How is a healthy brain different from an injured brain?

Normally, the healthy brain is enclosed inside of a skull, which serves as a protective shield for the fragile brain. The brain is composed of nerve cells or neurons that form tracts that route all over the brain. The neurons transport vital messages to parts of the brain. The brain then uses this information to execute important functions such as breathing, heart rate, body temperature, body movements, personality and the senses (vision, hearing, taste, smell, and touch).