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
Describe a K+ channel
Only has 1 gate; the gate opens AND closes slowly
What does V-G mean?
Voltage gated
What is the purose of K+ channels?
Help speed up repolarization
What is the difference between K+ and Na+ channels?
K+ channels only has 1 gate and opens slower than Na+ channels. The Na+ channel has 2 gates and opens and closesly quickly.
What happens when your cell membrane is off?
It can affect how fast we can reset our fast Na+ channels therefore the next action potential will be slower.
Ex) In hyperkalemia the HR will decrease
Describe the action potential in the heart?
It plateaus. The action potential is sustained for a long time.
Driving force depends on what 3 things?
- Charge of the ion
- Concentration gradient
- Charge inside the cell
What does equilibirum potential mean?
Charge thats required on the inside of the cell to prevent the net movement of that ion down its concentration gradient; no net movement into cell
What happens when your membrane potential is equal to your ion permeability?
The ion will not move down its concentration gradient
What happens when your membrane potential is more/less than your ion permeability?
The cell will push the ion in the opposite of its concentration gradient
What does driving force mean?
Motivation to go into the cell
What is a common cardiac rhythm you see with hyperkalemia?
V-fib
