Question

1. A hypothetical neuron has an internal concentration of 15mM Na+ and 140mM K+. The extracellular concentration of Na+ is 150mM, while K+ is 15mM.

a) Using the Nerst equation, calculate the equilibrium potentials for both Na+ and K+. Be sure to show your work.

b) The numbers you generated above do not directly reflect the natural resting membrane(Vm) of the neuron, but indicate the equlibrium potential (Ex) for each ion. The actual resting membrane potential of the neuron is around -65 to -70 mV. Describe the passive membrane properties that establish the resting membrane potential, and include your explanation a description as to why the resting membrane potential is not closer to k+ equilibrium( 90mV).

c) at death, neural membranes reach ionic equilibrium as active processes that maintain ionic gradients cease to funciton. describe the structure and function of the major membrane you generated in 1A, what would be the final new resting membrane potential of our hypothetical neuron after death? What would be the physiological consequences of this new membrane potential?

Answer 1

Nerst's equation

Where, V_eq : equilibrium potential

R: Gas constant 8.314 JK^-1M^-1

T: Temperature in Kelvin:298.15 K

z: Valency

F: Faraday's Constant, 96485 C/mol

Veq= 25.69 x Ln(150/15)

Veq= 25.69 x 2.3025

Veq= 59.156

Where, V_eq : equilibrium potential

R: Gas constant 8.314 JK^-1M^-1

T: Temperature in Kelvin:298.15 K

z: Valency

F: Faraday's Constant, 96485 C/mol

Veq= 25.69 x Ln(15/140)

Veq= 25.69 x -2.23359

Veq= -57.38