Let’s start by introducing the general layout of the human brain. This layout is present from birth and is consistent in all animals from very primitive species all the way up to humans.
At the bottom an adult human brain, we have the spinal cord which is bringing information into the brain and sending it back to the body. One thing to remember is that the closer we are to the spinal cord, the more basic functions are. We then have the hindbrain and the midbrain. And finally you have the forebrain. Look how large that forebrain is in humans. This is where all the thinking, emotions and memories are happening. So you can see as you move from bottom to the top of your brain you change from basic functions that are trying to keep us alive to much more complex functions.
We are going to cover the major parts of the brain. You should always be thinking what’s the name of each part of the brain? Where is it? What’s its function? What does it do?
If you start with a basic brain plan, four structures jump out at you. You can see the brainstem, then you have the cerebellum at the back of the brain. We then have a structure called the thalamus and hypothalamus below it, and finally we have the cerebrum in the upper part of the brain.
The brain stem is divided into three individual structures. If you start at the bottom, you have the medulla oblangata, then you have the pons and at the top of the brainstem you have the midbrain. These three structures make up what we call the brainstem.
That’s the structure. What’s its function? It does two things. First, it controls our basic needs like keeping the heart beating, keeping circulation going and digestion working. So you can see any damage to the brainstem is going to be catastrophic. The second thing it does is it sends signals to the rest of the body and receives them back. It has sensory information coming in from different parts of the body and it issues commands to make the body move. It filters and routes this information to make sure it gets to the right places.
Behind the brainstem at the back of the brain, we have the cerebellum - the “little brain”. Its function is “motor control”. When you play sports it is the cerebellum that gives you coordination and balance. It also gives you motor memory. So when you ride a bike and you remember to pedal and don't lose your balance it is thanks to your cerebellum.
Further up and above the brainstem, right there in the middle of your brain is the thalamus. Imagine a busy train station like grand central station or London waterloo, where trains are constantly arriving and departing. Like a busy station, the thalamus is constantly receiving messages from all over the brain. It has to sort them and make sure they are relayed to the correct destination in the brain.
Right below the thalamus is the hypothalamus, which sits above the roof of your mouth, near the pituitary gland. What does this do? Well it maintains homeostasis. Via the pituitary gland, it releases hormones around the body and controls body temperature, thirst, and sleep.
If we move up further we reach the cerebrum, which is responsible for the integration of complex sensory and neural functions. It contains billions of neurons and is responsible for performing higher functions like interpreting touch, vision and hearing, as well as speech, emotions, thinking, and control of movement.
We have been considering the brain from a side view. But if you flip the brain 90 degrees and look at the brain from the front you can see that the brain actually consists of two halves. And these are called the cerebral hemispheres. There is a right and left hemisphere. They are connected by this mass of nerves called the corpus callosum. There is a tendency in the brain for lateralisation. We put some things on the left side of our brain like mathematical reasoning and language and other functions we put on the right side of our brain, like face recognition.
Now if we look right below the corpus callosum we find this area called the basal ganglia. This collection of nuclei inside here are called the basal ganglia. What are nuclei? Well they are a collection of cells with the same functions. The main function of the basal ganglia is to coordinate all of our movements. And if this area stops working, people will unfortunately end up with Parkinson's disease.
Now we have arrived at the cerebral cortex. That makes up about 80% of the brain. And it is divided into different lobes. So if we start at the front of the brain at what is called the frontal lobe. What’s its function? Well it is the boss, the “control centre” of the brain. It has “executive functions”. By interacting with the rest of the brain, it controls a lot of our movement and emotions. And it is where our personality lives. People who have damage up there have huge changes to their personality and emotional swings.
If we move back to the parietal lobe. What does that do? It is mainly involved in sensation and how we interact with the world around us. Inside this area we have the somatosensory cortex. When you map this area along the cerebral cortex, you can see it devotes huge amounts of the brain surface area to parts of the body like your fingers, your tongue, your lips. In other words, we have more neurons and a lot more sensory information coming in from more sensitive parts of the body. If you have damaged this part of the brain, you might end up ignoring part of your body or even one side of the world around you.
Then we can move the back here to the occipital lobe. It is the only lobe with a single, unitary function: vision! It produces your visual perception of everything! The fact that so much cortex is devoted to vision shows what an important function it is for us. Damage to this part of this part of the brain would effectively make you blind to everything on one side of the world.
Then we move to the temporal lobe. This lobe is important in language, in hearing, recognising faces and emotions and also very important in memory. Damage to this part of the brain can cause complete amnesia, where you are unable to form any new memories.
So you can see that each lobe is associated with different functions.
That is the brain!
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