Question

You are studying the permeability on Voltage-Gated Sodium Channels involved in action potential

generation. Predict what would happen to the permeability of Sodium in the following cases (would it decrease, increase or stay the same?). Explain why you chose your answer.

i.Increased receptor number.

ii. Add a drug that make channel stay open longer.

iii. Raise Vm above+35mV.

iv.Lower Vm below -70mV.

v.Add a drug that prevents channel opening.

vi. Add more Na+ to the extracellular environment.

Answer 1

Answer :)

Answer i)

If we increase receptor numbers, then permeability of sodium ions will also increase. This is because more receptors can cause quick activation due to fast movement of sodium ions.

Answer ii) this will also increase sodium permeability because channels will remain open, which allows more sodium ions to move.

Answer iii) raising Vm above +35 mV will decrease the flow of sodium ions. It can increase the flow of potassium ions.

Answer iv) lowering Vm value can increase more sodium ions flow. Lowering Vm will cause the increasing of voltage that can occur due to Na⁺ ions influx.

Answer v) this will drastically decrease the sodium ions flow.

Answer vi) this cannot increase sodium permeability because extracellular matrix is also contain more sodium ions than intracellular. This time increasing sodium ions will cause potassium ions efflux.

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