The main tissue types in the brain are i) gray matter which is composed of the cell bodies of neurons (nerve cells) and other cells which support their structure and metabolism (e.g., glial cells). ii) white matter is made of the extended “wires” that connect neurons to one another over long distances (called axons). Many of these are covered in a fatty substance called myelin which insulates them and allows electrical signals to pass more quickly along the fibres – this is what gives white matter its lighter shade. iii) There are also large fluid filled spaces in the brain called ventricles. The liquid is called cerebrospinal fluid (CSF), it also fills the gaps in the brains wrinkled surface CSF keeps the brain floating so that it is not compressed under its own weight. iv) The brain is a very active organ that uses a great deal of energy – to support this it needs supplies of energy and oxygen which come from its blood supply; there are a lot of blood vessels in the brain including a fine network of tiny capillaries which bring the supplies into close contact with the active nerve cells. v) The brain is surrounded by several layers of membranes which cushion and protect the very delicate soft tissues from damage. The outer membrane is called the “dura mater” roughly translated as “tough mother”.
If you have a strong stomach you might be able to pick out some of these features on an MRI scan of my head which you can see here (warning slightly gruesome).