Depolarisation (A-level Biology)
Depolarisation
Reaching the Threshold Potential
Changes in Membrane Permeability
- Any stimulation of an axon causes some of the sodium channels to open. When an axon is stimulated, some of the sodium channels will open. This leads to the movement of Naᐩ ions.
- Naᐩ ions diffuse down a gradient. The Naᐩ ions diffuse down their electrochemical and concentration gradient back into the axon. This makes the inside of the neurone less negative and reduces the potential difference across the membrane.
- The bigger the stimulus, the more channels open. When the stimulus to the axon is large, more channels will open. This allows more Naᐩ ions to diffuse down their gradient.
- The membrane depolarises after threshold is reached. If the potential difference reaches the threshold (-55mV), the membrane becomes depolarised. Voltage-gated sodium channels open (these are channel proteins in the cell membrane that allow the movement of charged particles).
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