Sensory receptors encode four types of information for the central nervous system:
1. modality - the stimulus experienced or felt. Recall all nerve impulses arrive at the brain and must be interpreted which often depends on the nerve fiber. Nerve impulses arriving on the optic nerve, even the pressure of rubbing the eyelids, are experienced as light.
thermoreceptors sense heat, cold
nociceptors sense pain
chemoreceptors sense smell, tastes
photoreceptors sense light
mechanoreceptors sense pressure, touch
2. direction or acuity of location - depends on specific nerve fibers. The brain uses sensory projection to finely pinpoint the area of a stimulus.
3. strength or intensity - a strong stimulus might use multiple nerve fibers to increase firing. A weak stimulus will employ sensitive nerve fibers and a strong stimulus will activate those plus higher threshold fibers.
4. duration - receptors demonstrate a decrease in firing frequency as the time of the stimulus goes on. They can adapt and change frequency.