Evoltionary Brain Development

           The Evolution of the Nervous System

All animals can respond to changes in their environment. Even single celled organisms are able to survive and perform life tasks by using a ‘resting membrane potential’.

The first neurons were developed in multicellular animals such as jellyfish. They have developed a neural net with sensory and motor neurons. They do not have a centralized centre for neurons or an integrating centre.

In flatworms, there is a developed central region at the head where the neurons have clustered, showing evolution towards one end.

The next development is seen in the earthworm where the neurons have formed many clusters along the body. They are known as ‘ganglia.’

Then, fish evolved a very small forebrain while the rest of the brain is much larger. The next evolution is seen in goose which have a larger forebrain and other specialized areas of the brain.

Humans have the largest forebrain compared to any animal which is what has given rise to our conscious thoughts and ability to think abstractly.

Reference:
Silverthorn, Dee Unglaub. 2007. Human physiology: an integrated approach. San Francisco: Pearson/Benjamin Cummings.