Stimulus is recieved by a nerve cell and the impulse is carried to the brain in the form of electric impulse induced by micro chemical reactions in the nerve cells and their network....the brain sends the response in the smae manner via another nerve cell to the area of reaction....In reflex actions, the messages and actions happen in the same manner except for the fact that it is conveyed to the spinal cord and the spinal cord send the response...
The nervous system is a network of cells called neurons which transmit information in the form of electrical signals. Your brain has around 100 billion neurons, and each communicates with thousands of others – as many connections as in the world's telephone system, the biggest machine on the planet. Neurons communicate with each other at special junctions where chemicals help to bridge the gap between one neuron and the next.