Electrical Signal Conduction: Resting Potential / Action Potential
Nerve cells, called neurons, use both active and passive transport to send signals throughout the
body. Protein pumps (active) and protein channels (passive) in the membrane are involved in this
process. The protein pumps in a neuron are called sodium-potassium pumps.
RESTING POTENTIAL
When a neuron (nerve cell) is not transmitting an impulse, the
sodium-potassium pumps in the cell membrane are transporting
three sodium ions (Na+) out of the cell for every two potassium
ions (K+) pumped into it. This creates a build-up of sodium
outside the cell and a build-up of potassium inside – which are
called gradients. This creates more of a positive charge on the
outside the cell as compared to the inside. This difference in
charge across the membrane is called the resting potential.
ACTION POTENTIAL
When a neuron picks up an impulse, it opens sodium channels and sodium diffuses in through
facilitated diffusion. For a brief moment, that part of the membrane becomes more positively
charged INSIDE (the charge switches). This sudden reversal of charge across the membrane is
called an action potential. This change causes other sodium channels to open (like a domino
effect). So this reversal of charge moves down the nerve cell.
After the impulse passes, the sodium channels shut, the potassium channels open allowing
potassium to flow out (again by facilitated diffusion). This reverses the charge back to where it
started. Then the sodium potassium pumps recreate the resting potential by actively pumping
sodium out and potassium back in.
PART B: Answer these questions based on information from the reading.
1. When the neuron is resting, a high concentration of sodium is INSIDE / OUTSIDE the cell.
2. When the neuron is resting, a high concentration of potassium is INSIDE / OUTSIDE the cell.
3. Name the pumps responsible for creating this condition.
4. Describe how these pumps work:
___________________________
_____________________________________________
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5. What type of transport is demonstrated at this point? PASSIVE / ACTIVE
6. Resting potential =
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7. When an impulse moves down the neuron, sodium moves INTO / OUT OF the cell.
8. By what process does sodium move?
_____________________________________________
9. What type of transport is this? PASSIVE / ACTIVE
10. Action potential = _______________________________________________________________
______________________________________________________________________________
11. AFTER an impulse moves down the neuron, potassium moves INTO / OUT OF the cell.
12. By what process does potassium move? _____________________________________________
13. What type of transport is this? PASSIVE / ACTIVE
14. Then the _______________________________________________ restore the resting potential.