Q. Distinguish among the terms stimulus, sensation, and perception?

A stimulus is an energy source (chemical, light wave, pressure etc.) which activates a receptor cell (specialized nerve cell) to transmit a nerve impulse or sensation. If sensation arrives in conscious part of the brain, cerebral cortex, a perception occurs. Perception is awareness of stimulus. Pricking one's finger, for illustration is a stimulus which activates many receptor cells to send nerve impulses to the brain. Once these sensations reach cerebral cortex, a person perceives (feels) pain