Phys - Cerebral Vasculature and Brain Homeostasis Flashcards
three locations of CSF
ventricles
cisterns
subarachnoid space
what are the receptors on the apical membrane of a choroid plexus cell
Na/K ATPase aquaporin channel NKCCl HCO3- channels anion channels
what are the receptors on the basolateral membrane of a choroid plexus cell
Na+ dependent Cl-/HCO3- exchanger (NCBE)
aquaporin channel
describe how sodium travels through a choroid plexus cell and what is its significance
enters cell through NCBE –> actively pumped out via Na/K ATPase
- creates a transmembrane gradient that allows movement of other ions like HCO3- and Cl-
how does HCO3- travel through a choroid plexus cell
HCO3- accumulates intracellularly from continuous hydration of CO2 by carbonic anhydrase –> the gradient drives HCO3- out of the cell into the ventricles down its concentration gradient through anion channel and HCO3- channels
how does Cl- travel through a choroid plexus cell
Cl- accumulates intracellularly from following Na+ into the cell –> creates electrochemical gradient –> leaves cell via NKCCl channel
what drives water from the blood into the ventricles
the osmotic gradient created by movement of Na+, Cl-, and HCO3- drives water in the same direction across apical membrane
how does water travel through choroid plexus cell
aquaporin channels on both basolateral and apical membranes
compare sodium and osmolarity between CSF and serum
about the same levels
compare Cl-, CO2, and pH between CSF and serum
CSF has more Cl- and CO2 than serum and a lower pH (7.33)
compare protein, glucose, K+, Ca2+, Mg2+, and HCO3- between CSF and serum
serum has more protein, glucose, K+, Ca2+, Mg2+, and HCO3- than CSF
if intracranial pressure is less than 68 mm CSF, how does this affect absorption
no absorption occurs if ICP is less than 68 mm CSF
normal is 112
how does carbon dioxide regulate cerebral blood flow
carbon dioxide will dissociate into carbonic acid, which which then dissociate into hydrogen, which causes vasodilation of blood vessels increasing blood flow
how does oxygen regulate cerebral blood flow
sensing of decreased oxygen causes vasodilation to increase blood flow
how do astrocytes regulate cerebral blood flow
the metabolites they release have vasodilator activities which increases blood flow
how does metabolic activity in the brain regulate cerebral blood flow
metabolic activity increase blood flow to the area of the brain that is functioning for that activity
when systemic cardiac output increases, what autonomic system turns on in the brain
sympathetics turn on to vasoconstrict
when systemic cardiac output decreases, what autonomic system turns on in the brain
parasympathetics turn on to vasodilate
what NT and receptors are used by sympathetics in the brain
NE and NPY
alpha-adrenergic receptors
what NT are used by parasympathetics in the brain
Ach, VIP, NO
what NT are used in sensory innervation to the blood vessels of the brain
SP, NKA, CGRP
why does decreased CSF cause pain
- what does the brain do to stop the pain
it renders the brain heavier, so simple motion torques the blood vessels which causes pain
- sensory afferents activate vasodilation to increase blood flow and CSF volume
how are ICP and cerebral blood flow related
as ICP increases, cerebral blood flow greatly decreases
how are PaCO2 and cerebral blood flow related
as PaCO2 increases, cerebral blood flow increases
how are PaO2 and cerebral blood flow related
- if O2 is too low, cerebral blood flow increases
- as O2 increases cerebral blood flow remains the same
- if O2 gets too high, cerebral blood flow decreases
how are cerebral perfusion pressure and blood flow related
- when cerebral perfusion pressure is low, cerebral blood flow is low
- cerebral perfusion pressure increases without change in cerebral blood flow (plateaus)
- if cerebral perfusion pressure gets too high, cerebral blood flow also begins to increase again
autoregulation of cerebral blood flow in times of increasing blood pressure is mediated by _____
sympathetic stimulation
what is the process that occurs in the event of decreased brain perfusion
activation of vasomotor centers that monitor perfusion at all times –> increase systemic blood pressure –> drives blood to the brain
what is the effect of anemia on cerebral blood flow
increases it
what is the effect of polycythemia on cerebral blood flow
decreases it
how does alkalosis affect cerebral blood flow
decreases it
how does acidosis affect cerebral blood flow
increases it
what are the BBB and blood-CSF barrier highly permeable to
water
CO2
O2
lipid soluble substances
what are the BBB and blood-CSF barrier slightly permeable to
Na+
Cl-
K+
what are the BBB and blood-CSF barrier nearly impermeable to
plasma proteins and non-lipid-soluble organic molecules
function of pericytes in the BBB
contractile cells that control what gets into the BBB
how does H2O, CO2, and O2 cross the BBB
passive diffusion
how do unbound steroid hormones and lipid soluble substances cross the BBB
passive diffusion
how does glucose cross the BBB
GLUT1
is GLUT1 dependent on insulin
no (it is non insulin dependent)
expression of the NaK2CL is tied to what protein
endothelin 1 and 3
endothelin production in the BBB is tied to what signals
astrocyte signals
function of P-glucoprotein in the BBB
moves drugs that don’t belong that crossed the BBB back into the blood
where is the GLUT3 transporter expressed
neurons
where is the GLUT5 transporter expressed
microglia
where is the 45 kD isoform of GLUT1 expressed
astrocytes
where is the 55 kD isoform of GLUT1 expressed
microvessels
choroid plexus
ependymal cells
primary function of posterior pituitary as a circumventricular organ
secretory
primary function of area postrema as a circumventricular organ
sensory; initiation of vomiting in response to chemotactic triggers
primary function of organum vasculosum of the lamina terminalis (OVLT) as a circumventricular organ
sensory; regulation of total body water and thirst - target of angiotensin II
primary function of subfornical organ as a circumventricular organ
sensory
