L7 Action Potential Flashcards Preview

Physiology > L7 Action Potential > Flashcards

Flashcards in L7 Action Potential Deck (13):

What happens when you inject depolarizing current into a membrane?

the membrane potential will become less negative

you are decreasing the negative charge inside the cell


What happens when you inject hyperpolarizing current into a membrane?

the membrane potential becomes more negative

increase negative charges inside the cell


What does injecting hyperpolarizing current do?

produces a passive electrical response


What does injecting a depolarizing current do?

decreasing the negative charge inside the cell and

produces and action potential

when you reach threshold


How is the rising phase of the action potential produced?

by an increase in Na+ conductance (fast Na+ channels)

As the rising phase progresses the conductance of Na increases until we reach the peak.

As we move closer to E Na, the driving force decreases and conductance of Na decreases at the peak

There is a net inward ionic current because a + charged ion (Na) is entering the cell


How is the decay phase of an action potential produced?

By a decrease in Na+ conductance and an increase in K+ conductance

This is due to delayed rectifier K+ channels

At the peak of an action potential, conductance of K increases, K+ leaves the cell, and there is a net outward ionic current

The conductance of K decreases as we reach closer to E K and the most hyperpolarized state.

As Vm gets closer to E K, K+ channels close and we move back towards the resting potential.



Where is there no net ionic current during an action potential?

At the peak


Fast Na channels have what two types of gates?

sensitive (rapid) activation

inactivation gates


What type of gate does delayed rectifier K+ channels have?

voltage sensitive activation gates


What is fast Na+ channel activation responsible for?

Absolute and relative refractory periods


What is an absolute refractory period?

Inactivation gates are closed

A new action potential cannot be produced


What is the relative refractory period?

A new action potential can be produced, but the threshold is higher.


What is the only cell type with a plateau phase?

cardiac cells