Transcript 3600L6.html.ppt

Psychology 3600
Action Potential
Saltatory Conduction
Ion Channels
Membrane Currents
Myelinated Axon
Saltatory Conduction
AP Propagation/
Saltatory Conduction
http://www.blackwellscience.com/matthews/actionp.html
AP Properties
1. Threshold
2. All-or-none
3. Frequency coding
4. Passive spread
Action Potential Modification
Patterns of Action Potentials
Sustained Stimulation
Equilibrium Potential
Ion Concentration and Permeability
EK
Equilibrium membrane potential for
potassium is -75 to -100mV.
ENa
Equilibrium membrane potential for
sodium is +40 to +60mV.
Action Potential Boundaries
ENa
EK
An action potential is a rapid change
from a potassium dominated potential
to a sodium dominated potential and back.
Ion Channels
Ion Channels are Holes in the Membrane
Ion Channel Criteria
1. Single channel conductance
2. Ion selectivity
3. Gating
4. Pharmacology
Patch Clamp Recording of Ion Channels
Patch Clamp Variations
Ion Channel Criteria
1. Single channel conductance
2. Ion selectivity
3. Gating
4. Pharmacology
Hydrated Ions
The larger the unhydrated ion in size, the more dispersed is its own
charge and the less strongly it will attract water. This leads to the
incongruous situation of the larger the ion, the less hydrated it is,
and the smaller the relative size of the hydrated whole. Thus,
K+ > Na+, but hydrated K+ < hydrated Na+.
I/V Curve-V=IxR