Introduction to the Nervous System (Nursing)

00:01 Now, we're going to take a look at the nervous system and start looking at some brain anatomy.

00:07 Now, to be fair, the nervous system is very complicated.

00:11 So, we're really just going to focus on the major components of the nervous system.

00:16 In particular, we're going to compare and contrast the key features of what's called the central nervous system or CNS and the peripheral nervous system or the PNS.

00:26 We're also going to talk about the coverings of the central nervous system which are called the meninges.

00:33 We're going to talk about something called cerebrospinal fluid that flows between the brain and spinal cord, talk about the definition of a dermatome or talk about the differences between various components such as the somatic and autonomic system as well as differences between sympathetic and parasympathetic nervous systems.

00:54 But first, in order to really understand the gross anatomy, we have to talk a little bit about the microanatomy.

01:00 And so, here, we have a very basic representation of a nerve where we have a cell body where the nucleus is held and then, a long projection called an axon.

01:15 And ultimately, the nervous system is made up of a lot of nerves and for example, in this cross-section of spinal cord, we see that there's two sorts of colors we can pick up on.

01:28 There's the gray part and there's the white part which we call gray matter and white matter.

01:35 And we can see this with our own eyes because of the difference in what's called myelination.

01:42 So, the cell bodies where the nucleus is held don't have myelin whereas the axons have myelin which has a lot of fat in them and that gives it this white appearance.

01:53 Therefore, when we look at a portion of brain or spinal cord, we can actually pick up on the areas that are going to have cell bodies versus axons just on the actual appearance of it.

02:05 And when we look at the cross-section of the brain, we actually see that the gray matter tends to be collected towards the outside.

02:14 And then, the white matter tends to be more focused on the inside.

02:18 So, to be fair, there are areas deeper into the brain that have gray matter as well.

02:23 In fact, we call those the deep gray. The spinal cord on the other hand is the opposite where we see most of the gray matter being on the inside and the white matter being on the outside.

02:37 Now, this myelin sheath that has this fat content allows us to see gray versus white matter in the brain and spinal cord has a very important role.

02:49 It's actually got several little gaps along the length of the axon which allow for something called salutatory conduction and long story short, what that means is it's allowing signals to propagate over very great distances in a very short amount of time which is a key feature of the nervous system.

03:09 Okay. So, let's talk about the components of the nervous system.

03:14 Well, first, we have the CNS or the central nervous system. And that's pretty straightforward.

03:20 It's composed of the brain and the spinal cord to which it attaches.

03:25 The peripheral nervous system or PNS is essentially everything else and that includes nerves that exit out of the skull called cranial nerves as well as all of the nerves that are branching off of the spinal cord, collectively called the spinal nerves. We can also divide the nervous system in different ways.

03:47 For example, we have something called the somatic nervous system which is the nervous system that's generally under our voluntary control and it's the stuff that controls our body.

03:58 Soma means body actually. So, it's sort of the body nervous system.

04:02 And we also have the autonomic nervous system and the autonomic nervous system is under involuntary control.

04:11 And so that controls a lot of things we can't control consciously or voluntarily.

04:15 For example, organ functions. Let's contrast the features of the CNS with the PNS.

04:24 So, as we said, the components of the central nervous system are the brain and the spinal cord and these are both incased in bone. And that makes a lot of sense.

04:35 They're very important. They need that extra level of protection.

04:39 But also, for the most part, the brain and spinal cord don't regenerate after damage.

04:45 So, it makes sense that they're going to have an added layer of protection.

04:50 And these are really for higher order functions. This is where information is analyzed and integrated.

04:58 In contrast, the peripheral nervous system is made up of all of the sensory and motor neurons throughout the body.

05:05 Sensory for picking up information from the outside world and motor is just what it sounds like the nerves that help us move our body.

05:15 Now, the peripheral nervous system is actually pretty good at regenerating after damage compared to the CNS.

05:22 So, it's not incased in bone.

05:25 And it's really relaying sensory information to the central nervous system, letting it process and then, it carries out commands that the CNS sends to the PNS.