Ionic Basis of the Action Potential Flashcards
What are the concentrations of Na+ and K+, in and out of the cell, at rest?
1- Out: Na+ 140 mM, K+ 5 mM
2- In: Na+ 10 mM, K+ 140 mM
If the passive diffusion of K+ out of the cell is much larger than its diffusion into the cell, what membrane potential would this result in?
Negative mV
If passive diffusion of Na+ into the cell is much larger than its diffusion out of the cell, what membrane potential would this result in?
Positive mV
What is Ohm’s law?
V = IR
1- V is voltage (V)
2- I is current (amperes)
3- R is resistants (ohms)
What are five characteristics of action potential?
1- Initial depolarisation must reach a critical threshold
2- Once the threshold is attained, the depolarising upstroke is regenerative
3- The potential depolarises, overshoots zero, and peaks around +30mV
4- The response is all-or-none
5- The potential repolarises from the peak of the overshoot back to the resting level
In terms of the cell membrane, what is upstroke associated with?
Increased Na+ permeability
What is depolarisation?
1- Negative to positive resting potential
2- Opening of Na+ channels
3- Na+ rushing in, increasing potential to positive
What is repolarisation?
1- Positive to negative resting potential
2- Opening of K+ channels
How can an inactivated Na+ channel be opened?
Potential must be decreased to -70 mV
Describe the events of action potential.
1- Na+ and K+ channels closed
2- Na+ channels open, leading to depolarisation
3- Na+ channels close/inactivate
4- K+ channels open, leading to repolarisation or hyperpolarisation
5- K+ channels close and resting potential gradually returns to normal
How is the resting potential created?
Potassium ions passively move out of the cell
What is hyperpolarisation?
When the membrane potential is more negative than the resting potential
