Course by Bing Wen Brunton (University of Washington) https://www.youtube.com/playlist?list=PLqgZEQsU_8E0l1P9bKR6yKOKPMpoJ_tLR
The neuron doctrine: Neurons are distinct cells that communicate through synapses and don’t fuse together.
Cells have a negative resting potential. Which means the inside of a cell is negatively charged with respect to the outside. It is -60 to -80 mV. The cell has less Na+ and Cl- than the outside but more K+.
Nernst potential is the potential when K+ is at equilibrium between the inside of a cell and the outside. The equilibrium is the balance between the electric gradient and the concentration gradient.
Nernst Equation for K
$$ E_k = \frac{RT}{zF}\ln{\frac{[K^+]_o}{[K^+]_i}} $$
z is the valence of the ion (+1 for K+)
R is universal gas constant 8.3 J/mol
F is Faradays constant 9.6e4 C/mol
Potential is measured in joules per coulomb. 1 V to 1 J / 1 C
RT/F is about 25 mV
The ratio of ions is the main variable
The sodium-potassium pump maintains the concentration gradients of more K and less Na in the cell. This pump is always running and consuming energy to maintain the neuron’s resting potential.
1 ATP → 3 Na+ out, 2 K+ in
25mV * ln(1/5) = -40mV from -75 mV
The Goldman Hodgkin-Katz (GHK) Equation
Nernst equation with concentration ratios of different ions weighted by the permeability to the ion. Formula can be changed to account for higher valency ions.