Nervous impulses
- Created by: Anon
- Created on: 06-04-15 12:07
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- Nervous impulses
- Resting potential
- Na+ channels are shut
- K+ channels are open, so the axon membrane is more permeable to potassium ions
- A sodium-potassium pump is constantly moving the ions by active transport
- Na+ is pumped out of the axon
- K+ is pumped into the axon
- For every 3 sodium ions that are pumped 2 potassium ions are pumped
- After being pumped into the axon membrane the potassium ions diffuse back out again
- This causes the outside of the axon to be more positive
- Resting potential is about 65mV
- Action potential
- The stimulus causes Na+ channels to open and sodium diffuses into the axon membrane
- Na+ channels open exponentially: the influx of sodium ions causes yet more channels to open
- When the action potential reaches +40mV the Na+ channels shut and K+ channels open
- Repolarisation
- The K+ channels opening causes potassium ions to diffuse out of the axon membrane
- This causes resting potential to resume and repolarises the axon membrane
- Hyperpolarisation
- During repolarisation there is a temporary overshoot in the electrical gradient
- This overshoot causes K+ channels to shut and resting potential to resume
- Resting potential
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