The old brain

here I have two pictures of the brain this one is a whole brain this is what you would see if you could take the brain out of a person's skull and this side is the front of the brain this side is the back here's the top here's the bottom and so if you can imagine someone's eye being down here and their nose this is what you would see if someone was standing in profile on this side I have what you would see if you were going to take this brain and cut it in half down the middle so let's say I have I have a face and here's their eyes and here's their mouth this is what we would see if we could slice directly down the midline of a person's head and we refer to this type of slicing of the brain as a sagittal slice specifically this one is a midsagittal slice because it goes directly through the middle of the brain and these two images are human brains although other animals do have brains that look somewhat like ours other animals have brains that are not nearly as complex for some really simple animals their brains take care of the basic survival functions things like breathing and resting and eating and this changes as we move to different sections of the evolutionary tree and even though I don't really like to think of evolution having directionality I think it's pretty fair to say that brains get more complex as animals become more evolved so Mouse brains are more developed than fish brains and and sheep brains are more developed than Mouse brains and human brains are more developed than sheep brains but just because a brain is more developed doesn't mean that it doesn't have those earlier structures in fact as the brain increases in complexity it builds on itself so brain systems are constantly being build on top of old ones and so as one moves further inside of the brain one is getting to older and older structures and this has a couple of consequences it means that the things in the middle of our brain the oldest structures are also the simplest because they're the ones we would also share with really early animals so deep inside the brain is where things like breathing and sleeping or controlled however as we move further out so as we get to newer more evolved structures the tasks that these brain areas perform become more and more complex ending with the cerebral cortex which is the outer covering of the brain that you can see right here and we'll talk about all of the different levels of the brain but right now I want to talk about that old brain the brain that's in the middle the brain that we share with much simpler animals and this area of the brain has a couple of different parts one area is referred to as the brainstem and if we're looking at the brain from the side that would include this section and here with the brain split in half this is where the brainstem is located so you can see it's mostly covered by the brain when we haven't split our brain in two and the brainstem is split into two parts one is called the medulla and the other is referred to as the pons the medulla is this area that's right here and this area right here is called the pons the brain stem controls really basic functions things like heartbeat and breathing but it also serves as a crossover point for our bodies nerves and to talk about this I need to reference the fact that the right side of the brain controls the left side of the body and the left side of the brain controls the right side of the body and so in the brain stem nerves that are coming in from the left side of our body cross over and move to the right side of our brain and similarly information coming in through nerves from the left side of our body cross over and move to the right side of the brain and that occurs in the brainstem inside of the brainstem and you can't really see because it's covered but I'll draw this in anyway to let you know where it is is this structure referred to as the reticular formation and this actually extends up from the brainstem into other brain areas and the reticular formation does a couple of really important things first of all it acts as a filter so as information is coming in through the spinal cord part of it is filtered by the reticular formation which can then send important information to other brain areas specifically the reticular formation extends into an area of the brain known as the thalamus which we'll be discussing in a moment and that thalamus acts as a relay station for the brain sending information to different areas the reticular formation is also really important for our sleep/wake cycles or for arousal more generally stimulating this area of the brain when an animal is sleeping can cause the animal to immediately awaken and not just awaken but be alert at the same time if this area of the brain is damaged it typically results in the person lapsing into a coma so not only does it act as a filter but it also plays a role in our ability to be alert and aware of our surroundings so I just mentioned the thalamus so I might as well talk a little bit more about that now so the thalamus is located here above the brainstem and even though we speak of it as if it's one structure like most things in the brain they're actually two of them so there are two egg-shaped structures that sit side by side in your brain and as I mentioned before when talking about the reticular formation the thalamus acts as a relay station so in information from our senses from our eyes or our ears comes in it gets relayed through the thalamus before eventually moving on to the areas of the brain where they're actually processed so all of the sensory information goes to the thalamus before being routed to other areas of the brain the one exception to this is the sense of smell but everything else seeing hearing tasting touching all of those senses go through the thalamus the thalamus is also responsible for relaying information from the higher brain areas the information is routed down through the thalamus down through our brainstem and our spinal cord the last old brain structure that I want to talk about today is the cerebellum and that's the sort of squishy area that you see down here and it's over here in the mid sagittal slice of the brain and the cerebellum is about the size of a baseball and extends around our brain stem and it's involved in a number of very important tasks specifically it helps us coordinate voluntary movement so the cerebellum allows us to do things like run and kick a soccer ball at the same time when this area of the brain is damaged people's movements can be pretty jerky and awkward and before I go on I should note that you might have had some issues with our belém coordination at some point in your life as well because this is at least one of the areas of the brain that's affected when you drink alcohol and as you may know when people drink a lot of alcohol their coordinated movements tend to suffer they stumble around they have trouble putting their keys in their front door and so these are all the kinds of coordinated movements that the cerebellum is associated with I want you to take a moment to think about the tasks that are performed by these older brain structures and one thing that you might notice is that all of these things happen without our conscious awareness of them so all of these things are heartbeat and alertness and string all of our movements together all of these things happen outside of our awareness