HMB200H1 Lecture Notes - Lecture 4: Voltage Clamp, Tandem Pore Domain Potassium Channel, Threshold Voltage
Document Summary
When more than one channel opens, can break down the problem to individual channels (ions seem to move independently) Since concentration gradients don"t change, only variable will be electrical gradients. Permeabilities of different ion channels are the same, new em is sum of e for the 2 ions. Using voltage clamp, you can change voltage. Small k+ leak channels vary linearly with voltage changes through simple v=ir (ohm"s. When voltage changed to -9mv, huge non-linear change in current that first depolarized the membrane then repolarized it. Transient rise in na+ permeability (na channels opening then closing, voltage moves through ena) Transient rise in k+ permeability (way above leak current levels, k+ channels opening then closing voltage returns towards ek) Both sodium (1st) and potassium (2nd) voltage-sensitive channels are attuned to the threshold voltage of about -50 mv. If cell membrane changes to reach voltage, both types of channels open to allow ion flow across the membrane.
