Lecture 4 Flashcards
Bioelectricity
Bioelectricity
Membrane potential
Measurement of Vm
Measured in a similar way to patch-clamp
Reference electrode used
measures different between the reference electrode and one in the cell
Sharp electrode and smaller than PC method
Determination of Vm
Unequal distribution and the selective movement of a few ions
Na+ extracellular concentration
150mM
Na+ intracellular concentration
15mM
K+ extracellular concentration
5mM
K+ intracellular concentration
150mM
A- intracellular concentration
65mM
A- extracellular concentration
0mM
Na+/K+ ATPase
Maintains ion distribution
3 Na out and 2 K out
Direct contribution to the Vm of 20%
Electrogenic - causes loss of one +ve charge
indirectly controls intracellular Na+ and K+ levels
K+ channel contribution
K+ exits cell to leave negative charge
Negative charge attracts K+ into the cell from ECF
Eventually reaches equilibrium - no net movement of ions = no current
Nernst Equation
Eion=RT/zF x Ln[ion]out/[ion]in
Nernst Eion
Equilibrium potential
Nernst R
Gas constant
Nernst T
Temperature in Kelvin