Physioex 9.0 Exercise 3 Activity 1

Membrane potential, Potassium, Potassium channel

Review Sheet Results

1. Explain why increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leak channels.
Your answer:
If the extracellular K+ increases then the concentration of intracellular K+ will decrease causing a decrease in the steepness of the concentration gradient and fewer K+ ions would be drawn out.

2. Explain why increasing extracellular K+ causes the membrane potential to change to a less negative value. How well did the results compare with your prediction?
Your answer:
If extracellular K+ is increased then the intracellular K+ will decrease. Fewer intracellular K+ ions would result in the membrane potential being less negative. This is what I predicted to happen.

3. Explain why a change in extracellular Na+ did not significantly alter the membrane potential in the resting neuron? Your answer:
There are less sodium leak channels than potassium leak channels, and more of the potassium channels are open.

4. Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron. Your answer:
Membrane permeability to sodium is very low because there are only a few sodium leak channels. The membrane is more permeable to potassium because of the higher number of potassium leak channels.

5. Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential. Your answer:
The resting membrane potential depends on the intracellular and extracellular concentrations of the Na+ and K+ ions. Conductance would change the concentration gradient causing either Na+ or K+ to flow into or out of the cell which would change the resting membrane potential.
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