1. THE Na-K ATPase Pump
Action Potential in a Neuron part 2: Na-K ATPase Pump. Rricketson
11.16.2012 Copyright © 2012 Seaspine. All rights reserved.
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2. THE RESTING POTENTIAL
Resting potential (EK )refers to
the difference between the
voltage inside and outside the
neuron when not propagating an
Cl-
impulse. The resting potential of K+
the average neuron is around -70
Na+
mVT The inside of the cell is 70 Na+
mV less than the outside of the Na+
cell. Na+
K+
Na+
K+
K+
Cl-
K+

3. THE RESTING POTENTIAL-THE NA-K ATPASE PUMP
The Na+/K+-ATPase pump helps maintain membrane
potential.
 Moves 3 sodium ions out and 2 potassium ions in, (removes 1 +
charge) against concentration gradient
 Responsible for up to 2/3 of the neuron’s energy expenditure.
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4. THE RESTING POTENTIAL-THE NA-K ATPASE PUMP
Mechanism (PDB ID 2B8E, 2ZKE
biological assembly)
K+
K+
 Unphosphorylated form binds 3
intracellular Na+ ions while
binding ATP
 Hydrolysis of ATP  ADP +
 Phosphorylation of the pump at
a highly conserved Aspartate
residue; ADP + Pi.
 Phosphorylated form has a low
affinity for Na+  Release
 Pump binds 2 extracellular K+
ions  Dephosphorylation.
 Dephosphorylation high affinity
for Na+ ions. K+ (2)  Released
Na+
K+ ions are transported into the
cell. Na+
Na+
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5. THANK YOU
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