Exam 1: Action Potentials Flashcards
Define cell polarization
A difference in electrical charge between the inside/outside of the cell
When cells are polarized they are _____ at rest
Negative
Define depolarization
To become less polar (or more positively charged); usually stimulated or turned on
Define hyperpolarized
To become more polar (or more negatively charged)
Define repolarization
To return to resting membrane potential from a depolarized state`
Which ion comes into the cell during depolarization?
Sodium
During depolarization which direction does the membrane potential go?
Towards the Nernst for Na (more positive)
During repolarization which ion channels open even more?
Potassium channels
Are sodium channels fast or slow?
Fast
Are potassium channels fast or slow?
Slow
How many gates do sodium and potassium channels each have?
Sodium = 2
Potassium = 1
What are the two gates in sodium channels?
Activation gate = aka M gate
Inactivation gate = aka H gate
T/F The activation gate is open when the cell is at rest
False; the activation gate is closed when the cell is at rest
If the gate was open while at rest, sodium would be coming into the cell when we don’t want it to
When does the activation gate open?
When the cell depolarizes to the threshold potential
Which drugs affect sodium channels at the site of action on the ECF side?
-caines
Ex: Lidocaine
T/F The inactivation gate (in sodium channels) is closed when the cell is resting
False; it is open while resting
After the activation gate opens what occurs?
Sodium quickly comes into the cell and then the inactivated gate closes quickly, leading to the activation gate also closing
What would happen if we kept the inactivation gate open while closing the activation gate?
More sodium would come into the cell
What must happen with the membrane for the inactivation gate to open again?
The membrane must repolarize
How do we get a cell back to Vrm?
Open additional potassium channels to help “repolarize” the cell after we wind down an action potential
