In an answer provided by DavidCian, it is mentioned that thermoception is separate to the 5 human bodily senses (sight, hearing, touch, smell and taste). Yet, I would have thought it would be part of the sense of touch.

The Wikipedia link mentions that Ciliopathy is a loss of ability to sense heat. Does Ciliopathy prevent you from sensing touch? If not, maybe it is a separate sense after all?


Short answer
Heat receptors are often grouped under the 'skin receptors', and hence are bundled along with touch (pressure, vibration, stretch), cold and pain receptors.

However, ciliopathy is a disorder affecting some, but not all of the skin receptors, and affecting unrelated sensory modalities like vision and audition. This is because functionally, the receptors responsible for these different modalities include the same molecular cilia (hair)-like components.

Great question. The 5 most common 'basic' senses are the ones you listed, namely the visual, auditory, gustatory, olfactory and tactile, corresponding to the systems responsible for sensing and perceiving light, sound, taste, smell and temperature.

However, these are schoolbook examples and the list is more extensive. What about

  • The vestibular system that is responsible for perception of acceleration and gait?
  • Proprioception, mediated by muscle spindles that feedback muscle activity back to the brain to complete a closed loop system responsible for the perception of bodily position and location?
  • The sense of pain (nociception)?
  • And within the realm of touch, there is the perception of skin stretch, or the sense associated with the movement of hairs so important for animals like moles and nightly hunters that use them for navigation? Are vibratory receptors to be grouped with those sensing static pressure?

These examples can, however quite easily be categorized under the 'basic senses' by stretching the definitions a bit here and there. The vestibular system is often grouped into the auditory system, because 1) the perception of bodily rotation and acceleration is also sensed by fluid-bound hair cells, akin to the ones in the cochlea sensing acoustic waves and 2) because the end organs of the vestibular system are located in the inner ear and actually coupled to the cochlea. It harbors different receptor cells responsible for sensing acceleration or bodily rotation.

Pain, stretch, hair, vibration and pressure receptors are all grouped into the 'skin receptors', and often clustered under the group 'touch'. Muscle spindles, though are quite special and very difficult to cluster into anything, because they functionally systemwide into the sense of balance, yet their function is more like a sense of touch.

Thermoception is thus bunched into the group of skin receptors. However, vibration, static pressure, hair movement, pain, heat and stretch are all sensed by different receptor cells with different afferents to the brain and many subtypes exist within these groups, such as fibers mediating pain swiftly ('sharp pains'), or slowly (associated with 'chronic pain' and very responsive to opiates) and vibration receptors that adapt swiftly or more sluggishly etc etc.Thermnoception itself is mediated via receptors sensing 'cold' (sensitive to menthol) and 'heat' (sensitive to capsaicin in peppers).

Concerning cioliopathy, you can see in your linked web page that associated comorbidities include sensorineural hearing loss; hair cells also have cilia that are responsible for detecting movement. Here you can see how difficult classification is; apparently, functionally, pain receptors can be classified into the same group as balance and sound detectors, and even retinal cells seeing the web page you linked. However, their sensory modalities are entirely different. The groupings discussed above are mostly from a sensory modality point of view.


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