Cerebral vasculature and brain homeostasis Flashcards
what is the direction of water flow across a choroid plexus cell?
blood => ventricular lumen
what creates the osmotic gradient carrying water from the blood to the ventricular lumen?
Na-K-ATPase creates electrochemical gradient for Na, which CAUSES A NET FLUX of Na, HCO3, and Cl into the ventricles
how does Na enter the choroid plexus epithelial cells
Na-dependent Cl-/HCO3- exchanger (NCBE)
what two transporters are found on the luminal side of the choroid plexus epithelial cells?
Na-K ATPase
aquaporin
what ion accumulates within the choroid cell, creating a CONCENTRATION gradient
HCO3-
where does the HCO3- and Cl- from within the choroid cell go?
into the ventricle, via apical transporters
what ion accumulates within the choroid cell, creating AN ELECTROCHEMICAL gradient
Cl-
what two values are equal in CSF and serum
osmolarity
Na
is pH more acidic is the CSF or serum
CSF pH is more acidic (7.33)
what two values are greater in CSF than serum
Cl- and CO2
what is absorption of CSF proportional to
intracranial pressure (ICP)
at what ICP does absorption of CSF STOP
<68 mm
what structure absorbs CSF vis what mechanism
arachnoid villi via bulk flow
increasing levels of WHAT in the blood increases cerebral blood flow?
CO2
why do people have headaches after LPs
decreased CSF volume => break is heavier => blood vessels are more easily agitated => PAIN
how does intracranial pressure influence cerebral blood flow
increased ICP osbstructs venous outflow => reduced arterial flow
does SNS or PNS mediate autoregulation of blood flow
SNS!
when BP is high, what does the SNS do to systemic vasculature
VASOCONSTRICT
protects capillaries and BBB
how is systemic BP altered in the event of reduced brain perfusion
activation of vasomotor centers => INCREASE BP
what are circumventricular organs
organs which lack BBB
what substances passively diffuse across the BBB
water
nonpolar substances
CO2
O2
what are the three cellular constituents of the BBB
astrocyte endfeet
pericytes
capillary endothelial cells
how does glucose enter the brain
GLUT1
is GLUT1 insulin dependent?
no
what is the function of p-glycoprotein in the BBB
moves drugs that were able to cross the BBB back into the blood
how is Na-K-2Cl transporter expression regulated
astrocyte signals => endothelin 1 and 3 => increased expression
what glucose transporter is found on neurons
GLUT 3
what glucose transporter is found on microglia
GLUT 5
what are the four circumventricular organs
posterior pituitary
area postrema
OVLT
subfornical organ
what is the function of area postrema?
initiation of vomiting
what is the function of OVLT (orgnum vasculosum of the lamina terminalis)
TARGET OF ANGIOTENSIN II
regulation of total body water, thirst
