goodduck

[ concept ]
1.   CPP = MAP - ICP, ie : "effective perfusion pressure"
2. " autoregulation "-> maintain cerebral blood "flow"
3.   factors affect CBF(according to loaction) 
      a. extracranial ->  MAP, viscosity of blood
      b. perenchyma-> arteriole vasoconstriction/dilation, ICP
      c. extracranial ->  MVP
4.  "any" change in MVP "promptly" causes similar change in ICP
5.  CBF increase -> ICP increase

[examples]
1. MAP increase -> CPP increase -> arteriole in brain vasodilaton -> CBF relative constant 
2. MAP decrease -> CPP decrease -> arteriole in brain vasoconstriction -> CBF relative constant
3. venous pressure increase ->a. decrease effective perfusion pressure(CPP decrease)  -> CBF decrease
                                                         b. "promptly" ICP increase -> compress cerebral vessel
[practical use]
1. Cushing reflex
2. negative g -> MAP/MVP increase -> both P arteriole /  ICP increase -> vessel not rupture
3. positive g -> MAP/MVP decrease -> both P arteriole / ICP decrease -> vessel not collapse