Are sensory mechanoreceptors and mechanical nociceptors the same type of neurons or are they different?

Question

I always supposed the neurons / receptors which transmitted touch and pain were the same, since they react to stimulus which are the same but with different intensity, and they just sent a stronger signal in the case of something that has to be interpreted as pain. Though recently I've read some articles that imply they aren't, even so they don't say it directly. Reading more information I found this,

A nociceptor ("pain receptor") is a sensory neuron that responds to damaging or potentially damaging stimuli by sending “possible threat” signals.

Types and functions

Mechanical nociceptors respond to excess pressure or mechanical deformation.

Nociceptor

Then,

Are sensory receptors neurons?

Receptor cells are specialized neurons

Are sensory receptors neurons?

And finally,

Sensory receptors are primarily classified as chemoreceptors, thermoreceptors, mechanoreceptors, or photoreceptors.

Mechanoreceptors detect mechanical forces.

Sensory receptors

This doesnt give me a definitive answer, but it tells me both "sensory mechanoreceptors" and "mechanical nocireceptors" are neurons which responds to pressure/ mechanical forces. Are they supposed to be the same types of neurons named differently by different authors, or are they different types of neurons?

Answer 1

Short answer
Nociceptors are different from mechanoreceptors.

Background
Mechanoreceptors in the skin have specialized dendritic regions that facilitate their specific role in sensing different types of mechanical force, e.g., pressure receptors (Merkel’s disks) versus vibration receptors (Pacinian corpuscles and Meissner's corpuscles). See Fig. 1 for schematic representations of these types of receptors (Iheanacho et al). By contrast, pain receptors (or nociceptors) do not have specialized dendritic regions and consist of free nerve endings that respond to harmful mechanical forces (Purves et al., 2001).

^{Fig. 1. Skin receptors. source: Teach Me Phsyiology}

<sub>References
- Iheanacho et al., Mechanoreceptors. In: StatPearls. Treasure Island (FL): StatPearls Publishing (2020)
- Purves et al., eds. In: Neuroscience 2^nd ed. Sunderland (MA): Sinauer Associates; 2001. Nociceptors</sub>

Answer 2

I don't know if this directly answers your questions, but I think some confusion may stem from an underlying misconception of receptor vs receptor cell.

In most contexts (though not this one), 'receptors' do not refer to cells. Receptors are proteins on the cell membrane that transduct some signal/stimulus to the cell. Sometimes a "normal" peripheral neuron will have end processes that contain receptors that pass the signal directly to the neuron. Other times, a special 'receptor cell' is present. These cells are labeled as mechanoreceptors or nociceptors. The difference here is that a "standard" neuron is responsible for signal gating and propagation, whereas a receptor (cell) is primarily responsible for converting an external stimulus into a chemo or electrical signal recognized by "normal" neurons (or other cells).

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Edit: As noted by AliceD's answer, different receptors have different proteins and thus have different mechanisms. To add, "nociceptor" and "mechanoreceptor" are categories. There are many different receptors that are nociceptors and many different receptors that are mechanoreceptors. Furthermore, nociceptor is a category of 'function' - it describes that the receptor responds to a pain/damage stimulus. A mechanoreceptor is a category of 'mechanism' - it describes how the receptor works. These categories are not mutually exclusive, and there are indeed nociceptors that are ALSO mechanoreceptors. (E.g. "Joint nociceptors are classified as high threshold mechanoreceptors" (source)) But not all nociceptors are mechanoreceptors and not all mechanoreceptors are nociceptors.