General Neurophysiology Flashcards
production of CSF
choroid plexus (50-70%) remaining in the ventricles
- passive filtration keeping proteins out
- HCO3, K, Cl concentrations controlled by channels on epithelial cells
CSF equal to plasma
Na, Cl, HCO3
CSF greater than plasma
Mg - due to NMDA R
CO2
CSF less than plasma
K - neuronal activity will increase so want low to start
Ca - limit NT release
protein - decrease buffering capacity
glucose - taken up for energy
absorption by arachnoid villi
endothelium of sinus and the membrane on the vlli have fused
bulk flow of CSF into venous plexus in the main location
alos pinocytosis
absorption and intracranial pressure
proportional
below 68 - none
normal - 112
role of CSF
protect the brain
two components that limit exchange
tight junctions b/w endothelial cells
glial end feet come in close contact w/ BV increasing diffusion distance
molecules that use passive diffusion across BBB
H2O
CO2
O2
free steroid hormones (most are bound)
glucose and BBB
cannot freely cross
55K GLUT 1 allows across capillary
45K GLUT 1 allows across astroglia
Na/K/Cl cotrasporter
moves all ions from CSF to blood
control K in CSF
drugs and the BBB
drugs cross but are moved back into the blood by P-glycoprotein
functions of the BBB
protect CSF from blood borne agents
maintain electrolyte composition
protection from toxins
prevent escape of NT
posterior pituitary
modified neural tissue that releases hormones into the blood
area postrema
will sense blood born substances leading to vomiting
OVLT and subfornical organ
control body water/thirst/blood volume so must measure blood osmolarity
symp inn arterial blood flow
Norepi and NPY
alpha adrenergics
constriction when systemic CO/blood pressure increases
parasymp inn arterial blood flow
ach, VIP, PHM-27
vasodialation
sensory inn arterial blood flow
substance p - dilation
neurokinin a - dilation
CGRP - dilation
increase of blood flow will return intracranial volume closer to normal
