- The conduction velocity of a nerve is determined mainly by the fibre diameter and the degree of myelination of nerve.
- Reduction in conduction velocity indicates injury to the nerve or some defects in the nerve.
Q.1 What are the factors that affect the velocity of
conduction in the nerve?
A. Species differences:
- Compared to mammals, the velocity is lower in amphibia.
B. Diameter of nerve fiber:
- The conduction velocity is about 5 m/μm diameter of the fiber.
C. Presence of myelin sheath:
- In myelinated fibers, the nerve impulse jumps from one node of Ranvier to the next, a process called saltatory (jumping) conduction. (Ionic fluxes occur only at the nodes).
D. Temperature:
- It also affects the conduction velocity, warming increasing it and cooling decreasing the velocity.
Q.2 What is the normal velocity of conduction of the Sciatic nerve of the Frog?
- The velocity of conduction in a nerve fiber having diameter of 12-20 µm range between 60 and 120 ms.