The two ions that make up the action potential. The clamp half of the voltage clamp.
THE ACTION POTENTIAL · THE ACTION POTENTIAL Objectives: Understand the electrical underpinnings of...
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THE ACTION POTENTIAL Objectives: Understand the electrical underpinnings of the action poten Differentiate between voltage-time, current-time and curr voltage relations Understand the electrical underpinnings of the action poten Understand the general equation for macroscopic membran current Know the Nernst equation and the approximate concentrat of Na+ and K+ ions inside and outside of cardiac cells
Transcript of THE ACTION POTENTIAL · THE ACTION POTENTIAL Objectives: Understand the electrical underpinnings of...
THE ACTION POTENTIAL
Objectives:
Understand the electrical underpinnings of the action poten
Differentiate between voltage-time, current-time and currvoltage relations
Understand the electrical underpinnings of the action poten
Understand the general equation for macroscopic membrancurrent
Know the Nernst equation and the approximate concentratof Na+ and K+ ions inside and outside of cardiac cells
Superior
Vena CavaSA Node
Atrium
AV Node
Purkinje
Tricuspid Valve
Mitral Valve
Ventricle
ECGP
PR QRS
Q
R
S
T
Sir Andrew Fielding Huxley
&
Sir Alan Hodgkin
Cambridge University
Winners of the1963 Nobel Prize
for Physiology.
Axon Action Potential
IC = C dE/dt
Itot = IC + Iionic
Late = K+ curre
TEA sensitive
Early = Na+ cu
TTX sensitive
gK
gNa
gNagK
mV
30 ms
Na+
in
K+
out
IK = gK (Et - EK)
INa = gNa (Et - ENa)
gK = IK
(Et - EK)
gNa = INa
(Et - ENa)
+
+
+
Outside
Inside
‘pore’
‘gate’
Voltage-gated Ion Channel
Outside
Inside
Sodium ionTetrodotoxin (TT
+
+
+
Outside
Inside
Potassium ionTetraethylammonium (TE
N
C2H5
C2H5
C2H5C2H5
+
+
+
+
Single-channel currents recorded from membra
of denervated frog muscle fibres.
Neher E, Sakmann B
Nature 260, 799-802, 1976
Nobel Prize 1991
pA = 10-12 A or 1/1,000,000,000,000th of an Amp
Or
1,000,000 ions per second per channel
