Voltage Clamp ry to understand how cell generates an action potential by control potential across the membrane However, since you are controlling the membrane potential there are NO ACTION POTENTIALS generated in voltage clamp But useful because we can study the current flow through membrane m=Jc +Jion=Jc Jna+Jk+JL): So what did we learn from voltage clamp 1. Assume Gl is -constant 2. initial current transient to Vm step is Jna(m has the fastest time constant) 3. direction of current flow depends on the"drive"(Vm-Vna) 4. after sometime inactivation()starts and Gna goes down Jna goes down 5. at rest, Jk has the biggest effect( Gk is much bigger than others) Hodgkin-Huxley Model Using what was learned from the voltage clamp, we get the Hh model J Potassium and Sodium conductance depend on the membrane voltage. Vk and Vna do not change with an aP since very little ions are actually transported Jm=Cm m+G(m, I( -Vx)+GN,OOm-VNa)+G(m-V) And now we can fill in the black box in the Core Conductor with Hodgkin-huxley modelsVoltage Clamp: Try to understand how cell generates an action potential by control potential across the membrane. + _ However, since you are controlling the membrane potential: there are NO ACTION POTENTIALS generated in voltage clamp. But useful because we can study the current flow through membrane (Jm = Jc +Jion = Jc + Jna+Jk+JL): So what did we learn from voltage clamp: 1. Assume GL is ~constant. 2. initial current transient to Vm step is Jna (m has the fastest time constant) 3. direction of current flow depends on the “drive” (Vm-Vna) 4. after sometime inactivation (h) starts and Gna goes down � Jna goes down 5. at rest, Jk has the biggest effect (Gk is much bigger than others) Hodgkin-Huxley Model: Using what was learned from the voltage clamp, we get the HH model: GK GNa GL + VK � + VNa � + VL � Jm CM + Vm � Potassium and Sodium conductance depend on the membrane voltage. Vk and Vna do not change with an AP since very little ions are actually transported… m Jm = Cm ¶V +GK (Vm , t)(Vm -VK ) + GNa (Vm , t)(Vm -VNa ) + GL (Vm -VL ) ¶t And now we can fill in the black box in the Core Conductor with Hodgkin-Huxley models: