Main Experiment

Hodgkin and Huxley developed a mathematical model of nerve action potentials based on a series of experiments they conducted in the 1950's. They performed their first set of experiments on a squid axon, because it is unusually large. The axon was placed in a bath of sea water. Hodgkin and Huxley then inserted a microelectrode into the axon and applied a voltage stimulus. To evaluate the nerve action potential that occured as the stimulus was applied, they measured the membrane potential during its propagation along the squid axon.

Voltage Clamp

Hodgkin and Huxley's next experiment was the Voltage Clamp experiment. By holding volgage constant, they were able to determine the magnitude and timing of ionic currents. The equation they used to describe the situation was:

I_m=C_m(dV/dt)+I_ionic
where
I_m = the current across the membrane
C_m = a constant
(dV/dt) = the change in voltage with respect to time
I_ionic = ionic currents

(dV/dt) is equal to zero, because Voltage "V" is not changing. Therefore, they were able to determine that the membrane current was the function of the ionic currents. They then used the conductance equations to determine which ion was active at what point in the action potential.

Back to the Models

Home