Unit 5: The nervous and endocrine systems                    1   2   3   4   5

3. The central nervous system

It is formed by the nerve centers: the encephalon (brain) and the spinal cord.

These organs are protected by bones:

-  Cranium (skull) that covers the encephalon.

-  Vertebral column that covers the spinal cord.

In addition, there are three membranes that are located underneath the bone and that envelop these nerve centers, the meninges. They are from outside to inside: dura mater, arachnoid mater and pia mater.

Between the meninges and the central nervous system is a fluid called the cerebrospinal fluid. This fluid acts as mechanical and immunological protection and provides nourishment to the nerve tissue.

In the organs that forms the central nervous system is possible to differentiate two zones:

-  Grey matter, formed by somas and dendrites.

-  White matter, formed by axons. 

3.1. Why is the colour of grey and white substances different?

3.2. What are the protective structures of the nerve centres?