriction
    3. Gastrin release
    4. Gastrin inhibition
    5. Decreased gastric motility

    Author of lecture Introduction – Gastrointestinal Motility

     Thad Wilson, PhD

    Thad Wilson, PhD


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