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18 Cards in this Set

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What is Fick's Law?

Jx= - (DxABx/w)deltaC

Direction of flux (Jx) = will be away(-) from diffusion coefficient * the area of the membrane (A) * the partition coefficient all divided by the thickness of the membrane (w) all timesthe difference in concentration across the membrane.
What does this equation describe?

Pi =(n/v)(RT)

What's another way to say (n/v)
Osmotic pressure = the number of particles (n)/(v) the volume of the solution times RT.

n/v = c (concentration)
What does deltaPi=deltaP mean?
The change in tendency of H2O to move (deltaPi) = the hydrostatic pressure (deltaP)
The ability of plasma membrane to store charge is its what?
Capacitance is the ability to store charge
What funcitons like a resistor in cell membrane? How?

What is resistance?
Ion channels function as resistors by deciding how difficult it is going to be for charges to pass through the membrane

Resistance is the measure of difficulty that a current has passing through a substance. (High resistance means low conductance)
What does "g" stand for? What does it mean?

If g is high, what does that mean?
Conductance (think permeability) across the membrane.

If conductance is HIGH then it is EASY for charges to move through the material.
What is the threshold with regard to action potential?
Threshold is the membrane potential at which there is a 50% chance that an AP will be generated.
When is the polarity of membrane potential reversed in an action potential?

What is the part of an AP that is positive called?
At the peak.

The overshoot is positive.
Write the cord conductance equation.

What does it mean?
Vm = (gk/gTot)Ek + (gNa/gTot)Ena + (gCl/gTot)ECl

It means that the MORE permeable the membrane is to a given ion, the more Vm tends toward the equilibrium potential for that ion.
What has the biggest impact on determining Vm?
PERMEABILITY (conductance) is the biggest factor in determining Vm.
Which will have a bigger impact on Vm, changing the permeability (gK) or changing the Ek (concentration)?
THE PERMEABILITY will have a bigger affect on Vm.
What ion are resting membranes most permeable to? Why?
Resting membrane is most permeable to K because Vm is closest to K.
What is this:

Ex = 60log[X]outside/[X]inside

what does it describe?
Nernst Potential.

A theoretical equilibrium potential that you can figure out if you know the concentration for an ion inside and outside of a cell.
When looking at equations, gNa refers to what?

ENa refers to what?
gNa is the permeability of Na.

Ena is the concentration of Na.

The cord conductance equation represents that Vm is made of a WEIGHTED average of the permeability and the concentration of an ion.
What is the primary determinant of resting Vm?
the diffusion of K+ outward along its concentration gradient is the primary determinant of resting Vm.
Does the Na/K Pump create Vm?
NO. Not at all. It seems like it would be but the diffusion of K+ outward along its concentration gradient is the primary determinant of Vm.
What creates the driving force?

What if there is high driving force and low permeability?

The ions will not be able to follow their driving force through the membrane.
What does Na/K-pump do if not control resting Vm??
Pumps 3Na+ out of the cell and 2K+ into the cell to maintain their concentration gradients.