The four different types of general sensory receptors include mechanoreceptors, thermoreceptors, chemoreceptors and nociceptors. Mechanoreceptors, thermoreceptors and nociceptors are categorized as somatosensory receptors responsive to mechanical displacement, temperature and pain, respectively, while chemoreceptors respond to chemical stimuli. Receptors respond to multiple stimuli and are therefore categorized by their lowest threshold.
Mechanoreceptors respond to a wide array of external and internal stimuli, such as touch, pressure, stretching, movement, itching and vibration. They function by sending signals to the central nervous system when their membranes are displaced. These can be further grouped into three smaller categories by what causes their signal transmissions: position and velocity receptors, velocity receptors and transient receptors.
Thermoreceptors detect temperature within and outside of the body. Externally, warm receptors and cold receptors detect temperature increases and decreases within the range of 59 to 109 degrees Fahrenheit. Nociceptors recognize pain associated with extreme mechanical, temperature and chemical stimulation.
External chemoreceptors concern taste and smell, and internal chemoreceptors monitor blood chemistry in the carotid body, aorta and brainstem. Taste receptors in the taste buds and smell receptors in the olfactory epithelium are closely linked and activated by similar stimuli. Messages to the brain from internal chemoreceptors do not result in a conscious sensation.