Computer Simulation of Neurophysiology.ppt

Computer Simulation of Neurophysiology
Presented in Lab
Computer Simulation of Neurophysiology
Action Potential Stimulation
Determine threshold
Observe effects of other stimuli
Effects of Drugs
Determination of Conduction Velocity
Action Potential Generation:Stimulus
Action potentials are triggered by membrane depolarization at the axon hillock
Depolarization caused by increased permeability to ions
Permeability typically increased by chemically-or physically-gated ion channels
Can also be affected by membrane perturbations, changes in ion gradients, etc.
Threshold and “All or None”
Action potentials are driven by the opening of voltage-gated ion channels
Require a minimum amount of depolarization for any to open = threshold
Once some open, they in turn cause others to open
“All or none” response for single neurons
Stimulus Intensity
Threshold
Neuron Axon Response
Compound Action Potentials
Extracellular recordings of whole nerve segments
Many axons w/ variable thresholds
Different degrees of stimulation
Amplitude of Action Potential varies with stimulus strength
Vary NUMBER of axons undergoing AP
Does NOT violate “all or none” principle
Action Potential Amplitude
Stimulus Intensity
Compound Action Potentials
Subthreshold stimulus
No AP
Threshold stimulus
pound AP
Submaximal stimulus
Variable number of axons undergo AP
Variable amplitude
Maximal stimulus
Maximum amplitude
Does not vary with stim strength
subtheshold
threshold
submaximal
maximal
Action Potential Amplitude
Stimulus Intensity
Nerve signaling and drugs
Signal conduction within a neuron occurs through action potentials
voltage-gated channels
Signal conduction from one nerve to another occurs through synapses
Chemically gated channels
Neurotoxins could affect nerve signaling at either site
Lecture Text
Neurotoxins
Affect voltage-gated ion channels (alter APs)
Tetradotoxin, novocain – block . Na+channels
Scorpion venoms – keep Na+ channels open and K+ channels closed (prolon