4- interogate Flashcards
Differences btwn
EPSP
IPSP
Action Potential
EPSP = depol of postsyn neuron; incr prob of AP firing
IPSP = hyperpol of postsyn neuron; decr prob of AP firing
AP = conduction down axon due to depol to threshold (depends on potential to open VG Na+ channels)
What couples electrophysiologic activity to CNS hemodynamics
How does this cell couple the two?
astrocytes
1) areas of brain with high activity also have high glutamate
2) astrocyte take up glutamate
3) incr intracellular Ca2+
4) release arachidonic acid –> –> EET via P450
5) EET release and hyperpol vessel smooth muscle wall
6) decr vascular tone, incr blood flow
See pg 10 for picture
How does EEG evaluate brain activity?
- what does it measure
- which cell type measure
- why are these cells good to measure
- disadvantage
- temporal vs spatial resolution
measure fluctuation in electrical potential at scalp = summation of EPSP and IPSP
in pyramidal cells of lower layers of cortex
cells closely pack and parallel with synch activity
disadv = interference by skull and scalp
very high temporal, low spatial
How does MEG similar and differ from EEG
similar b/c measure brain activity noninvasively BUT DIFFER B/C measure summation of neuronal activity rather than indiv neuron
MEG = magnetic fields produced by electric potentials to assess neuronal activity
MEG temporal vs spatial resolution
high temporal but low spatial
how do you measure brain activity hemodynamically?
using H215O PET scans
SPECTs
fMRIs
How do PET scans probe hemodynamic properties?
Depends on radionucleotide used
- H215O distributes where water does so for BLOOD FLOW
Process of PET scan mechanism
1) inject pt with radionucleotide tracer
2) radionuclide decay and emit positron that annhilates when contact with electrons
3) produce photons to construct blood flow
4) image subtraction of “brain activity” from pt’s brain image to see areas OVER STIMULATED
What is mechanism of SPECT scan
how is blood flow imaged
SPECT = single positron emission CT
inject gamma emitting radionucleotide into pt’s blood
imaged using gamma camera
What does fMRI measure?
How?
measures hemodynamics based on images constructed of changes in deoxyHgb concentration
change ratio of deoxy: oxyhgb –> change MR signal reflected in images produced
Both EEG and MEG record ___ .
These ___ are the result of ___
electrical signals
result of summation of electric potentials by groups of pyramidal cells parallel in cortex (generally synch)
additive
fMRI and PET scans depict ___ which correlates with neuronal activity
fMRI image ___ based on ___
blood flow
fMRI = blood flow = relative concentration of deoxy to oxyhgb in blood (greater activity, more oxyhgb
PET = H215O isotope = distrib in blood and incr in areas with higher blood flow
