Trans - Blood Brain Barrier Flashcards
perivascular sheath of pia mater around brain capillaries
Virchow-Robin space
intracranial veins drain into :
dural sinuses
contributes to 40% of total vascular resistance in CNS
penetrating parenchymal arteries
difference of capillaries inside and outside CNS
outside - may be fenestrated
inside - basement membrane invested by nearly continuous layer of foot processes (astrocyte extensions)
BBB - function
prevent/control entry of substance into CNS
transport system in BBB
facilitated diffusion
what type of substances can pass through BBB
lipid-soluble
what junctions are in BBB
tight junctions
how do substances pass through the BBB
substances cannot pass through intracellular spaces - they need to pass through the plasma membrane of the endothelial cells by facilitated diffusion
transport of glucose into CNS
through GLUT1
[T/F] astrocytic foot processes are important components of BBB
F
[T/F] BBB fully encloses all structures in the brain
F
why is the BBB less developed in some areas of the brain
to allow the brain to monitor blood content/flow
where is the BBB less developed?
- anterior 3rd ventricle
- tuber cenereum (hypothalamus)
- pineal gland
- area postrema (in 4th ventricle near obex)
brain is __% of body weight
2
brain uses up ___% of cardiac output
15
normal blood flow through brain
50-55 ml/100g/min
~750 ml/ min
brain uses up ___% of O2
20
normal O2 consumption
3.7ml/100g/min
~50ml/min
relationship of perfusion pressure and cerebral blood flow
direct
relationship of total vascular resistance and cerebral blood flow
inverse
principal extracerebral factor affecting CBF
systemic arterial BP
normal cerebral venous pressure is relatively ____
low
CBF is (1)__________ by up to (2) _____ in anemia
- increased
2. 30%
CBF is (1)___ by up to (2)___ in polycythemia
- decreased
2. 50%
resistance to flow is (1)_____ by arterial disease, causing (2)_______ of CBF
- increased
2. decrease
resistance to flow is (1)_____ by pathologic anastomosis, causing (2)_______ of CBF
- decreased
2. increase
least significant mechanism of regulating intracranial pressure
neurogenic
extrinsic neurogenic signals for regulating intracranial pressure
- parasympathetic
- sympathetic
- trigeminal nerve
intrinsic neurogenic signals for regulating intracranial pressure
locus ceruleus
fastest responding mechanism for regulating intracranial pressure
myogenic
most potent mechanism for regulating intracranial pressure
pCO2
mechanisms by which CO2 and O2 may act in response to pressure changes
- direct to muscle –> ex. supply of oxygen causes vasoconstriction
- indirect –> stimulation of neurogenic detector mechanisms for gas concentration or pH
acidosis will cause:
vasodilation
alkalosis will cause:
vasoconstriction
myogenic response to increased pressure? why?
vasoconstriction –> to prevent too much blood going into the brain
myogenic response to decreased pressure? why?
vasodilation –> to allow more blood to perfuse brain despite low arterial pressure
increased pCO2 causes what? why?
vasodilation –> increased carbon dioxide means increased metabolism. vasodilation to allow fresh blood to perfuse the tissue and carry away waste products
decreased pCO2 causes what? why?
vasoconstriction –> no need to increase flow to cope with increase in metabolic byproducts
decreased pO2 causes what? why?
vasodilation –> need to increase flow to perfuse the tissue
increased pO2 causs what? why?
vasconstriction –> no need for increase in flow, tissue is not hypoxic
consequences of high intracranial pressure
squeezing of brain tissue –> brain damage due to mechanical injury
consequences of low intracranial pressure
brain damage due to hypoperfusion
ability of an organ to maintain its internal blood flow constant for all by the widest extremes of pressure
autoregulation
in what BP range does CBF autoregulation occur
60-150 mmHg arterial BP
what is the maximum BP for autoregulation of CBF
160mmHg
main mechanism for autoregulation in CBF
myogenic
mechanism of neurogenic autoregulation of CBF
influence through neurotransmitters
strongest mechanism for autoregulation ifn CBF
chemical-metabolic
chemical-metabolic autoregulation of CBF involves what:
CO2, O2, pH
transient increase of CBF in regions of the brain active in certain thoughts or emotions
metabolic coupling of CBF
duration of metabolic coupling of CBF
1-2 seconds
overall effect of metabolic coupling of CBF on total CBF
minimal/negligible