Your question is not complete. There is not enough information. What are you referring to as "they". Some nerve fibers have thick myelin sheaths and some don't.
large teeth,super thick skin, swim well, can go on land, and did i mention LARGE teeth?
Large, pale white---and they are larger than chicken eggs and have thick shells
It is the skin of the rhino that is 5 cm thick. The skin of the rhino and hippopotamus is usually between 1.5cm and 5cm thick.
elephant- (describes a large mammal with thick, almost hairless skin, a long, flexible, prehensile trunk, upper incisors forming long curved tusks of ivory, and, in the African species, large fan-shaped ears) -iasis (process or resulting condition)
lipizzaners are solid black when they are born up to about 2 years old. then their coat starts to change to a solid pure white and that is how they stay the rest of their life. lipizzaners had strong back legs, large chest, thick neck and a large thick head. they often stand around 15-16 hands high.
thick
A large flat often thick piece of comething
Cells of the pith of a stem generally have thick cell wall and large vacuoles. Likewise, cells of the cortex in the older parts have thick cell wall and large vacuoles.
0.006
large fields and thick forrests.
A "thick booty" is considered to be rather large in size but still toned, round and sexy. Fat and or "fluffy" do not have the same equivalency as "thick".
A large thick mass of ice that moves is an Iceberg.
a glacier
Jupiter
polar bear
a chair
Pachyderm - pachy means "thick" and derm means "skin".