Autonomic Nerves of Abdominopelvic Organs: Introduction

by James Pickering, PhD

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    00:01 In this lecture I am going to talk about the autonomic nerves of the abdominopelvic organs.

    00:09 Now this area of anatomy, the autonomic nervous system, and specifically the autonomic nervous supply to the gastrointestinal organs.

    00:20 can be a little bit complicated. And many students that I teach often struggle with understanding this. So we are going to have a look at some important definitions first.

    00:31 Have a look at the overview of the autonomic nerves of the abdominopelvic organs; because that's really important to understand the basic principles before we go onto supply the specific nerves of the stomach, small intestine, large intestine the rectum, anal canal and the reproductive organs.

    00:53 Towards the end we will then indicate why good understanding of the autonomic nervous system is important for the function of the body, maintaining the internal environment and also for a phenomena called referred pain.

    01:09 And we mentioned that at the very beginning when we talked about to with regard to appendicitis and we will come back to it. And hopefully this time we will make more sense now we've understood the nerve supply, both somatic and autonomic.

    01:24 So the autonomic nervous system controls the activity of the internal viscera.

    01:30 So we are not able to alter this in any way We can't stand or sit and actively increase the rate of peristalsis.

    01:42 We can actively move our body, we can make biceps contract, we can stand up, we can walk.

    01:48 But we can't alter the amount of pancreatic juice that the pancreas releases.

    01:53 The amount of bile that liver produces.

    01:56 This is all done via our autonomic nervous system and its done without our conscious; without unconsciously being aware.

    02:05 So generally with regard to the abdominopelvic organs the sympathetic division of the autonomic nervous system decreases its general activity.

    02:15 So it's going to decrease the rate of peristalsis.

    02:18 It's going to reduce the blood supply to the organs.

    02:22 It's going to reduce the secretions of pancreatic juice.

    02:26 The parasympathetic will do the opposite.

    02:28 It is going to increase activity, so enhance digestion.

    02:33 It is going to increase peristalsis, dilate blood vessels to these organs, and increase the production and release of the pancreatic juice.

    02:42 We will explore the specific roles of these each of the organs as we go through.

    02:48 So some important definitions.

    02:51 The sympathetic part of the autonomic nervous system is going to originate from the thoracolumbar part of the spinal cord. Remember the spinal cord can be split into cervical thoracic, lumbar, sacral, the coccygeal segments.

    03:10 But if you are on an autonomic nerve and you are leaving the spinal cord it's going to be from the thoracolumbar region.

    03:19 Overall, as I have mentioned previously, the sympathetic is involved in the fight or flight response.

    03:25 So increase activity of your heart, increase respiratory rate and it does this at the consequence of reducing the activity of the GI tract.

    03:35 The parasympathetic part of the autonomic nervous system is going to originate from the craniosacral part of the brainstem and spinal cord.

    03:45 So it comes from the medulla. We have some key autonomic parasympathetic nerves that radiate from the medulla region of the brainstem and other parts within the brainstem. But for the abdominal region, the vagus nerve is important.

    04:02 And it's involved in the rest and digest. So when you are relaxing at home, it's going to be involved in increase in peristalsis, dilating the blood vessels and increasing the release of gastric juice, pancreatic juice.

    04:18 The autonomic nervous system works by way of two nerve fibers.

    04:22 A nerve fiber that sits in the spinal cord or the brainstem and this is known as the pre-ganglionic fiber.

    04:31 And it leaves the central nervous system and it passes to an autonomic ganglia.

    04:37 Ganglia, collection of cell bodies in the peripheral nervous system.

    04:41 So these fibers pass from the spinal cord of the brainstem to an autonomic ganglion.

    04:48 At this autonomic ganglia, it's going to synapse with a post-ganglionic fiber.

    04:55 And this post-ganglionic fiber is going to pass from the autonomic ganglia to the target organ. So we have a two fiber chain. From the central nervous system to the autonomic ganglia and then from the autonomic ganglia, to the target organ.

    05:15 We have two different types of autonomic ganglia. I just want to explain here. We have one known as pre-verterbral ganglia.

    05:26 These assume the same position as those pre-vertebral lymph node which we spoke about.

    05:31 And these are positioned anterior to the aorta.

    05:34 They were collection of cell bodies that are aggregated around the three unpaired visceral arteries of the aorta. So we have the coeliac ganglia the superior mesenteric ganglia, the inferior mesenteric ganglia.

    05:50 These ganglia are going to be receiving the pre-ganglionic fibers And at these ganglia they will synapse with the post ganglionic fiber that will then extend to the target organ.

    06:05 These occur with the pre-verterbral (the pre-aortic) autonomic ganglia We also have para-vertebral or para-aortic autonomic ganglia and these are a connected series of ganglia either side of the vertebral column and you probably known them as the sympathetic chain.

    06:25 Run either sides of the vertebral column and these also can receive pre-ganglionic fibers.

    06:34 And a synapse can occur here and then pass to the target organ.

    06:39 Now this arrangement typically happens in the thorax.

    06:43 For the abdomen we are really going to concentrate on the pre-vertebral, pre-aortic ganglia.

    06:52 We're then going to talk about the autonomic plexuses.

    06:55 A series of plexuses that surround again, the unpaired visceral arteries of the aorta.

    07:02 So we have an autonomic plexus.

    07:05 This contains a collection of autonomic fibers say, the coeliac plexus and these typically will be para-sympathetic and sympathetic in nature.

    07:17 We will also hear the word splanchnic used a-lot. Now this word just refers to an autonomic fiber that's passing to the organs of the trunk.

    07:29 It can be a sympathetic like a lumbar splanchnic nerve.

    07:35 Or it can be para-sympathetic like a pelvice splanchnic.

    07:39 But splanchnic just refers to an autonomic fiber.

    07:46 The final kind of definition that i want to go is the periarterial plexuses.

    07:50 As you will see the autonomic plexus is associated with the coeliac trunk, superior mesenteric artery, inferior mesenteric artery.

    08:00 The best way for these autonomic fibers to pass to their target organ is the piggyback on the blood vessels.

    08:10 So if the artery is going to the organ, then these fibers will run around the artery to reach their target organ and these again can be sympathetic or para-sympathetic.

    08:23 So let's have a look at the anatomy rather than just the definitions.

    About the Lecture

    The lecture Autonomic Nerves of Abdominopelvic Organs: Introduction by James Pickering, PhD is from the course Pelvis.

    Included Quiz Questions

    1. Enhanced digestion
    2. Increased heart rate
    3. Decreased peristalsis
    4. Constriction of blood vessels
    5. Decreased production of pancreatic secretions
    1. Vagus
    2. Abducent
    3. Glossopharyngeal
    4. Hypoglossal
    5. Trigeminal
    1. Anterior to the aorta
    2. Posterior to the aorta
    3. Superior to the aortic arch
    4. Inferior to the aortic arch
    5. Lateral to the aorta
    1. Thoracic and lumbar spine
    2. Cervical and thoracic spine
    3. Sacral and coccygeal spine
    4. Lumbar and sacral spine
    5. Lumbar and cervical spine

    Author of lecture Autonomic Nerves of Abdominopelvic Organs: Introduction

     James Pickering, PhD

    James Pickering, PhD

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