****The pressure exerted by the combined volume of
the 3 intracranial components: Brain tissue/fluids (80-85%), Intracranial blood volume (3-10%), Cerebrospinal fluid (CSF) (8-12%). Normal = 0-15 mmHg. All of these things have to be in balance. Any increase in any one of these components causes a change in the volume of the other (Munro-Kellie hypothesis). Increases in any component may result in: Displacement or shift of CSF, Increasing absorption of CSF, Decreasing cerebral blood volume. Without such changes, intracranial pressure will begin to rise. Normally, minor changes in blood volume and CSF occur with changes in posture, BP, ABG levels, and intrathoracic pressure (coughing, sneezing, straining): **Increased CO2-vasodilation, **Decreased CO2-vasoconstriction.