The Brain

The human brain, as anyone knows, is an organ the size of a small melon located in the head.

It is protected by the skull can be a series of membranes this sheets of cells between the bone and brain matter, bathed in a liquid called the cerebrospinal fluid (SCF).

This colorless liquid, which consists mainly of water with various proteins, salts and small molecules, fills the ventricles, helps transport material, to the brain and removes debris.

The inward transport actually begins with cerebral blood flow, which carries oxygen from the lungs and nutrients from the food in the stomach to the brain and spinal cord – the central nervous system.

The skull membranes and CSF also hold the brain matter together and provide some cushioning against sudden jolts.

The brain itself is fairly soft, with the consistency of a soft boiled egg.

Since many people have seem animal brains either frozen in butcher’s shops or as anatomical specimens pickled in formaldehyde or preserved in alcohol, there is a general impression that the brain is more solid that it actually is.

The brain has a whitish color, flecked with pink, due to the blood in the small capillaries at its surface.

This external surface, as is seen in so many drawings or models, is deeply furrowed and crisscrossed by an intricate pattern of ridges and valleys, giving it the appearance of a very large walnut.

In monkeys, apes and particularly humans, these convolutions increase the surface of the outer layer of the brain.

This is one of the most important ‘improvements’ in the nervous system brought about by evolution.

The brains of mice and rats have a relatively smooth outer surface, while cats and dogs have some indentations.

But it is only monkeys, and particularly apes, that have convolutions that are almost as complex as those of humans.

The brain of a rat is about the size of an almonds and smooth, an when cortex, the outer layer, is peeled off by careful dissection and flatted, it has an are about the size of a large postage stamp.

On the other hand, why the cortex of the human brain is peeled off and flattened it covers an area about the size of a page of newsprint.

The increase in the area of the cortex or outer layer of the brain has the advantage of increasing the number of cells that can be packed into it, while retaining a sheet-like organization.

If the processing of thins such s vision or memory occurs in the cortex, as we believes it does, this gives a distinct advantage to any organism with many furrows of the surface of the brain, i.e. a relatively large number of cortical cells.
The Brain