CBSE Class 9 Answered

Nerve impulse is the message or information in the form of an electrochemical signal that travels through a neuron in response to a stimulus. It is accompanied by a transient change in electric potential in the membrane of the nerve fiber.

Impulse is the means by which information is transmitted in the nervous system from one neuron to another, or from a neuron to an effector organ (e.g. a group of muscle fibres). A nerve impulse takes the form of a wave of depolarisation, which passes along a nerve fibre. During its passage, the resting potential of the neurone is reversed and becomes an action potential.