BIO304H5 Lecture Notes - Lecture 6: Voltage Clamp, Cell Membrane, Tetrodotoxin
Document Summary
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) Voltage clamp amplifier detects a +56 mv difference between vc and vm. The injected current required to depolarize vmto -9 mv is recorded as an outward capacitative current. In order to keep vm=vc, amplifier b injects current equal and opposite to na+ This is recorded as the early na+current. Response to depolarization - rush out of axon and make inside negative. Then the amplifier adds positive charge back into axon - produces late k+ current. In order to keep vm=vc, the amplifier injects current equal and opposite to k+ This is recorded as the late k+current. Hodgkin and huxley saw in voltage clamp recordings: During a voltage step, the amplifier injects a large amplitude current into the axon to change membrane voltage (vm)
