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23 Cards in this Set

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Autoregulation
mechanism by which blood flow is maintained at a constant rate, despite changes in arterial BP
Blood-brain barrier
mechanism for selective control of movement from blood into internsitital space of brain
Blood-CSF barrier
mechanism for selective control of movement from blood into CSF
brain receives what % of Cardiac Output?
~15% (though it only makes up ~2% body weight)
Average rate of cerebral flow
50ml/100gm/min
Higher in Gray matter (70ml)
Lower in White matter (20ml)
minimum CBF rate for gray matter is approximately:
~15 ml/100g/min

before function begins to suffer
what happens to brain arterioles at low pressures?
these structures dilate, resulting in decreased vascular resistance and maintenance of CBF
what happens to brain arterioles at high pressures?
these structures constrict, increasing resistance and preventing excessive flow
what allows arteriole response to high/low pressure?
thought to occur via myogenic reflex, in arteriolar SM cells
Increased pCO2 causes what changes in cerebral arterioles
VASODILATION
Decreased pCO2 causes what changes in cerebral arterioles
VASOCONSTRICTION
1mmHG change in pCO2 = what change in CBF
2ml/100 gm/min change in CBF
CBF is directly correlated to
metabolic activity, via an undetermined vasoactive metabolite (adenosine, alctic acid, nitric oxide, etc..)
factors potentially affecting regulation of CBF:
sympathetic, neuropeptide, trigeminal, and serotonin inputs, viscosity (may affect CBF/O2 delivery coupling)
factors determining viscosity of blood
HEMATOCRIT
ERYTHROCYTE AGGREGATION
PLASMA PROTEIN CONCENTRATIONS
site of the blood brain barrier
at the brain capillaries, structurally/fxnally different than caps anywhere else in body
how are brain capillaries different than other capillaries?
-tight junction bt cells, no gap junctions or fenestrations
-few pinocytotic vesicles
-large number of mitochondria -astrocytic foot processes
-enzyme systems specific to cerebral vesels
-increased electrical resistance ax membrane
GENERAL permeability factors
Lipid solubility
Smaller Size
Less binding to serum proteins
Less polar
Facilitated Transport systems
are important for what?
have what characteristics?
important for getting insoluble substrates ax
-stereospecific
-have finite capacity
-are subject to competitive inhibition
Transport Systems
Transport System: (Example Substrate)
Hexose: (glucose)
Monocarboxylic Acid: (lactate)
Neutral Amino Acid: (phenylalanine)
Basic Amino Acid: (arginine)
Amine: (Choline)
Nucleoside: (Adenosine)
Purine: (Adenine)
Ion Cotransport Systems
Na+/Cl-
Na+/H+
Na+/K+
ATPase
etc..
CSF is produced by
choroid plexus
Blood-CSF Barrier
CSF is produced by the choroid plexus:
-capillaries have fenestrations
-barrier between the blood and CSF is at the epithelial lining of the choroid plexus
-choroids epithelial cells have tight junctions and few vesicles (like brain capillaries)