Interrogating the Nervous System

Question 1

EPSP vs. IPSP vs. Action Potential

Answer 1

• EPSP = excitatory post synaptic potential = moves membane potential towards threshold
• IPSP = inhibitory post synaptic potential = moves membane potential away from threshold
• EPSP/IPSP = temporary membrane changes ==> spatially and temporally summated to generate all or none response of action potential

Question 2

Electrophysiologic activity and CNS hemodynamic “coupling” definition

Answer 2

• astrocytes form a coupling between neurons and blood supply
• generate local increases in blood flow to areas of increased synaptic and other metabolic activity
• measurement of cerebral hemodynamics and regional blood flow = indirect measure of the activity of populations of neurons

Question 3

Techniques for evaluating “brain activity” using electromagnetic properties of nervous system

Answer 3

• Electoroencephalogram (EEG)
• Electromyography (EMG)
• Magnetoencephalography (MEG)

Question 4

Techniques for evaluating “brain activity” using hemodynamic properties of nervous system

Answer 4

• PET
• SPECT
• fMRI

Question 5

EEG characteristics/fxn

Answer 5

• measure electrical potentials @ scalp
• frequencies/wave patterns indicate states of being
  
  • Relaxed vs. Alert vs. Drowsy vs. REM vs. Dreamless
• generally: higher frequency = more active vs. lower frequency = less active

Question 6

MEG characteristics/fxn

Answer 6

• records magnetic fields produced by electrical currents in populations of synchronized neurons

Question 7

fMRI characteristics/fxn

Answer 7

• synaptic activity ==> regional changes in deoxyhemoglobin concentration
• images change due to nature of magnetic properties of hemoglobin
  
  • oxyhemoglobin is diamagnetic and does not cause distoriton in a magnetic field vs.
  • deoxyhemoglobin is paramagnetic and does distort magnetic fields

Question 8

PET characteristics/fxn

Answer 8

• FDG-PET uses radiolabeled glucose
  
  • active parts of brain attract more glucose ==> radiolabeled glucose seen on PET
• H₂O¹⁵-PET uses radiolabeled water
  
  • active parts of brain attract mroe blood flow + water ==> active parts of brain seen on PET