The Brainstem

Author: Haritha, Learner, The Integral School, Hyderabad

What often happens with subjects such as biology, is that long complex words tend to throw one off. If you come across words like ‘mesencephalon’ and ‘rhombencephalon’, your brain is likely to swear never to ever cross the biology aisle in the library again (there are exceptions of course). Not understanding words or even phrases can be very frustrating, but if you break down the information it can be easier to process. Coincidentally, the information I would like to break down for you is regarding the brain — the organ that indirectly causes you to flip the page whenever Greek or Latin terminology sprouts up.

With whatever prior knowledge we have, we most likely know that the brain looks very much like a walnut or pecan (If you do not know what a walnut or pecan looks like, believe me, it looks like a brain). In fact, the shell that encases the nut is very similar to the skull that protects the squishy matter inside. Before we get into the complicated terms, their structure and functions, it might be sensible to consider why the brain is in our head to start with. Would it make a difference if our brain was split into two parts, with each part in one hand or foot? The answer is that it would make a large difference! The brain’s most basic function is to keep us alive (breathing, heartbeat, etc related), which I will get into later. The second basic function that the brain is responsible for sensing our surroundings, through hearing, smelling, touching, tasting and seeing. Four of these sensory organs happen to be on/in our head — nose, eyes, ears and tongue. Since the sensations captured by these organs (or scientifically speaking, the sensory input) has to travel to the brain, our bodies have provided the shortest route possible. The brain is in our head because the efficiency of receiving sensory data is increased. Think of the brain as a manufacturing joint or factory. The raw materials need to be transported to the site in trucks that use roads. These raw materials represent the information we take in with our senses. If the road to the factory is very long, it will take longer for the product to be manufactured, but if the  road is very short, the process will be much more faster. The faster it is, the faster the products can be shipped out. In other words, the faster our brain receives sensory information, the faster we can react.

Now, as I promised in the beginning, let us get into the structure of the brain and break down a few biological terms. The brain is a complex organ that becomes more and more intricate the further in you go. The brain is divided into three sections based on the complexity of their functions : The Rhombencephalon or hindbrain, the mesencephalon or the midbrain and the prosencephalon or forebrain. The key to understanding complicated terms is to look up their etymology. The word ‘rhomb’ comes from the Greek word ‘rhombos’, meaning ‘turn around’. This could suggest that the hindbrain is the part of the brain around which all the other parts revolve (figuratively speaking). The prefix ‘mes’ comes from the Greek word ‘mesos’, meaning ‘middle’ and the midbrain is located in between the hindbrain and forebrain. The prefix ‘pros’ comes from the Greek word ‘prosō’, meaning ‘forward’ and true to its name, the forebrain is in front of the pack (both complexity and location wise). If you are wondering what the term ‘encephalon’ is, it is derived from the Greek word ‘enkephalon’ meaning ‘what is inside the head’ — the brain.

To start with, let us look at the brainstem (a fairly straightforward term). The spinal cord is connected to the walnut like part of the brain by the brainstem. For simplicity sake let us picture the brainstem as the entrance and beginning of the brain. The brainstem is the part of the brain that has the least complicated function (it has basic functions). Previously, the brain had been  pictured as a walnut, but to visualize the structure of the brain, including the brainstem, it is helpful to compare it to a mushroom — it has a stalk that grows into a hood. As the name suggests, the brainstem is the stem of the brain. It even looks like a stem and perhaps that is why it was named so. Pay close attention here as things are about to get slightly complicated — the brain stem is made up of three parts, the medulla oblongata, the pons and the midbrain. The word ‘Midbrain’ sounds familiar doesn’t it, that is because it is that very same part of the brain that is called the mesencephalon. Let me break this down a little further : The brainstem comes under the hindbrain and midbrain (rhombencephalon and mesencephalon). The medulla oblongata and pons are part of the hindbrain. The hindbrain also contains the cerebellum but that explanation will be reserved for later. The entire midbrain is also part of the brainstem.

The brainstem controls a multitude of things, all vital to our survival. Each part of the brainstem has a particular role to play in the entire system. Not to be selective or biased, but the brainstem does come under the first priority list. Our survival literally hinges on the state and efficiency of the brainstem. What are the first few things one needs to stay alive ? For a start, one needs to breath and needs the oxygen to be circulated throughout the body. The brainstem is responsible for controlling the cardiovascular and respiratory system (simply put, functions related to circulating blood and breathing). There are other parts of the brain that record our memories or allow us to learn new information, but if we could not breathe, it is rather pointless being able to remember that the first world war took place in 1914, or that you had a lemon cake for your fourth birthday. The brainstem may not have complex functions but it has very important functions. I don’t mean to pick sides, in fact the body is such a planned and integrated network that each function or part is crucial in the overall system. Think of the body as a machine, each cog and crank has it part to play, without which the entire machine would be defected. Even each tooth on the cog has to be aligned for the machine to operate at its optimum efficiency.

The brainstem does have many other functions, all of which we do not need to mentally think about. Functions related to pain sensitivity, alertness, awareness, consciousness, the respiratory system and the cardiovascular system (which the brainstem is responsible for) take place whether we give them thought or not. They are functions that occur independent of whether we will them to or not.

The brainstem is like a three legged stool, each leg representing a part of it — the medulla oblongata, pons and midbrain. The medulla oblongata gets its name from Latin and it literally means ‘elongated marrow/pith of plants’. The name is such because the medulla oblongata probably looks like vegetable pith that has been elongated. The medulla (short for medulla oblongata) is responsible for regulation of breathing, swallowing, sneezing, heart, blood vessel functions, etc. The pons literally means ‘bridge’ in Latin and is aptly named as it is a connection between the cerebrum and cerebellum. The cerebrum and cerebellum are parts of the brain that we will get into later. Important nerves such as the ones responsible for feeling in the face, movements involved with chewing, side-to-side movement of the eyes, facial expressions and sound moving from the ear to the brain, originate in the pons. The pons is also associated with the regulation of breath and sleep cycles. The midbrain, which is the top most part of the brainstem, transmits the sensory information to the rest of the brain and the motor information from the brain. The sensory input is also registered by the midbrain, allowing it to alter the movements/actions we make, to better suite the information taken in. The midbrain is like a manufacturer who makes products based on the response of the consumers. It takes down orders and produces the goods, but if the there is a change in consumption, the orders are altered to send out goods that will please the consumers. In a nutshell, the midbrain is responsible for vision, hearing and body movement.

This is just the beginning to understanding the complex organ that is the brain. There are realms of the brain that even neurologists today do not fully understand. There is so much more to discover and hopefully this process can continue until we have a better grasp over why we do what we do. Have you ever ever wondered why you cannot remember what you did when you were a few months old ? Perhaps we will get into that in another essay, but for now use this as a launching pad to traverse through the complexities of the brain. Who knows, maybe you might find that you cannot stop thinking about thinking.