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Neural Control and Coordination — BIOLOGY STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 ScienceBIOLOGYNeural Control and Coordination3 Marks
Question
How is an action potential achieved during impulse conduction through an axon? Explain.
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Answer

  1. 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.
  2. 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.
  3. The electrical potential difference across the membrane at the stimulated site (A), is called action potential.
  4. 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.
  5. 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.
  6. These events are repeated all along the length of the axon and the impulse/ action potential is conducted.

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