The vertebrate endoskeleton is internal while an arthropod's exoskeleton is not
C. Enzymes increase the rate of the chemical reactions carried out during metabolism.
A myelinated axon has a sheath around it and a bore axon doesn't have it, it's open or exposed so to speak. T<span>he myelin is made up of fat and protein and works like insulation. these axons make up the white matter in the brain since it appears white. The sheath helps to keep the electrical current from leaving the axon and the myelin sheath provides a tract along which regrowth can occur. </span>