Sensory receptors can be classified based on the type of stimuli to which they respond.
- Mechanoreceptors respond to mechanical stimuli such as tension (stretching) or pressure. They tranduce mechanical energy into nerve impulses.
- Thermoreceptors respond to changes in temperature (heat and cold); they tranduce heat energy into nerve impulses.
- Nociceptors respond to injurious or painful stimuli; they tranduce a variety of forms of energy into nerve impulses.
- Photoreceptors respond to electromagnetic radiation, typically wavelengths of visible light, they tranduce light energy into nerve impulses; in humans (and most vertebrates), these are the rods and cones of the eyes.
- Chemoreceptor responds to chemical stimuli; they tranduce the binding of specific hemicals into nerve impulses; includes exteroceptors for smell and taste and interoceptors sensitive to concentration changes of some molecules in the blood.