Apart from the meninges which amount to very little, the main parts inside your head include the brain, the blood supply to and from this, and the cerebrospinal fluid (CSF) that surrounds all the structures.
Any change to one of the three groups has a direct impact on the other two. The space inside the skull is limited and a tight balance is maintained in healthy heads. This is known as the Monro-Kellie doctrine (Edinburgh anatomists).
We can measure the intracranial pressure (ICP) which normally sits around 7-15 cmH20 in resting adults - either through lumbar punctures or by direct ports ("bolts") into the ventricles.
Presentation
Head injury in motor vehicle collision (MVC). Reduced level of consciousness.