Lecture 5 Flashcards
End of exam 1 material
What does cell polarization mean?
A difference in electrical charge between in inside and outside of cell.
When is a cell polarized?
At rest; the inside of the cell is negative
What is the normal polarity of a cell at rest?
About -80; negative
What is depolarization?
Happens during an action potential; when the cell is stimulated/turned on; the cell becomes more positively charged which is less polar.
What is hyperpolarization?
Happens during/after repolarization; Cell polarity becomes more negative than the resting cell polarity.
What happens when a cell is more negatively charged?
Cell becomes more difficult to excite
What is repolarization?
Happens after depolarization when you return back to V(rm); anything that makes the cell more negative after an action potential.
What happens during depolarization?
Sodium channels open and rushes into the cell and pNa+ increases; membrane potential will become closer to Nernst for Na+
What happens during hyperpolarization?
Increase in potassium channels opening; Membrane potential becomes even closer to Nerst for K+; Deals with the AV node in the heart.
What happens to the cell when the polarity of the cell goes above 0?
The Na+ channels are opening and the cell becomes more permeable to Na+ than K
What is happening during repolarization?
Na+ channels are closing and the K+ channels are opening
Why does hyperpolarization happen?
It is a result for the slowly closing K+ channels
What contributes the membrane potential?
Leaky K+ and Na+ channels
What drugs affect the V-G Na+ Channels and how?
-caine
Affects the activation gate of sodium channels
At rest, the activation gate for Na+ channels are_____
Closed
What are 2 traits of the Na+ channels?
Fast and highly selective
What is the M-gate? Where is it located?
Activation gate
On the outside of cell
What is H-gate? Where is it located?
Inactivation gate
On the inside of cell
Describe a Na+ channel in a resting cell?
The M-gate is closed and the H-gate is open
Describe a Na+ channel in an activated cell?
Both M- and H- gates are open but H- gate will close immediately; Na+ will flood into cell for a short period of time
Why does the resetting of ion channels need to be quick?
To get ready for another action potential; especially important in the heart
Describe a Na+ channel in repolarization?
The channel will go from having the H gate closed;
The M- gate will close
The H gate will open; process starts over. Na+ channel ready for another action potential
Describe a K+ channel during rest.
The gate is closed
Describe a K+ channel during activation?
The K+ channel gate slowly open
