THE BRAIN

How the Human Brain evolved?

The human brain evolved in three main stages . Its ancient and primitive part is the innermost core reptilian brain.

Next evolved the mammalian brain by adding new functions and new ways of controlling the body. Then evolved the third part of the brain, the neocortex, the grey matter, the bulk of the brain in two symmetrical hemispheres, separate but communicating. To a considerable extent it is our neocortex which enables us to behave like human beings.

So the human brain consists of these three different but interconnected brains and the way in which these three brains interact with each other underlies human behaviour.

Reptilian Brain

Innermost in our brain is what is called the reptilian brain, its oldest and most primitive part. The reptilian brain appears to be largely unchanged by evolution and we share it with all other animals which have a backbone.

This reptilian brain controls body functions required for sustaining life such as breathing and body temperature. Reptiles are cold-blooded animals which are warmed by the daylight sun and conserve energy by restricting activities when it is dark.

 

Mammalian Brain

Next to evolve from the reptilian brain was the mammalian brain. An enormous change took place as mammals evolved from reptiles, the mammalian brain containing organs:

1. For the automatic control of body functions such as digestion, the fluid balance, body temperature and blood pressure (autonomic nervous system, hypothalamus).

2. For filing new experiences as they happen and so creating a store of experience-based memories (hippocampus).

3. For experience-based recognition of danger and for responding to this according to past experience. And for some conscious feelings about events (amygdala).

Human Brain

And the mammalian brain became the human brain by adding the massive grey matter (neocortex) which envelopes most of the earlier brain and amounts to about 85 per cent of the human brain mass.

This massive addition consists mostly of two hemispheres which are covered by an outer layer and interconnected by a string of nerve fibres.

The brain is actually divided into its ‘hemispheres’ by a prominent groove. At the base of this groove lies the thick bundle of nerve fibres which enable these two halves of the brain to communicate with each other.

Brain Waves

The brain functions by sending electrical signals from one place to another. Very small charges pass between nerve cells, accompanied by changes in electrical potential, in voltage.

 

 

Mammalian Brain

Next to evolve from the reptilian brain was the mammalian brain. An enormous change took place as mammals evolved from reptiles, the mammalian brain containing organs:

1. For the automatic control of body functions such as digestion, the fluid balance, body temperature and blood pressure (autonomic nervous system, hypothalamus).

2. For filing new experiences as they happen and so creating a store of experience-based memories (hippocampus).

3. For experience-based recognition of danger and for responding to this according to past experience. And for some conscious feelings about events (amygdala).

Human Brain

And the mammalian brain became the human brain by adding the massive grey matter (neocortex) which envelopes most of the earlier brain and amounts to about 85 per cent of the human brain mass.

This massive addition consists mostly of two hemispheres which are covered by an outer layer and interconnected by a string of nerve fibres.

The brain is actually divided into its ‘hemispheres’ by a prominent groove. At the base of this groove lies the thick bundle of nerve fibres which enable these two halves of the brain to communicate with each other.

Brain Waves

The brain functions by sending electrical signals from one place to another. Very small charges pass between nerve cells, accompanied by changes in electrical potential, in voltage.