Cutaneous Senses: Receptors & Modalities

Cutaneous Sensory Modalities & Receptors

Modality	Primary Receptor(s)	Fiber Type	Notes
Light Touch	Meissner's corpuscles, Merkel cells	Aβ	Texture, low-frequency vibrations
Pressure / Deep Touch	Ruffini endings, Pacinian corpuscles	Aβ	Sustained pressure, stretch
Vibration	Pacinian corpuscles (high freq), Meissner's (low freq)	Aβ	Pacinian: 200–300 Hz optimal
Temperature – Cold	TRPM8 (C-fibers, Aδ)	C, Aδ	Innocuous cool to noxious cold
Temperature – Heat	TRPV1, TRPV3, TRPV4 (C, Aδ)	C, Aδ	Innocuous warm to noxious heat
Pain (Nociception)	Free nerve endings (TRPV1, ASIC, P2X)	Aδ (fast, sharp), C (slow, dull)	Mechanical, thermal, chemical
Itch (Pruriception)	Subset of C-fibers (Mrgrpr, GRPR)	C	Histaminergic & non-histaminergic
Proprioception (Joint Position)	Muscle spindles, Golgi tendon organs, joint capsules	Ia, II, Ib	Conscious & unconscious
Kinesthesia (Movement Sense)	Muscle spindles, joint receptors	Ia, II	Direction, velocity, force

Pathways

• Dorsal Column-Medial Lemniscus: Fine touch, vibration, proprioception → contralateral thalamus (VPL) → sensory cortex.
• Spinothalamic Tract: Pain, temperature, crude touch → contralateral thalamus → cortex.
• Spinocerebellar Tracts: Unconscious proprioception → cerebellum.