6.5a Neurons

03/12/2013 § Leave a comment

The other day I asked Santa if he could give me something for the circles around my eyes. I don’t think he’s going to reply.



page 255, abnormal action potentials

1. Using only the data in Figure 13, outline the effect of reduced Na+ concentration on:

a) the magnitude of depolarisation –> When the sea water is at the lowest (at 1 second), the magnitude of depolarisation decreased.

b) the duration of the action potential –>The reduced sodium levels caused a longer duration of the action potential.

2. Explain the effects of reduced Na+ concentration on the action potential. –> If the levels of sodium are low, that means that the resting potential cannot be low. The concentration gradient across the membrane isn’t high due to the low sodium concentration therefore there would be less active transport thus a smaller magnitude.

3. Discuss the effect of reduced Na+ concentration on the time taken to return to the resting potential. –> Reduced sodium levels increases the duration of action potential and increases the duration of time needed to return to the resting potential. But if there’s a low concentration of sodium ions, that could also mean that the membrane can actively transport sodium faster (because there’s less of them) and thus reduce the duration of time until the resting potential.

4. Compare the action potentials of shaker and normal fruit flies. –> Wild type flies have a higher action potential than mutant flies.  Wild type flies have about a 40 mV action potential peak while mutant only have about 25 mV.

5. Explain the differences between the action potentials. –> Because the K-channels aren’t working properly, it’s harder for the mutant flies to repolarise. Nonfunctioning K-channels limit the body from diffusing potassium across the membrane for repolarisation. A normal wild type fly can still repolarise normally because its K-channels do work.

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