Any stimulus is a form of energy, so when some energy applied in the form of stimuli, this causes change in membrane potentials of neurons innervating that region, and causes depolarisation, which results in impulse generation and transmission.
Depend upon the severity of stimuli, the duration of impulse varies. These senses are received by sensory receptors. These receptors transduce the stimuli and send signals to the CNS. All the sensory pathways involves four basic functions namely, sensory reception and transduction, transmission, perception, amplification.
Any sense received by an individual is only an approximate estimation of what is present. The perception of the world by any animal depends upon the information transmitted to the brain. Thus, “perception is not reality.”