Explain the properties of nerve fibre with reference to : (a) Irritability (b) Conductivity

Answer:

(a) Irritability (excitability): It is the ability of a nerve fibre to respond to a stimulus by generating an electrical impulse. When a stimulus of threshold strength or more is applied, the polarized membrane (resting potential about −70 mV) becomes depolarized and an action potential (nerve impulse) is produced.

(b) Conductivity: It is the ability of a nerve fibre to transmit the impulse along its length. The action potential at one point depolarizes the next part of the membrane, so the wave of depolarization travels along the fibre; in myelinated fibres it jumps from one node of Ranvier to the next (saltatory conduction), which is faster.