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
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?