PHGY 350 Lecture Notes - Lecture 11: Middle Cerebral Artery, Brain Ischemia, Optic Chiasm
28 Nov 2016
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Brain (demanding organ) require constant supply of o2 & glucose (can"t use other energy source). *no innervation of blood vessels so depends on immediate local factors: local co2, ph, bp. (brain adjust to w/e is flowing in surrounding. Can"t shunt from one part to another like lung). 2 main source: internal carotid arteries, vertebral arteries. But have a detour if the 2 fails: circle of willis. Anastomoses (connection between one artery to the next) provide alternate pathways. General pattern of brain: anterior arteries supply frontal lobe; middle cerebral artery supplies temporal, parietal lobe; vertebral artery for occipital or anastomoses from the other direction. Blood brain barrier (nourish and protect at level of capillary) Protective mech by impermeable capillaries tightly joined w/ tight junction (not pores). Limits passage of damaging materials into brain & controls delicate but essential balance of electrolytes, glucose, proteins in brain. Tight endothelial junctions (tighter than rest of body).
