Final answer:
Mechanoreceptors have a lower threshold than nociceptive fibres because they are sensitive to gentle touch, unlike nociceptors which respond to potentially damaging stimuli signaling pain.
Step-by-step explanation:
Mechanoreceptors have a lower threshold than nociceptive fibres because they are designed to respond to light, mechanical stimuli such as touch, pressure, and vibration, rather than to the potentially damaging stimuli that activate nociceptors. Mechanoreceptors, like Merkel's disks and Meissner's corpuscles, are small, finely calibrated, and located in the upper layers of the skin to precisely localize gentle touch. On the other hand, nociceptors are responsible for the sensation of pain and are activated by mechanical, chemical, or thermal stimuli that exceed a certain threshold level, indicating potential damage.