If membrane potential is clamped to -100 mV (for example by patch clamp) with Nernst potential for sodium of +60 mV and for potassium of -90 mV the following will happen?

Question

If membrane potential is clamped to -100 mV (for example by patch clamp) with Nernst potential for sodium of +60 mV and for potassium of -90 mV the following will happen?

1. K+ efflux out of the cell and Na+ influx into the cell 
2. K+ and Na+ influx 
3. K+ and Na+ efflux 
4. Na+ efflux out of the cell and K+ influx into the cell 
5. Nothing will happen 

Answer 1

To understand what happens in this scenario, we can analyze the driving forces on potassium (K⁺) and sodium (Na⁺) ions based on the membrane potential and their respective Nernst (equilibrium) potentials.

1. Given Data:
2. Membrane potential (Vm): -100 mV
3. Nernst potential for Na⁺ (ENa): +60 mV
4. Nernst potential for K⁺ (EK): -90 mV
5. Interpretation of Ion Movement:
6. For K⁺:
7. The membrane potential (-100 mV) is slightly more negative than EK (-90 mV).
8. Since Vm is more negative than EK, potassium ions (K⁺) will experience a small driving force to move out of the cell (efflux).
9. For Na⁺:
10. The membrane potential (-100 mV) is much more negative than ENa (+60 mV).
11. This creates a large driving force for Na⁺ ions to move into the cell (influx).
12. Conclusion:
13. With the membrane potential clamped at -100 mV, K⁺ will efflux out of the cell, and Na⁺ will influx into the cell.

Correct Answer:

K⁺ efflux out of the cell and Na⁺ influx into the cell