Question

The impulses travel faster when _________

(a) the axon has myelin sheath

(b) the axon does not have myelin sheath

(c) the cyton is small

(d) the dendrites are longer

I got this question in homework.

My question is based upon Nerve Conduction Velocity topic in chapter Diagnostic Investigation in Neurology and Cardiology of Clinical Science

Answer 1

Correct option is (a) the axon has myelin sheath

Easiest explanation: Myelin sheath is a sheath of fats covering the length of the axon with small breaks between them called the Nodes of Ranvir. Since the sheath is made of fats and fats are insulators, the impulses cannot travel in them. In a absence of myelin sheath, the impulses would have moved by depolarizing the adjacent point. However, since the fats of myelin sheath are blocking it, the impulses move by jumping between the Nodes of Ranvir. This increases the speed of conduction.