Question
How is an action potential achieved during impulse conduction through an axon? Explain.
✓
Answer
- When the polarised membrane of a resting axon is stimulated at a site (A), the permeability of the membrane is changed at that site; it becomes more permeable to sodium ions.
- So, there is a rapid influx of Na+ ions that leads to the reversal of the polarity, i.e. the exterior of the membrane becomes negatively charged and the interior/axoplasm becomes positively charged.
- The electrical potential difference across the membrane at the stimulated site (A), is called action potential.
- The site (B) ahead of A, is in the polarised state, i.e. it is positively charged on the outside and negatively charged on the inside.
- Consequently, there is a flow of current from site A to B in the axoplasm and from B to A on the extracellular fluid and an action potential is generated at B.
- These events are repeated all along the length of the axon and the impulse/ action potential is conducted.
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