The Telephone Wires That Lead from Your Home to the Homes

The telephone wires that lead from your home to the homes of friend,relatives,and even strangers are all covered by a thick,protective tube that insulates them from damage.This tube helps eliminate damage from things like water,birds' feet,bugs,dirt,weather,tree branches,and other potential interruptions in communication.In the human neuron,the same sort of protection is provided by the __________.

A) synaptic vesicles
B) dendrites
C) sodium ions
D) myelin sheath