A blue whale (Balaenoptera musculus) has motor neurones that can be up to 25 metres in length, extending from the spinal cord to the tail flukes. In contrast, the interneurones (relay neurones) within the whale's cerebral cortex are highly concentrated and very short.
Explain why myelination is vital for the motor neurones innervating the tail flukes but is less critical for the interneurones in the cerebral cortex.