General Neurophysiology Flashcards
most of the CSF is made by ___ the rest is made by whatq
choroid plexus
rest made by tissue that lines the ventricles and blood vessels
2 stage process of making CSF
1) passive filtration of serum: plasma loses proteins and fluid filtered into space
2) HCO3, Cl, and K concentrations controlled by channels on epithelial cells
awauporins also exist
molecules that end up in equal or near so concentrations in both plasma and CSF
Na+, Cl-, and HCO3
concentration in CSF greater than plasma
Mg++
Co2
concentration greater in plasma than CSF
K+
Ca++
protein
glucose
absorption of CSF is proportional to _____
intracranial pressure
- at pressure below 68 = no absorption
- normal pressure = 112
- increased pressure causes damage to neurons
obstructive hydrocephalus
obstruct ability of CSF to get to arachnoid villi
non-obstructive hydrocephalus
process of absorption of CSF is impaired not the ability to get there
how does CSF get out
enters arachnoid villi then the venous sinuses by bulk flow
blood brain barrier passive diffusion molecules
H20, CO2, and O2
-free steroid hormones (most proteins are bound and cannot cross)
getting energy to neurons
glucose is main source -GLUT1 transporter, non insulin dependent 2 forms: 55K on capillaries 45K on astroglia
why is the amount of glucose lower in the CSF than plasma
55k and 45k system can be saturated
transporter that moves ions from CSF to blood
- expression tied to and signal from
- related to concentration of what
Na+/K+/2Cl-
- expression tied to endothelin 1 and 3
- production tied to signal from astrocytes
- may be related to concentration of K+ in CSF
many drugs do cross BBB but are moved back to blood via ____ making them ineffective
P-glycoprotein
BBB function
maintain electrolyte composition
-particularly related to K+ and Vm
protection from toxins
prevent escape of NTs
where is an area in the brain that we want exposed to the blood and how does this occur
circumventricular organs
capillaries do not have tight junctions between endothelial cells
4 regions that fall into circumventricular organ category
1) posterior pituitary: release hormones into blood
2) area postrema: vomiting
3 and 4) OVLT: body water/thirst/blood volume control (angiotensin)
sympathetic innervation to cerebral circulation
NPY and norep
a-adrenergic receptors
leads to constriction when systemic CO/BP increases
parasympathetic cerebral circulation
Ach
VIP
PHM-27
-cause vasodilation
sensory innervation of cerebral circulation is tied to ____ and NTs released are
distension
Substance P
Neurokinin A
CGRP
- all cause dilation
- extremely sensitive to torsion/manipulation–>lead to pain
what happens from a lumbar puncture and CSF loss
lose CSF in brain area so it is heavier and simple motion can cause pain and headache due to torsion of blood vessels
-activation of those afferents will also cause vasodilation and increased blood flow
cerebral blood flow is under ___ control (_____ ____) dictates where in brain blood will go
local
oxygen consumption
as intracranial pressure goes up venous outflow _____ leads to ___
is obstructed
leads to reduced arterial flow
cerebral blood flow is strongly ____ which means what
autoregulated
-held constant over wide range of systemic blood pressures
