Question

name and explain the event that happens immediately when a nerve fibre gets stimulated

Answer 1

When a stimulus is applied at a site on tje polarised membrane , the membrane at the site on the polarised membrane , thw membrane at the outer side become freely permeable to Na+ . This leads to a rapid influx of Na+ followed by the reversal of the polarity at that site, i.e., the outer surface of the membrane becomes negatively charged and the inner side become positively charged. The polarity of the membrane at the outer site is thus reversed and hence depolarised . The electrical poential difference across the plasma membrane at the outer side is called the action potential, which is in fact termed as nerve impulse . At sites immediately ahead, the axon membrane has positive charge on the outer surface and a negative charge on its inner surface . As a result, a current flows on the inner surface from site Bto site A to complete the circuit of current flow. Hence , the polarity at the site is reserved , and an action potential is generated at site B . Thus , the impulse is conducted . The rise in stimulus-induced permeability to Na+ is extremely short lived . It is quickly followed by a rise in permeability to K+ . Within a fraction of second , K+ diffuses outside the membrane and restores the resting potential of the membrane at the side of excitation and the fibre becomes once more responsive to further stimulation.
let the point A at outer surface of membrane
and B away from point a outer surface
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