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.
thin and moist, with a large surface area and a large concentration gradient.
Large, pale white---and they are larger than chicken eggs and have thick shells
Crocodiles have adaptations such as a streamlined body for efficient swimming, powerful jaws for catching and eating prey, webbed feet for swimming, and a thick skin for protection. They also have a valve in their throat that allows them to open their mouth underwater without letting water in.
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.
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.
large fields and thick forrests.
0.006
A large thick mass of ice that moves is an Iceberg.
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".
Jupiter
polar bear
Pachyderm - pachy means "thick" and derm means "skin".
Rhino
Something that has a large distance between its opposite sides or surfaces can be considered thick. Tend to be solid and not easily bent or broken.