Four thousand years ago in Ancient Egypt, if you were of higher status and died, you would have ended up getting mummified. The Ancient Egyptians believed that if your body was preserved after death in this world, then a comfortable life in the afterlife would be assured for your soul.

There was a special process that was applied when mummifying a body. The body was embalmed in chemicals and then wrapped up in several layers of cloth. However before the wrapping, the internal organs were taken out and put in jars.

The stomach, the liver, the lungs, and the intestines were all removed and placed in canopic jars made of either wood, stone or porcelain and sometimes topped with the head of a god. The heart stayed in, because the Egyptians believed that it would be weighted (and thereby judged) against the feather of the goddess of truth, morality and justice, Maat.

To remove the brain, a long, sharp object was first put through the nostril. It would break through into the brain and then liquefy it. The liquefied brain would then ooze out through the nostril. What would they do with it?

Once it came out, they would collect it and… throw it away! The Ancient Egyptians did this because they believed that it was of no importance for the human being. For them, it was the heart that was the center of all action.

For the Ancients, the brain just seemed to be some sort of a squishy substance with no real purpose, apart from filling up the head.
That view began to change when Galen (remember the former physician of the gladiators?), one of the most well-known doctors of Antiquity, did a demonstration where he silenced a squealing pig by isolating a nerve that tied the larynx to the brain. In this way he proved that the brain was the organ controlling the actions of living things.

Galen was not the first ancient to speculate on the nature of the brain and its role in the body (for example Hippocrates did too), but he was the first one that we know of that traced out the different nerves and muscles and connected them to the brain, and also who gave practical proofs (such as the pig experiment) of how this works.

However, among many people this view still didn’t catch on and most still kept on considering the heart as the primary seat of human actions until the Renaissance proved once and for all the central role of the brain in the body.

The role of the brain

The brain is the primary organ in the nervous system and controls the behavior of living beings. It is the most complex organ in the body. The basic structure of the human brain bears many similarities to that of other animals, but there are also some important differences. These differences are what give humans the power to reason.

There are numerous basic roles that the brain performs in the body:

  • handles all your physical movement (balance, walking, standing)
  • regulates internal processes (such as breathing, body temperature)
  • controls your actions (whether through instinct or reason)

This happens when signals from the outside (collected through sight, smell, touch, taste, hearing) are passed into the brain, which then interprets them and acts based on this interpretation. Most of this happens subconsciously.

For example this is how the signals that are captured by your hearing are transported to and then interpreted by the brain:


How does the brain perform its functions?

The brain sits at the top of a huge communications system inside your body called the nervous system. Through the nervous system, signals from one part of the body are transmitted to other parts of the body, which allows your body to function.

The nervous system is divided into two parts, the central nervous system (CNS) which consists of the brain and spinal cord, and the peripheral nervous system (PNS), which is the huge network of nerves running all through your body.

What happens is that some sort of a signal comes in from the outside and is relayed through the nerves in the PNS and all the way to the brain, which then interprets them and determines what to do about them. The command from the brain then gets passed back through the PNS and your body reacts accordingly.

For example if you touch a hot stove with your fingers, that produces a signal in your fingertips, which then gets passed through the different nerves all the way to the brain. The brain interprets this as dangerous since the heat could damage your body, and then tells your hand to retract itself from the stove. This command gets passed down through the nerve network and into the muscles, which then contract and pull the hand away from the stove.

Mr. Brainiac: “Don’t touch that stove!

Smart Chimp, not listening to Mr. Brainiac, moves in closer and puts his hand on the stove: “Ouchhh!

Smart Chimp’s hand immediately retracts.


Mr. Brainiac shakes his head: “I told you so. Luckily your brain is still at least half-functioning, otherwise you could have been in big trouble.

Smart Chimp: “That hurt!

Mr. Brainiac: “Of course it did! You are not meant to touch hot objects, since they could cause irrepairable damage to your body. That’s why your body reacts the way it does. You start doing something stupid like touching a stove and immediately little signals pass through your body into the brain, which interprets it as dangerous and stupid and commands your hand to stop touching the stove. At least your subconscious brain is smarter than your conscious brain.

Smart Chimp: “Shut up Mr. Brainiac!

All this is possible through the way that the entire network of message-passing is set up. At the basis of all of this are small cells called neurons.

Deep down, neurons are cells just like any other cell in your body, but they do have one key ability that separates them from the rest. They can pass on electrochemical signals (more detailed explanation how that works is here).

These electrochemical signals are the ones that pass information and commands through the body and the brain and without them, you would not be able to function. These signals travel from one neuron to the next through jumping over the synapses that are between them.

Synapses are a very important concept to keep in mind. They are basically small gaps between the different neurons and nerve signals pass from one neuron to the next by triggering the release of neurotransmitters.

This is how it’s done:

Once a nerve impulse has triggered the release of neurotransmitters, these chemical messengers cross the tiny synaptic gap and taken up by specialized receptors on the surface of the next cell. These receptors act much like a lock and the neurotransmitters function much like a key. This process then converts the chemical signal back into an electrical signal.

This basic signal-passing mechanism is what is behind all the actions of your body. Without neurons and all the processes associated with them, you would not be able to do anything.

Mr. Brainiac: “So you see Mr. Chimp, without neurons you would not be able to scratch your head, swing through trees or do anything.

Smart Chimps gets closer to Mr. Brainiac, slaps him and immediately jumps far back.

Smart Chimp: “You won’t be able to do anything about me slapping you, even with all your neurons!


There are different types of neurons:

1) Sensory neurons – which transmit sensory information (collected by the five senses) to the brain
2) Motor neurons – which transmit commands from the brain to the spinal cord and then the muscles
3) Interneurons – which interconnect different neurons in the brain and the spinal cord

Neurons are located in different parts of your body, but they are very densely spread in the brain.

Your brain is made up of over 100 billion neurons, which are supported in their work by glial cells (which are actually much more numerous than neurons in the brain). These are the basic building blocks of all the larger structures of the brain.

Parts of the brain

The brain is the command organ of your body. It is divided into several parts, all of which have different roles to play. To help you get a better picture of how it works and which parts of it control which processes, we can use what is called the triune model of the brain. This is a concept that was proposed by neuroscientist Paul D. MacLean and described in his book “The Triune Brain in Evolution”.

If you look at the human brain, you can pretty much determine how it evolved if you compare it to the brains of other animals. For example, lizards only have some of the lower structures of the brain, while mammal brains already include most of the structures that humans have.

This sort of evolution is even more evident if you look at the development of the brains of human babies in their mother’s womb. Each human baby passes through a fish phase, a reptile phase, a lower mammal phase, until it develops a brain which has all the basic features of a human brain.

Noticing these patterns, MacLean divided the brain into 3 parts:

1) The Reptilian Brain – consists of the basal ganglia, the brain stem and the cerebellum and takes care of the most basic bodily functions (heartbeat, breathing, as well as balance and the use of muscles) and instincts (such as fight or flight, reproduction, status drive, aggression, dominance).

2) The Paleomammalian Brain – consists of the limbic system and it is basically the seat of emotions (as well as different types of memory).

3) The Neomammalian Brain – consists of the cerebrum and is the seat of many of the higher functions such as reasoning (and things like logic, planning, language).

Of course these titles are just a handy metaphor and things are much more complex than that (especially as newer research keeps on discovering new things). For example, while in the model the Paleomammalian Brain (more particularly the limbic system) is where the parental instinct arises from, modern research has shown that this instinct is already present in some species of reptiles and even fish. So these categories are not really fixed.

While not being 100% true, this model has captured the popular imagination. You might have seen terms like “the reptilian brain” be thrown around in several popular books on psychology and so in order to better illustrate how the brain works and which parts of it are responsible for what, I will keep an adjusted version of these categories.

In fact, I will use a quadrune model of the brain! ๐Ÿ™‚

This is a concept that evolutionary theologist (yes there seems to be such a thing!) Michael Dowd uses to explain how the brain works. Basically, he divides it up into the Lizard Mind, the Lil’ Furry Mammal Mind, the Monkey Mind, and the Higher Porpoise.

The first two categories are the same as the ones in the triune model, but Dowd further divides up the neocortex into a Monkey Mind (since monkeys have much of the same higher functions as humans) and a part which is only present in humans, which he calls the Higher Porpoise (as in dolphins and whales), which is the prefrontal cortex or advanced brain.

Basically, humans have a much bigger and more developed brain than even our chimpanzee cousins. The reason for this might be culture!

The development of culture might have stimulated the development of a larger brain (or vice versa? ๐Ÿ™‚ ). While chimps (and some other animals, including a few species of birds) do have various levels of primitive culture, human culture is much more complex and has a much bigger influence on the brain.

Based on all this, let me introduce to you my own model of the brain. It is divided into four parts: the lizard brain, the dog brain, the chimp brain, and the human brain!

Don’t get the chimp brain in my model confused with the chimp brain from the book “The Chimp Paradox” by Steve Peters. In that book, it refers to the limbic system, while in my model it covers most of the cerebrum.


I was gonna do a section titled “your lobster brain”, but that’s basically just the nervous system plus some ganglia at the top. However, if you want, you can go back and retitle the section where I talk about the nervous system as: Your Lobster Brain.

Me: “Happy, Mr. Lobster?

Lobster Brainiac: “Yeah better, but next time make more of an effort.

Me: “Don’t worry. The fish and amphibians got snubbed too.

Remember that this model is not scientific, but more of a metaphor to demonstrate in which parts of the brain the different functions reside. It could be used as a mnemonic device: ah emotions, dog brain, limbic system!

Let’s get to describing the different parts of the brain!


The Lizard Brain

Have you ever seen a lizard go about its business? They crawl, they eat, once in a while they mate. Nothing complicated, their behavior is primarily driven by instinct.

An instinct is an innate and automatic drive that pulls an animal towards a certain behavior. There are different stimuli that can trigger an instinctual behavior and most of this happens on the deepest subconscious level.

In humans, it can be overridden to a certain extent, but in most animals instinct is the main reason of why they do what they do. Its main aim is to allow the animal to survive and reproduce (spread your genes).

The parts of the brain that govern instincts developed early in the evolutionary process and so many different types of animals share them. They are involved in such primary instinctual processes, as fight or flight, sex, status drive, dominance, aggression.

These parts of the brain also control the different subconscious processes that keep your body functioning such as heart beat, body temperature, breathing, or balance.

The main parts of this section of the brain are the brain stem, the cerebellum and the thalamus.

Brain Stem

The brain stem is made up of three major parts: the medulla oblangata, the pons, and the midbrain.


The brain stem plays a very important role in your body. Being connected to the spinal cord, all the signals going to and from the brain pass through it.

It is also the part of the brain that subconsciously controls many of the basic functions of the body. In that way, it is fundamental for keeping you alive.

Medulla Oblangata

Even if you are lying still, there are some basic bodily processes that need to be going on if you want to stay alive. The medulla oblangata is the lowest part of the brain, the one that connects to the spinal cord, and also the part which regulates these basic functions.

If you are breathing, your heart is pumping, and your blood is circulating (blood pressure), then this is thanks to your medulla oblangata doing its job.

Another important role performed by the medulla and one that comes in handy especially if you have been out all night and drinking a bit too much alcohol, or if you ate something that didn’t sit well in your stomach, is vomiting. Yes, if you are bent over the toilet, feeling nauseous and about to empty out the contents of your stomach through your mouth, that’s your medulla doing a good job!


Let’s imagine you go out on the town and you start drinking copious amounts of alcohol. Beer…give it to me! Vodka… let’s do shots! Tequila? Why not!

After a while, you start realizing that might not have been such a good idea. You start seeing double, tripping over yourself, and have to go the bathroom every two minutes. You might have a problem!

Right above the medulla, you have the pons and it is involved with all the stuff described before. If you have been drinking and cannot keep your balance, the pons is involved there. Among its many roles, it helps your keep its balance (together with the cerebellum). If you want to take a piss on the way from the bar, the pons is also responsible, as it play a role in bladder control.

The pons is also involved in many other activities. One of its roles is to help the medulla regulate your breathing by controlling the amount of air you take in. Other things it helps regulate are sleep, and some of the senses like hearing, vision, and taste.


You just did your favorite activity like having sex or posting weird statuses on facebook. You got 33 “Likes” on them! You feel good. That’s because your brain releases a chemical called dopamine.

Dopamine is sometimes called “the pleasure molecule” and it is produced in an area of the midbrain called the substantia nigra, literally “the black substance” (that area is actually black in color).

The midbrain is also involved in such things as movement (often referred to with a fancy phrase “motor control”), as well as vision, hearing, sleep, and temperature control.

Basically what it helps do, is integrate the inputs coming in from the outside (such as from your eyes), interpret them, and then based on this interpretation give command to the muscles to perform a certain action.

One interesting thing it is involved in is called proprioception. Look down at your hands. Do you “feel” them? Now look at your surroundings. Can you locate yourself? Are you upside down?

Proprioception is your body’s awareness in space and helps you get a sense of where you are located and how you are moving. Together with the basal ganglia and the cerebellum, the midbrain is one of the key players in helping you be aware of your sense of proprioception.

Dr. Brainiac looking worried: “Mr. Chimp, what is the problem?

Smart Chimp barely standing and bouncing from side to side: “It was two for one shots night over at El Cheapo Pub.

Smart Chimp then quickly, but clumsily climbs up the nearest tree and hangs himself upside down from one of its branches: “Wow, my head is spinning…

Dr. Brainiac: “That’s because you are hanging upside down and you are drunk.

Smart Chimp vomits.



The big ball in the back of your brain is called the cerebellum. It plays a major role in controlling your movement. While most of the commands for movement originate in other parts of the brain, many of them pass through the cerebellum, which then modifies them and makes them more precise.


If you want to do any type of activity which involves movement (could be running, jumping or even cutting meat with a knife), the cerebellum is the part of the brain that is heavily involved.

It helps with the maintenance of correct posture, as well as balance. One of the things that it does is coordinate all the different movements together. This then not only makes your body move smoothly, but also helps you learn different skills such as kicking a soccer ball or doing a back flip.


The thalamus is located towards the middle part of your brain and serves one very important role: it routes all the different signals coming from the senses to the correct parts of the brain and then also directs the responses and commands back to where they are supposed to go.


So its main function is to serve as sort of a router for your brain. Since most of the different signals going through the brain pass through it, the thalamus is very important in regulating consciousness, as well as such things as when you sleep and when you are awake.

The Dog Brain

If you are a dog owner, then you probably know that dogs are very emotional creatures. They get excited often, especially when it comes to food and being scratched.

The limbic system is the seat of emotions in the brain and that’s why I describe it as the “dog brain”. Dogs are guided by their feelings. Their main concerns are about the basics: where to get food and whose leg they should hump.

The concept of feeling an emotion is very important in order to understand how living things function. An emotion can be defined as:

1) an affective state of consciousness in which joy, sorrow, fear, hate, or the like, is experienced, as distinguished from cognitive and volitional states of consciousness.
2) any of the feelings of joy, sorrow, fear, hate, love, etc.
3) any strong agitation of the feelings actuated by experiencing love, hate, fear, etc., and usually accompanied by certain physiological changes, as increased heartbeat or respiration, and often overt manifestation, as crying or shaking.

Emotions have a strong pull on your behavior. They evolved as a way to guide you quickly in different situations. When you feel fear, you know that you should be on the lookout, when you feel hunger, you know that you should eat, when you feel joy, you are rewarded.

This is System 1 as Kahneman describes it. It lets you react quickly based on outside stimuli.

Limbic System

The limbic system sits in the middle of the brain, on both sides of the thalamus and is primarily responsible for emotions, as well as for the formation of memories. It includes several different parts that are crucial for you feeling emotions:



Your body temperature is too high? You got a problem. Your electrolyte level is too low? You got a problem. Your blood pressure is too low? Houston, we have a problem.


The part of the brain that deals with these types of problems is the hypothalamus. Its main role is to maintain internal body balance, homeostasis. Things like blood pressure, body temperature, or body weight, all have their ideal point. When that function is nowhere near that ideal point, the hypothalamus gets to work in order to get back to it.

The hypothalamus releases hormones that control the production of other hormones. These then regulate things like sleep, hunger, thirst, even sex drive. It even controls certain aspects of parenting behavior.

It is also very important if you want to get big, since it releases a hormone which controls the production of the growth hormone in your body.


Imagine yourself walking in dangerous territory, in the dark, with a saber-toothed tiger in the area. Your heart starts pounding and you start sweating. You feel anxious, but continue on walking slowly, taking a look behind your back at every step.

That is your amygdala at work. The amygdalae are actually two separate almond-shaped balls located away from each other and playing a huge role in the processing of emotions.


Most of the brain’s circuits that warn of any type of danger are located in the amygdala. Stimuli from the outside are processed by it and if they appear dangerous, special signals are sent out. So the emotion of fear comes from there.

Also imagine that another day you are walking through a little path, in a stretch of land where a few weeks ago you were attacked by a cave lion. It’s the middle of the day and there is nothing there, but you feel anxiety and fear.

That is your amygdala at work again. It is involved in episodic memory, that is the storage of memory together with the different feelings and emotions associated with it. So that’s why you might have negative feelings associated with something (and therefore mental barriers) that no longer poses any threat.

Dr. Brainiac comes up unexpectedly behind Smart Chimp. The Chimp feels a strong chill go up his back and stomach, and immediately jumps up and scuddles up the nearest tree.

Smart Chimp: “You startled me!

Dr. Brainiac: “I am sorry! Didn’t mean too.

Smart Chimp: “Yeah! Next time I could go chimp-style on your face!

Dr. Brainiac: “Please don’t.

Smart Chimp: “Watch yourself. This place gives me the creeps. I don’t know why.

Dr. Brainiac: “Maybe since a bunch of coconuts fell on you here one day last year, from that exact palm tree above you.

Smart Chimp: “Oh yeah coconuts. They are a silent killer!

The amygdala is involved in emotions, especially the body’s fear mechanism, decision-making, as well as memory. There are some differences between men and women. For example the result of one study shows that women have stronger memories for emotional events.


Do you remember what you had for lunch today? You probably do, and that’s because your hippocampus is working properly. The hippocampus is actually divided into two objects, each one on one side of the brain.


One of the roles that it plays in the brain is the storage of short-term memory as long-term memory. This means you can remember things that happened to you not that long ago. People who have damage in this area cannot remember what they did even a few minutes ago.

Your short-term memory stores information about an event temporarily in the pre-frontal lobe and then passes it through the hippocampus which sorts it and then sends it for long-term storage. Through this entire process it also helps you create associations between different ideas and objects and thereby you can remember them better.

It helps you to memorize facts:

When we remember new facts by repeating them or by employing various mnemonic devices, we are actually passing them through the hippocampus several times. The hippocampus keeps strengthening the associations among these new elements until, after a while, it no longer needs to do so. The cortex will have learned to associate these various properties itself to reconstruct what we call a memory.

The hippocampus also helps you remember where things are located, as well as the identities of living things. You wouldn’t be able to get to work each day, if it wasn’t working properly!

The hippocampus is also one part of the brain that has been shown to grow with use. One group of people who grow it through years of use are taxi drivers! They have to memorize thousands of locations and streets and so over time, it gets larger in order to encompass all these memories.

Pituitary Gland

This is a small gland that hangs off the hypothalamus and produces several hormones important for the human body, such as the growth hormone, thyroid stimulating hormone, puberty hormone, and prolactin.

It also controls other hormone-producing glands in the body. For example through its release of the ACTH hormone, it stimulates the release of cortisol during times of high stress.

Basal Ganglia

So did you tie your shoes today? If you did, then you executed a skills pattern, something that the basal ganglia is in charge of.

Skills patterns involve things that you initially have to learn, but once you learn them require very little effort to execute. Many of them become automatic and get executed without much thinking on your part.

The basal ganglia plays an important role in motivation and action selection. It helps in deciding which of several courses of action to select. This is tied in with motivation. If a certain action works, then the basal ganglia helps to learn it and it is put to memory and used whenever needed.

So the basal ganglia promotes the use and reuse of best practices for different courses of action. There are three things at play here doing an action, getting a reward for it, and then this process becoming automatic. The release of dopamine is what creates this reward effect, which then reinforces the action.

According to scientific studies, the basal ganglia is very important for habit formation. This it does in conjunction with the cortex.

Dr. Brainiac: “Do you remember what you did yesterday?

Smart Chimp: “No, I might have been drunk.

Dr. Brainiac: “Maybe you damaged your hippocampus?

Smart Chimp raising his eyebrow: “You want to see damage?

Dr. Brainiac: “What type of damage?

Smart Chimp swinging his arms wildly: “My arms in your face! I have been practicing fighting for so long that hits have become automatic!

This is getting a bit too long. However if you read up to here, I have exciting news! In the next part, we will look at the chimp and human parts of your brain!

Read More:
How to be a critical thinker and develop your mental powers

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