Explain why increasing extracellular K^+ reduces the net diffusion of K^+ out of

Question

Explain why increasing extracellular K^+ reduces the net diffusion of K^+ out of the neuron through the K^+ leak channels. _____ 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? ______ Explain why a change in extracellular Na^+ did not alter the membrane potential in the resting neuron. _____ Discuss the relative permeability of the membrane to Na^+ and K^+ in a resting neuron. _____ Discuss how a change in Na^+ or K^+ conductance would affect the resting membrane potential. ______ What is meant by the term graded potential? ______

Explanation / Answer

Activity 1 :

1) If extracellular K+ is increased, the concentration of intracellular K+ will decrease which causes a decrease in steepness of concentration gradient and few K+ ions would be drawn out.

2) If extracellular K+ iincreases, the intracellular K+ will decrease. Few intracellular K+ ions would lead to the membrane potential becoming less negative. This is what I predicted to happen

3) Because there are less number of sodium leak channels than the potassium leak channels, and also high number of potassium channels are open.

4) Because of the few sodium leak channels, membrane permeability to sodium is very low. The membrane permeability to potassium is high because more of potassium leak channels.

5) Resting membrane potential depends on the extracellular concentrations and the intracellular concentrations of the K+ and Na+  ions. Concentration gradient would change because of conductance which causes either K+ or Na+ ions to flow in or flow out of the cell which would change the resting membrane potential.

Activity 2 :

1) Passive potassium channels are likely present. They are passive but selective.

2) Graded potential means there is a slight difference in charge along the cell, "brief localized changes in membrane potential".

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