Pain sensation arises in free nerve endings called what?

Pain sensation is primarily detected by specialized sensory receptors known as nociceptors. These receptors are a type of free nerve ending that respond to potentially harmful stimuli, including mechanical, thermal, or chemical changes that can cause tissue damage. When activated, nociceptors send signals through the nervous system to the brain, resulting in the perception of pain.

The other receptor types mentioned serve different functions. Thermoreceptors are sensitive to temperature changes, mechanoreceptors respond to mechanical pressure or distortion, and proprioceptors provide information about body position and movement. Therefore, nociceptors are uniquely suited to detect and transmit pain sensations, making them the correct answer to the question.