Resting Membrane & Action Potentials Flashcards
What is excitability
Allows cells to establish a means of communication to their own interior or other cells
Define RMP
Starting point for a cell to be potentially excited
What is the extracellular and intra cellular concentration and mv for K and Na
Na 145 (out) 12 (In) 67(mv)
K 4.5 (out) 155 (In) -95 (mv)
What channels most affect RMP
K leak channels
RMP is primarily due to the permeability of plasma membrane to what
K
Is the membrane permeable to Na?
Not so much
Role of ATPase in cell membrane potentials
Move 3 Na outside and 2 K inside cell
Does not contribute much to RMP
RMP of cardiac/skeletal muscle
-80 to -90 mv
RMP of smooth muscle
-60 mv
RMP of Neurons
-60 to -70 mv
Difference in diffusion and electrostatic forces
Diffusion is movement of chemicals down their gradients
Electrostatic is movement of charges to their opposite charges
RMP and K leak channels cause a build up of charges where
+ extracellular
- intracellular
Ach binds to what in muscle NMJ
Nicotinic Ach receptors
How to calc. Electrochemical forces
Diffusion + electrical
What is the equilibrium potential of Na alone
+66 mv
What is the equilibrium potential of K alone
-91 mv
What is the Nernst Equation
E(ion) = (61.5)/Z log(xout/xin)
Z = charge of ion (+/-)
Xout = concentration of ion outside cell
Xin - concentration of ion inside cell
How to calculate driving force
(RMP) - (Eion)
What is driving force
How likely it is for an ion to move in or out of a cell
What does a + DF mean
Efflux of ion
What does a (-) DF mean
Influx of ion
What is inside, outside and E for Cl
Out = 116 In = 4.2 E = -89
K leak channels contribute what E to RMP
-91 mv
Na diffusion contributes what E to RMP
+5
Na/K ATP Pump contributes what to RMP
-4 mv
The more (+) RMP means what
The easier it is to depol.
The more (-) RMP means what
The harder it is to depol.
The resting phase is what number
4
The depol phases is what numebr
0
The repol phases is what numebr
3
What is the main contributer to depol
Voltage gated Na Channels
What do voltage gated K channels do
Open slowly after Na VGC close and help to repol
What do Na VGC do
Open fast, allow for depol, then close quickly
What are the phases of opening for Na VGC
Describe as well
Resting - activation gate is closed and inactivation gate is open
Activation - activation gate opens during intials depol
Inactivation - inactivation gate closes rapidly, can not be moved until membrane potential returns near resting
Phases of hyperpol
K VGC stay open a little too long
More difficult for stimulus to make secondary AP
What are the two refractory periods and define
Absolute - Na channels are either open, or the inactivation gate is closed and and not reopen (another AP cannot be generated)
Relative - inactivation gate is now open and activation gate is closed
Steps in AP
- Rapid opening of activation gate of NA VGC
- Increase in membrane Na permeability
- Delayed closure of Na VGC
- Change in membrane potential initiates opening of more Na VGC
——- THE THRESHOLD IS NOW REACHED———
- Rapid opening of activation gate of Na VGC channels in a pos. Feedback loop
- Slow opening of K VGC
——-THE MEMBRANE IS NOW DEPOL——- and REPOL BEGINS
- Peak action is reached and membrane begins to return to normal
- Na VGC inactivation gates are closed
- K VGC are open
- Membrane permeability to Na decreases and K increases
- K VGC slowly close
DRAW AP!
DRAW and lable all necessary things
