Final answer:
Option (A), The nerve endings that sense fine touch initiating the DCML pathway are Meissner corpuscles, Pacinian corpuscles, Ruffini endings, and Merkel complexes.
Step-by-step explanation:
The correct answer to the question regarding the 4 nerve endings or receptors that sense fine touch and thereby initiate the Dorsal Column-Medial Lemniscus (DCML) pathway is: Meissner corpuscles, Pacinian corpuscles, Ruffini endings, and Merkel complexes. These mechanoreceptors are essential for detecting various forms of tactile stimuli such as light touch, vibration, and pressure:
- Merkel complexes (also referred to as Merkel's disks) are slowly adapting, unencapsulated receptors that respond to light touch and texture.
- Meissner corpuscles are rapidly adapting, encapsulated receptors found in glabrous skin that respond to touch, low-frequency vibration, and flutter.
- Pacinian corpuscles are encapsulated, rapidly adapting receptors that detect deep pressure and high-frequency vibrations.
- Ruffini endings are slowly adapting, encapsulated receptors that detect skin stretch, joint activity, and warm temperatures.
Collectively, these receptors enable the perception of fine touch and are instrumental in the DCML pathway, where signals are transmitted from peripheral areas through the dorsal columns of the spinal cord to the brain.