The Membrane Potential Flashcards
Nernst Equation
Eion = k(ln[ion]outside - ln[ion]inside)
or Eion = RT/(zF)ln([ion]outside/[ion]inside)
Eion = 58mV/zlog([ion]outside/[ion]inside)
(The equilibrium potential of an ion is equal to the gas constant times absolute temperature divided by the valence of the ion in question (z) and the Faraday constant times the natural logarithm of the concentration of ions on the outside divided by the concentration of ions on the inside)
Coulomb
the measure of electrical charge of a particle
The quantity of charge transported in one second by a current of one ampere
Charge of a proton
1.6x10^-19 C
Avogrado’s number
6.022x10^23
Number of molecules in one mole of any substance
Faraday constant
The total charge on a mole of any monovalent ion
Potential differences in cells are always expressed in terms of the ___ of a cell relative to the ___.
inside, outside
R =
E (Potential difference/voltage(work)) / I (Current or net flow of charge)
Conductance
Reciprocal of resistance
High salt concentrations are (outside/inside) of the cell
inside
(T/F) The ions on one side cannot interact electrostatically with ions on the other side because the membrane is too thick.
False
The net ____ (+/-) charge on a cell is distributed evenly throughout the cell. (True or false)
negative (-),
false
The rate of flow of an ion across the plasma membrane is determined by
The concentration gradient (the difference in the concentrations of the ion on the two sides of the membrane)
The voltage difference across the plasma membrane
The conductance of the ion channels (the ease with which ions move through the ion channels across the membrane).
RT/F at room temperature
58mV
RT/F at 37 degree celsius
61mV
Donnan equilibrium
The product of the concentration of potassium and chloride ions outside the cell is equal to the product of the concentration of potassium and chloride ions inside the cell (at electrochemical equilibrium, the equilibrium potential for potassium and chloride is equal)
The neuron cell membrane is permeable to (2 ions)
potassium and chloride
Sodium is more concentrated on the ____ of the cell and potassium is more concentrated on the ____ of the cell.
outside,
inside
Sodium potassium pump
3 Sodium and 1 ATP bind to the inside of the protein and the sodium leaves the pump, and 2 potassium ions are pumped in
Goldman equation
Em = 58mV*log( (pK[K+]outside+pNa[Na+]outside+pCl[Cl-]inside) / (pK[K+]inside+pNa[Na+]inside+pCl[Cl-]outside)
Simplified to Em = 58mV*log( ([K+]outside+b[Na+]outside) / ([K+]inside + b[Na+]inside) ), where b = the ratio of sodium to potassium permeability (0.02 in nerve cells) because in nerve cells, the contribution of chloride to the resting membrane potential is quite small
Passive membrane properties
transmembrane resistance (resting),
axial resistance,
membrane capacitance
Input resistance
Change in voltage over current
The specific membrane resistance divided by the membrane area
The units of membrane resistance
ohm cm^2
The specific membrane resistance is a function of ___.
the density of ion channels and their conductance
Axial resistance is due to
intracellular fluid (it’s also known as longitudinal resistance)
Length constant
lambda = the square root of membrane resistance/axial resistance
Defined as the distance over which and electronic potential decrements to 37% of its original peak value
Membrane voltage at any point on the membrane
Vx = V0*e^(-x/lambda)
There are higher concentrations of voltage dependent sodium channels at the ____ and input there will be especially effective.
axon hillock
_____ is responsible for the gradual buildup and decline of potentials.
Capacitance (specifically membrane)
Membrane time constant
tau = the product of membrane capacitance and membrane resistance
time necessary for the electronic potential to decrement to 37% its original peak value.
How to calculate the duration of the synaptic potential
V = Vmax*e^(-t/tau)
