Anatomy of the Brain (Nursing)

00:01 All right. Let's look at the first part of the central nervous system, the brain.

00:06 The majority of the brain that we can see here is composed of something called the cerebrum.

00:12 It occupies the majority of the volume of the brain.

00:16 But sitting just inferior to it is a smaller portion called the cerebellum.

00:23 And that's just basically saying, smaller cerebrum.

00:28 And finally, we have the brain stem here and that's what's going to connect the brain to the spinal cord.

00:37 When we look at the surface of the brain, we see there are a lot of bumps and crevices and each bump we refer to as a gyrus or the plural would be gyri and in between adjacent gyri are a little valley called the sulcus.

00:54 The plural there will be sulci. So, the brain is thrown into these gyri and sulci.

01:01 And again, in the brain, at least, in the cerebrum in particular, the outer part or cortex, cortex means bark.

01:10 So, cortex, whenever you see that, it means it's the outer part of something.

01:13 That cortex or outer part of the brain here is composed of gray matter.

01:19 And then, deep to that is where we find the white matter.

01:23 Again, this all goes back to the microanatomy where we have the nuclear components or the cell bodies found in the gray matter and the myelinated of axon parts in the white matter.

01:36 Here, we have a sagittal view right through the midline to see a few more details.

01:42 So, again, we have the brain stem which is connecting the rest of the brain to the spinal cord.

01:50 Superiorly, we have the midbrain. Then, we have the pons.

01:56 And then, the last part is the medulla oblongata or in this context, simply the medulla, beyond which we have the rest of the spinal cord. Posterior to the brain stem, we have the cerebellum.

02:10 Let's take a closer look at the cerebrum. The cerebrum is relatively large and can be broken down into smaller components that we call lobes.

02:21 Interiorly, we have the frontal lobe. Posterior to the frontal lobe, we have the parietal lobes.

02:29 Laterally, we have the temporal lobe and posteriorly, we have the occipital lobe.

02:39 And when it comes to these brain lobes, they actually correspond roughly to the skull bones that sit on top of them.

02:46 For example, sitting around the frontal lobe, we have the frontal bone.

02:52 We have the parietal lobe sitting just beneath the parietal bones.

02:57 We have the occipital lobe sitting below the occipital bone.

03:02 And finally, we have the temporal lobe sitting behind our temporal bone.

03:09 Furthermore, even though the brain is very complicated, very interconnected and many different areas have an influence on any given function, there are certain areas of the brain that have greater control over certain functions than others.

03:25 For example, the frontal lobe has a greater control over consciousness and many higher order functions are carried out by the frontal lobe such as planning, development, behavioral choices in the frontal association area.

03:41 We also have areas for speech and something called the motor cortex that we'll look at in greater detail in a little bit.

03:49 Similarly, the parietal lobe has a great role of movement in stimulus perception.

03:55 For example, there's the somatosensory cortex which is a very important role in sensing the outside environment.

04:04 Also, it's areas for taste and speech as well as reading and comprehension.

04:11 The occipital lobe is very important for vision and has direct connections to visual structures more anteriorly in the head.

04:22 When we receive visual inputs directly into the occipital lobe as well as areas for processing that visual input.

04:32 The temporal lobe has a very important role in speech recognition.

04:36 And therefore, also has a lot to do with hearing.

04:40 And the processing of hearing or the auditory association area as well as smell.

04:48 The brain stem compared to the cerebrum has what we might consider lower order or more basic functions.

04:56 For example, things like the control of breathing, something that's very basic and essential but not so complicated like thinking, planning, and making decisions.

05:09 The cerebellum is really important for movement coordination, even though a lot of movement under voluntary control can be traced back to areas of the cerebrum, coordinating movement and position and space is a very complicated process and without the cerebellum, it would make for very uncoordinated movements and very difficult ability to walk, speak, and create other sorts of complicated movements.

05:39 Speaking of movements, let's focus in on the motor cortex for a second.

05:46 As well as it's nearby somatosensory cortex. The motor cortex is this gyrus here that is the posterior most portion of the frontal lobe and the somatosensory cortex is the anterior most gyrus of the parietal lobes.

06:04 And together, they actually map out pretty well to the various parts of the body with regard to motor control and sensor input. And what this little image is here is something called a homunculus which is a graphical representation of the areas of the body that map to these portions of the motor or somatosensory cortex and you can see, it's not proportional to regular anatomy and that's because certain areas have more nerves in them and therefore, occupy more parts of the motor and somatosensory cortex.

06:45 For example, you can see the hands are much larger than the feet.

06:49 And that makes sense, for example, in the motor cortex, there would be much more control over hands and hand movement than there would be feet.

06:59 Think of all the complicated things you can do with your hands, for example, writing or typing, or doing things like that that you can't really do with your feet.

07:09 The face is much larger than the rest of the body and that makes sense because there are a lot of fine movements in the face as well as a lot of sensation.

07:19 The face is much more sensitive than for example, the knee cap, right? The lips in particular and the tongue are very sensitive.

07:30 So, there's going to be a large portion of the somatosensory cortex devoted to them.

07:35 And with the tongue as well, the motor cortex because the tongue can move in all sorts of directions with many muscles making up the tongue, there's going to be a lot of nerves that control its movement.

07:48 Similar, the larynx. The larynx is a fairly small part of the body but the process of vocalization involves very fine control of muscles of the larynx.

07:59 Therefore, it's going to be a disproportionate part of the motor cortex compared to some other parts of the body with more basic movements.