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How do mechanical stimuli activate pain receptors?

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How does the human body perceive and respond to pain? — pain Learn how the human body senses pain and reacts to it.

Mechanical stimuli activate pain receptors—specifically specialized nerve endings known as nociceptors—through the physical deformation of the nerve cell membrane. When these receptors are subjected to intense or harmful mechanical force, the resulting deformation induces electrical changes, known as receptor or generator potentials, at the cell surface. This process triggers the generation of nerve impulses (spikes) that are transmitted along afferent nerve fibers to the spinal cord and eventually the brain.12

It is important to clarify that not all mechanoreceptors are pain receptors; many are dedicated solely to reporting touch, pressure, or posture and do not produce pain regardless of the intensity of the stimulus. Pain-specific responses to mechanical stimuli are mediated by distinct, smaller nerve fibers, including:3

A delta fibres: Larger, myelinated fibers that conduct impulses rapidly, associated with the initial, sharp, and well-localized sensation of pain.1
C fibres: Smaller, unmyelinated fibers that conduct more slowly, associated with the lingering, poorly localized pain that follows the initial sensation.1

In the viscera, however, the mechanism can differ, as some pain may result from the summation of impulses in fibers that also report non-painful states like distension.3