• Lecture 2
• Resting potential,
Measurement of Ion Movement
• Membrane Potential in
Excitable Cells 1:
• Voltage-gated channels & the
basis of the Action Potential
Some useful physical constants
From Bertil Hille, Ion Channels of Excitable Membranes, 3rd edition
Driving Force: Vm - Ex
I = g Vm
IK = gK (Vm – EK)
EK = 61 log (150/ 150) = 0 mV
EK = 61 log (150/ 45) = + 32 mV
EK = 61 log (30/ 150) = - 43 mV
At the resting membrane potential the
individual ionic currents sum up to zero
I=gV
At rest IK = -INa
IK = gK (Vm – EK)
gK (VR – EK) = -gNa (VR – ENa)
INa = gNa (Vm – ENa)
If gK:gNa = 5, solve for VR
VR = -64 mV
VR = (ENagNa/gK+gNa) +
(EKgK/gK+gNa)
Voltage Clamp
The Patch-clamp technique
Patch clamping a neuron
Recordings of a single cardiac K channel
and its current-voltage characteristics
Recordings of a whole-cell CNG current and its
I-V characteristics
A model of a voltage-gated channel protein
The depolarization-induced biphasic
current of squid giant axons
Inward sodium and outward currents
Sodium and Potassium whole-cell currents