Membrane Physiology: Resting and Reversal Potentials Flashcards
What can disrupt the resting membrane potential of a cell?
A change in ion concentrations either inside or outside of a cell
The larger the membrane potential the larger…?
The ability to do work
What is used to do work in cells?
Difference in ion concentrations
What determines the movement of ions?
The sum of differences in the electrical and chemical (concentration) gradient
What is meant that RMP is in equilibrium?
The net influx is equal to efflux of ions
Which ion has the greatest affect on the membrane potential?
The most permeable one
Is K+ concentration or chemical gradient stronger?
Concentration gradient
What is the relative concentration difference of Na+ inside and outside of the cell?
x10 more outside the cell
What is the relative concentration difference of K+ inside and outside of the cell?
x40 more inside the cell
What is the relative concentration difference of Ca2+ inside and outside of the cell?
x25k more outside the cell
What is the relative concentration difference of Cl- inside and outside of the cell?
x30 more outside the cell
What does the magnitude of the electrical force depend on?
The membrane potential
What does the direction of the electrical force depend on?
Ion charge
What is the net force?
Sum of chemical + Electrical gradient
How does each ion attempt to change the membrane potential?
Each ion tries to move the membrane potential towards its equilibrium potential
Why is the equilibrium potential also called the reversal potential?
Because the typical concentration gradient is reversed
What is Cl- Erev?
-90 mV
What is Na+ Erev?
+65 mV
What is Ca2+ Erev?
+130 mV
What is K+ Erev?
-95 mV
What three terms are synonymous?
Nernst Potential, Reversal Potential, Equilibrium Potential
What is an equilibrium potential?
The membrane potential at which the force of the concentration gradient = electrical gradient
What is the Nernst equation?
Ex= (60mV/z) log ({X}o/{X}i)
What does z stand for in the Nernst equation?
Valence number of electrons including the charge
What value does a number less than one carry on the log scale?
A negative
What is the net driving force?
Membrane potential-Erev
Current MP-Reversal Potential
What is a local potential?
A depolarization of the membrane by an influx of Na+ at a specific point on the membrane only
What is another name for a local potential?
Graded response
What happens if another Na+ opens next to the initial channel?
It will have an additive affect causing the membrane to become more depolarized
What happens to the Na+ that has entered the membrane?
It diffuses throughout the inside of the dendrite getting less concentrated as it moves
What happens to a local response?
It degrades over space and time
What is another term for local potential?
Synaptic potential
Where do local potentials mostly occur?
In dendrites and somata of neurons
What happens when a sufficient number of depolarizing synaptic potentials occur?
The axon initial segment will become depolarized
What is a significant depolarization?
A depolarization of about 10 mV
What is an action potential?
A propagated potential that travels along the axon of a neuron
What are the properties of Na+ channels?
Open quickly to a small depolarization
What are the properties of K+ channels?
Open slowly to a large membrane depolarization; involved with action potential termination
What is the refractory period?
The time period in which Na+ channels are inactivated by the inactivation gate to ensure unidirectional propagation of the AP
What is the absolute refractory period?
When the Na+ gates are inactivated and absolutely no AP can occur
What is the relative refractory period?
Another AP can be produced only if the stimulus is large enough (while the K+ channels are still closing)
What is peripheral neuropathy?
Loss of peripheral myelin which slows conductance
