HSC 350 Lecture Notes - Lecture 1: Dural Venous Sinuses, Superior Sagittal Sinus, Choroid Plexus
Document Summary
Human brain has high metabolic rate & oxygen requirements = Only 2% of total body wieght but receives ~ 15% cardiac output & consumes 20% of the oxygen used by the whole body. Cerebral blood flow (cbf) == 750 1000 ml/min. Arterioles constrict when systemic blood pressure is raised and dilate when it is lowered. Regional cerebral bloodflow must meet the demand of rapidly changing oxygen & glucose metabolism & byproducts (co2 lowered ph, k+, adenosine) that accompany normal brain activity ----functional hyperemia (is the basis for modern imaging techniques) Blood flow follows changes in brain cellular activity. frmi is measuring just the blood flow but not oxygen utilization. The result is an increase in the local oxygen availability because the increased supply of oxygen by flowing blood exceeds the increased local demand for oxygen. fmri based on the bold effect blood oxygen level (dependent signal).
