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Depolarization of axolemma during nerve conduction takes place because of :
A
Equal amount of $Na^+$ and $K^+$ move out across axolemma
B
$Na^+$ moves inside and $K^+$ moves more outside
C
More $Na^+$ outside
D
None
Detailed Solution
At rest, the inside of the axon is negative (about –70 mV).
When stimulated, voltage-gated $Na^+$ channels open and $Na^+$ ions rush into the axon, so the inside becomes positive (depolarisation, about +30 mV).
Then the $K^+$ channels open and $K^+$ moves out, restoring the negative potential (repolarisation).
So, as per the answer key, depolarisation involves $Na^+$ moving inside, with $K^+$ moving outside afterwards.
When stimulated, voltage-gated $Na^+$ channels open and $Na^+$ ions rush into the axon, so the inside becomes positive (depolarisation, about +30 mV).
Then the $K^+$ channels open and $K^+$ moves out, restoring the negative potential (repolarisation).
So, as per the answer key, depolarisation involves $Na^+$ moving inside, with $K^+$ moving outside afterwards.