Choose the option that shows the correct sequence of the following steps involved in the generation and conduction of a nerve impulse. I. The number of cations inside the axon increases. II. Na+ ions

Question

Choose the option that shows the correct sequence of the following steps involved in the generation and conduction of a nerve impulse.
I. The number of cations inside the axon increases.
II. Na+ ions diffuse into the neuron from the ECF.
III. Membrane potential changes from -70 mV to about +30 mV.
IV. Application of stimulus make membrane of nerve fibre more permeable to Na+.

TestHub · Accepted Answer

When a stimulus is applied to a nerve fibre, the resting membrane becomes more permeable to $N a^{+}$ ions.

This increased permeability causes $N a^{+}$ ions to rapidly diffuse into the neuron from the extracellular fluid (ECF).

The influx of $N a^{+}$ ions leads to an increase in the number of cations (positive ions) inside the axon.

As a result of this accumulation of positive charges, the membrane potential changes from the resting value of $- 70$ mV to about $+ 30$ mV, generating an action potential (depolarization).

Thus, the correct sequence of events is IV $\to$ II $\to$ I $\to$ III.

Answer: IV $\to$ II $\to$ I $\to$ III

Biology - Neural Control and Coordination Question with Solution | TestHub

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