A hypothetical neuronal cell shows the following intracellular and extracellular concentration of sodium, potassium, calcium, and chloride ions. Extracellular concentration (mM) Intracellular concentration (mM) (Ion)out/ (Ion)inside E ion at 37 oC Sodium ion 420 60 Potassium ion 25 420 Calcium ion 16 0.4 Chloride 565 45 How does increase in the extracellular potassium concentration to 250 mM affect the Nernst potential? Why?
Please ASAP. Thank you.
A hypothetical neuronal cell shows the following intracellular and extracellular concentration of sodium, potassium, calcium, and chloride ions.
|
|
Extracellular concentration (mM) |
Intracellular concentration (mM) |
(Ion)out/ (Ion)inside |
E ion at 37 oC |
|
Sodium ion |
420 |
60 |
|
|
|
Potassium ion |
25 |
420 |
|
|
|
Calcium ion |
16 |
0.4 |
|
|
|
Chloride |
565 |
45 |
|
|
- How does increase in the extracellular potassium concentration to 250 mM affect the Nernst potential? Why?
The equilibrium or Nernst potential is the membrane potential at which there is no net flow of ions across the membrane. It depends on the concentration of ions across the membrane which creates a gradient for the flow of ions and increases with the increase in the concentration gradient.
In a neuronal cell, the concentration of K+ ions outside the cells is significantly lower than that inside the cell. This means that the K+ ions tend to move out of the cells down their concentration gradient. At negative potential, the K+ ions flow from inside to outside the cells, and at positive membrane potential, the direction is reversed. Thus, the membrane potential at which the movement of the K+ ions across the membrane is zero represents the Nernst potential for potassium.
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