BIO304H5 Chapter 5: 304 9
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If vc-vmis negative (e. g. -85 mv --65 mv = -20 mv), amplifier binjects negativehyperpolarizing current: this process continues dynamically until the two inputs into amplifier. Example voltage clamp experiment: use vcto hold voltage at -65 mv, at the onset of the voltage change pulse, vcis changed to -9 mv, so the voltage clamp amplifier bquickly injects current into the axon raising. Vmto -9 mv: vcholds the vmat -9 mv for 5 milliseconds (ms, vcis then changed back to -65 mv, which returns vmback down to -65 mv. This is what hodgkin and huxley saw in their first voltage-clamp recordings 3. a late current: notice how nice and flat vmstays during the voltage clamp step, compared to the ap, can study gnaandgkat fixed voltages! Understanding na+and k+currents recorded with the voltage clamp: say we have a holding voltage of -65 mv, voltage clamp amplifier does not detect a difference between the command voltage (vc) and the membrane voltage (vm, nothing happens.
