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Activation of Membrane Channels

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Membrane potenitals

The greater number of Na + channels open the more positive the inside of the cell becomes and therefore the membrane potential is a positive number and increase as the number of Na + channels open increases. The greater number of K+ channels open, the more negative the inside of the cell becomes and so the membrane potential is a negative number with increasing negativity as the number of K+ channels open increases. The membrane potential is the same when 3 K+ channels are open and 0 Na + channels are open or 5 K + and 0 Na + channels are open because Na + has been rendered impermeable to the membrane so the membrane potential is only being set by K +.
The two monovalent ions have different membrane potential values when relatively more of their respective channels are open because of their concentration gradients across the membrane, which determines the positive or negative value. There is more Na + outside the cell than inside which is why it diffuses into the cell, opposite to the behaviour of K + which there is more of inside the cell that outside.
Question 2)
Increasing the concentration of [K]0 depolarises the cell making the Vm more positive.
Question 3)
The PNa/PK value in resting cells was 0.0223. By making the PNa/PK closer to 1.0, the graph shape was more linear, and making it closer to 0.1 made it a curve that fit the points closer.
Question 4)
Increasing the concentration of [Na]0 increases the amplitude of the action potential and making the membrane potential more positive.
Question 5)
The value of PNa/PK during action potential was 16.8110. The resting potential graph was a curve, because it started from approximately -95.0 mV on the y-axis, because typically the resting membrane potential for cells is no higher the -100 mv. The action potential graph was linear in shape.

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