(a) Neuron — Neuron (nerve cells) are the fundamental units of the nervous system specialized to transmit information in the form of electrical impulses to different parts of the body.
(b) Nerve — Nerve is a bundle of nerve fibres (axons) of separate neurons, enclosed in a tubular sheath.
(c) Stimulus — An agent or the sudden change of the external or internal environment that results in a change in an organism or any of its body parts is called a stimulus.
(d) Synaptic cleft — The gaps between the axon terminals and the dendrites of another one or more neurons are called synaptic clefts.
(e) Reflex action — Reflex action is an automatic or quick or immediate involuntary action in the body brought about by a stimulus.
(f) Corpus callosum — Corpus callosum is a sheet of fibres connecting the two cerebral hemispheres.