Lecture notes. Taken in part from: Adley, D. J. (1991) The Physiology of Excitable Cells , Cambridge,3ed. Calabrese, R. C., Gordon, J., Hawkins, R., & Qian, Ning. (1995) Essentials of neural Science and Behavior. Study guide and practice problems . Appleton & Lange
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PHYSICAL PROCESS THAT EQUILIBRATES FREELY MOVING SUBSTANCES
0.1 M NaCl = 0.1 M Na + 0.1M Cl = 0.2 Osm
Voltage should be thought of as a gradient. A gradient implies looking at two places or states with respect to one another.
If Compartment 1 is the reference chamber, Compartment 2 is said to be positive with respect to compartment 1. (A volt meter will point toward the positive pole).
If the compartment 2 is the reference chamber, compartment 2 is negative with respect to compartment 1. (The voltmeter will point to the left chamber).
2) This can be thought of as an electromotive force.
Charge separation gives rise to a difference of electrical potential (volts).
The voltage across the membrane (Vm) is called: membrane potential.
Vm = Vin - Vout
3) Think of this voltage as a driving force for the movement of charges in space.
We will use the convention that the direction of current flow is the direction of the net movement of the positive charges (Franklin’s convention)
That is, in ionic solutions cations (+ charges) move in the direction of the electrical current
V = RI
Where V is in volts, R is resistance, in ohms and I is in amperes. R is the slope of the line relating volts to current
δW =increment of work
δn = increment of number of moles moved.
R =gas constant (8.314 J deg-1 mole-1)
T =absolute temperature
X =molar concentrations of solute in
compartment 1 an 2
δWe = δn (zFE)
δWe = increment of work.
δn = moles moved against an electrical
Z = valence of the ion moved.
F = Faraday’s constant(96,500).
E = the potential difference between the