Question

A mutation slows sodium transport across the axon membrane tenfold. Predict the effect of the mutation on nerve function in unmyelinated axons. What if an equivalently slowing mutation also happens to potassium transport? What would the effect of one or both mutations be on myelinated axons?

Answer 1

The effect of mutation on nerve function in unmyelinated axons is that it decreases conduction. Na+ channels are across the axonal membrane in unmyelinated neurons and in myelinated neurons, it is present only at the gap( called nodes of ranvier) where myelination is absent. All the Na+ channels need to be activated in case of unmyelinated neurons while Na+ channels at only one place needs activation called Axon hillock.

In unmyelinated neurons, generation of action potential is more difficult compare to myelinated neurons.

The Mutation in K+ ion channels also slowed it's activity. K+ is responsible for repolarisation. Mutation slowed the repolarisation and makes the cell depolarised for long time.