Electrical gradient

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In neurons, an electrical gradient is used as a mode of information transfer. At resting potential, the nerve is at -70 mV which is maintained by the sodium-potassium pump. This uses ATP to move three sodium ions out of the cell and two potassium ions into the cell. The potassium leak channel also contributes to this resting potential as potassium ions diffuse out of the cell to maintain the potential.This results in an overall positive charge outside the cell and a relative negative charge inside the cell. Due to the difference in electrical charges in the intracellular and extracellular fluid, an electrical gradient is formed. The gradient, if unmaintained, would balance the charges of the intracellular and extracellular fluid, as the sodium ions would move into the cell. The electrical gradient and concentration gradient are always in equilibrium with each other during the resting potential.

When the nerve is stimulated, the sodium ion channels open. Sodium ions then rush into the cell down their diffusion and electrical gradient causing depolarisation, which changes the overall electrical potential of the cell[1]. Once the cell has depolarised, it enters the absolute refractory period because all the sodium ion channels are open so the electrical gradient is not large enough to depolarise the cell again[2].

References

  1. D. Hames; N. Hooper (2005). Biochemistry. 3rd ed. Leeds: Taylor and Francis Group. p161.
  2. D. Hames; N. Hooper (2005). Biochemistry. 3rd ed. Leeds: Taylor and Francis Group. P168-170
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