Video: Introduction to the brain
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Your brain works very much like a computer in that, at its most basic level, it too uses a binary code of sorts. It either sends an action potential along a nerve or it doesn't. And this is what makes us capable of completing everyday functions, like digesting your food, contracting your muscles, and facilitating vision. Yep, our brains are definitely one mega supercomputer and we could spend days or even years talking about all of its capabilities. But, today, we're going to start with the basics as we look at an introduction to the brain.
Before delving into the details, let's take a minute to introduce what we'll be learning today. We’ll start by taking a general overview of the brain and see how it fits in with the rest of the body. Specifically, the relationship between the central nervous system, or CNS, and its peripheral counterpart will be examined. This will give us a really good idea of how the brain acts like the computer we saw in the beginning.
Next, the different functional components of the brain will be examined starting with the three parts of the brainstem which control the lowest most basic bodily functions like breathing and heart rate. Next up, we'll investigate the cerebellum and we'll see how it helps you with your smooth fine motor movements like what you would use in the dissection lab then we'll ascend both in position and function to look at the different parts of the diencephalon. This part of the brain does many things including acting as a mediator for the nervous system by receiving and processing information then sending it where it needs to go.
Finally, we'll reach the large convoluted mass that constitutes the cerebrum, or the telencephalon, and, as we'll see, this is where the most advanced functions take place, like critical thinking and voluntary muscle movements. We’ll also see how the cerebrum is organized into two hemispheres which are each made up of various lobes that have their own unique function, but more on that later. Finally, we'll put on our white coat and look at what we've learned from a clinical perspective.
So before getting into the nitty-gritty details, let's see where the brain fits in as an integral part of the nervous system.
So if you've been surfing our site, then you may already be familiar with this stimulating ins and outs of the nervous system, in which case, you already know that the brain, along with the spinal cord, belongs to the part of the nervous system known as the central nervous system. Here is where you find components that are essential to the functioning of the human body, many of which will be covered in this tutorial.
Outside of the CNS, like out in the limbs, is where you find the peripheral nervous system, which continually communicates back and forth with the CNS. Now the CNS, especially the brain, acts like a conductor as it controls the orchestra of signals that regulate the secretions, movements, and excretions all over the body. These signals are sent out via efferent motor nerves, much like how the computer at the beginning used its binary language to send out commands across the network.
The brain not only uses the peripheral nervous system to send messages, but also to receive them. For example, peripheral sensory nerves from your feet, eyes, and skin tell your brain that the sand is soft, the sun is bright, and that jumping into the ocean on a nice hot day feels so refreshing. We call the nerves that carry these signals afferent or sensory nerves.
This, of course, is just the beginning of the story. Let’s get into the good stuff and see what this organ is really capable of, starting with the brainstem.
To see the brainstem, we'll use this midsagittal view which is as if we cut the brain down the middle and looked at its internal structure. This little guy might not look like much, but in actuality, your brainstem is essential to your survival as it regulates most basic functions to stay alive. It's also responsible for acting as a relay, or highway, for those sensory signals we saw earlier that are going up to the cerebrum and motor signals heading down and out to the periphery. The brainstem is made up of three separate parts which are the medulla oblongata most inferiorly, the pons which is this middle part of the brainstem that appears to be bulging out, and finally, the midbrain situated at the most superior aspect of the brainstem. Let’s go ahead and look at each part in a little more detail.
The medulla oblongata, or sometimes just referred to as the medulla, is the most inferior aspect of the brainstem and is immediately superior to the spinal cord. The medulla is responsible for regulating some of life's most basic functions like breathing, dilating and constricting blood vessels, and swallowing.
Next up, we have the pons found immediately superior to the medulla. This part of the brainstem is appropriately derived from the Latin word for bridge as it spans the two halves of the cerebellum, which we'll look at in just a minute. It also plays a role in regulating your sleep cycle, so please limit your all-nighters and give your pons some rest.
The third and final and most superior part of the brainstem is the midbrain, and it's here where integration of sensory input from the periphery and motor output from the cerebrum occurs. To put it simply, this is what tells you to move when there's a bus that's about to hit you.
Next up, we have the cerebellum. So many moons ago, an anatomist studied the cerebellum and thought this small ovoid mass of grain white matter sort of looks like a little brain, and thus, the cerebellum got its name. You can find the cerebellum hiding behind or posterior to the brainstem, which we just looked at, and the cerebellum helps maintain muscle tone, balance, and posture by sending out involuntary signals to your peripheral nervous system. This means that you have no conscious control over these signals and it happens automatically.
The cerebellum also helps with fine voluntary coordinated movements, which you do have control over and these movements will come in handy for looking at some deeper brain structures in our next section. But, for the moment, let's use our cerebellum to pick up the scalpel, carefully dissect a little deeper, and check out the next area of the brain – the diencephalon.
This part of the brain is located deep inside between the brain stem below and the cerebrum above; therefore, you may hear the diencephalon sometimes referred to as the interbrain since it connects these two major portions of the brain. Its position allows it to work as a relay center by processing and directing signals for sensory information and autonomic functions between the brain and the periphery. You can almost think of it as a central hub for the brain that helps coordinate different systems.
The diencephalon itself contains many parts including the thalamus which is the largest part of the diencephalon and just inferior to the thalamus is the metathalamus and the posterior part of the pituitary gland which is intimately related to the endocrine system. As you could probably guess, the diencephalon is very functionally diverse since it works between so many different systems, but we're just offering an introduction here. Of course, for more details, go ahead and check out our page dedicated to all things diencephalon.
Okay, and finally, we come to the largest and most functionally complex part of the brain – the telencephalon. To make studying this three-pound organ a little easier, we're going to be dividing it up into its various lobes. So keep in mind that all of these lobes that we'll look at are bilateral – meaning they have both left and right counterparts one in each hemisphere. And these include the frontal lobe at the most anterior aspect, and posterior to the frontal lobe, we’ll have the parietal lobe, and all the way at the most posterior aspect of the brain is where we'll find the occipital lobe, and finally, we'll check out the temporal lobe which is situated near the ears.
Let’s dig a little further and see what each lobe is capable of.
Without even realizing it, you've actually been using your frontal lobe quite a bit throughout this tutorial to help hold your attention, keep you motivated, and engage you in critical thinking. Also contained within the frontal lobe is this prominent ridge called the precentral gyrus which contains the primary motor cortex. But don't let these big words overwhelm you. The take-home message here is that this area controls voluntary muscle movements, which allows you to do some pretty awesome dance tricks. Finally, one last important function of the frontal lobe is the production of speech, which is specifically orchestrated by a region known as Broca's area.
Immediately posterior to the frontal lobe is the parietal lobe. It's in this part of the brain where language processing occurs. Without this vital piece of brain tissue, you'd have no idea what I'm saying and I might as well be speaking an entirely different language. Also located in the parietal lobe is the postcentral gyrus, which contains the somatosensory cortex. Compared to the motor cortex that we saw in the frontal lobe, the somatosensory cortex controls all sensory perception that's coming in from the periphery, which is how you felt the fine sand between your toes while walking on the beach.
When you see the occipital lobe, you should immediately think vision. Though you're right, it does seem a little counterintuitive that the most posterior part of your brain is what controls and processes information from your eyes. I guess maybe we do actually have eyes on the back of our head.
To wrap up the telencephalon, let's have a look at the temporal lobe. One main function of the temporal lobe is the processing of auditory information that is received from the ear. Unlike the perplexing arrangement of the occipital lobe with the eyes, the temporal lobe’s function with auditory processing make sense as it lies so close to the ear. The temporal lobe is also involved in the comprehension of written and spoken language.
Okay, so let's now give you some clinical context to what we've just learned.
So one important thing to keep in mind about the brain is that even though it has these individual parts that we just learned, it's constantly working as one cohesive unit sending and processing signals between itself and the rest of the body. But what happens when a part of this signaling pathway stops working? Well, one thing that can cause this is a stroke, which is when there's a disruption of blood flow to a region of the brain depriving the nerve cells in that area of nutrients and oxygen. This can be caused by a blockage or rupture of a cerebral artery.
The symptoms of a stroke are then dependent on which region of the brain is afflicted. If, for example, an artery supplying the parietal lobe gets blocked, the patient may be present with a sensory deficit or perhaps may develop dyslexia or trouble reading even though they can clearly see the words. This symptom is called alexia and it makes sense when you consider that the parietal lobe is one area where language comprehension takes place.
A physician may suspect a stroke based on physical exam findings, but medical imaging is usually required to diagnose like the CT scan that we see here. Treatment largely depends on the location and severity of the stroke, but the primary goal is to restore blood flow as quickly as possible. Anticoagulant medications will likely be used to help break up clots, and if the clot is large, surgery may be required to remove it.
And just like that, you've now been formally introduced to the brain. Let’s take a quick look back at what we learned today.
So we started by looking at the brain's role within the body as an integral member of the central nervous system. We learned how the brain communicates with the peripheral nervous system by using efferent or motor nerves to send messages outward while also receiving messages via afferent or sensory nerves. Then we transitioned into identifying the parts of the actual brain starting with the brainstem. We saw that it has three parts – medulla oblongata, the pons, and the midbrain. Their functions were also introduced which primarily included functions that are essential to life like regulating breathing and the sleep cycle as well as integration of motor and sensory signals.
We then turned our attention to the posterior aspect of the brainstem to identify the little brain, which is the cerebellum. And as we saw, the cerebellum helps us make fine balanced coordinated movements, something that would certainly come in handy for a gymnast. As we made our way up the brain, we were introduced to the diencephalon, or the interbrain, and recall that this area has many parts that help relay signals for sensory information and autonomic function.
Finally, we reached the functional and positional pinnacle of the brain – the telencephalon – which we learned can be divided into hemispheres and further subdivided into the lobes. And we then went through and named each of the lobes being frontal, parietal, occipital, and temporal. We then went through each lobe and identified some of their primary functions.
And to wrap things up, we applied what we learned in the tutorial to the clinical scenario of a stroke, which is caused by a blockage of an artery that supplies the brain tissue. And we saw how different symptoms could manifest depending on which region of the brain was affected by the blood clot and a diagnostic tool such as a CT were introduced and treatment options such as surgery were discussed.
And that's a wrap for the basics of the brain tutorial. From all of us here at Kenhub, thanks for watching and happy studying.