Parasympathetic Nervous System (PNS): Organization

00:01 Now, let's look at the organization of the parasympathetic nervous system.

00:06 And remember, this is characterized by incredibly long preganglionic fibers that go all the way to the target organ.

00:14 Then within the target organ, they have very short postganglionic fibers.

00:20 So here we can see the dorsal nucleus of the vagus nerve.

00:22 And this gives rise to the key parasympathetic nerve of the body.

00:27 The vagus nerve, cranial nerve 10.

00:30 So here we have the vagal nerve leaving the brainstem and it passes all the way down the thorax through the diaphragm, and it's giving rise to a long preganglionic plexus.

00:41 Once this preganglionic nerve has given rise to the postganglionic nerve, this is forming that myenteric plexus within the muscle wall.

00:50 So, a network of nerve fibers within the actual muscular wall of the GI tract.

00:56 This then leads on to what's known as the enteric nervous system.

01:00 And that's the deep neural structure of the GI tract.

01:03 We don't need to worry too much about it right now.

01:06 But essentially passing towards the foregut and the midgut regions, we have a whole series of myenteric plexus is associated of all of these organs.

01:17 And they're formed via the long preganglionic nerves that sit in the vagus nerve.

01:23 The pelvis and the hindgut aspect and mostly controlled by the sacral part.

01:29 Remember, is the cranial sacral outflow, that is parasympathetic in nature.

01:33 And these gives rise via the lateral horns to pelvic splanchnic nerves.

01:39 These leave from the sacral aspects of the spinal cord and give rise to long preganglionic fibers, then they will again form their plexus around the target organ.

01:51 Organization of the parasympathetic nerve.

01:54 So, we have the cranial part, the parasympathetic nuclei leaving the brainstem that's going to go and innovate in the head and neck region.

02:02 The vagus nerve specifically is going to the liver, the gallbladder, etc.

02:07 All the way up to the last two thirds of the transverse, the first two thirds of the transverse colon.

02:14 Because the sacral part via the pelvic splanchnic nerves is going to supply the hindgut.

02:19 So the last third of the transverse colon descending sigmoid rectum, and the pelvic organs via these pelvic splanchnic nerves.