Skin and Nervous System: A Bidirectional Partnership

The skin and nervous system are embryologically linked (both from ectoderm) and maintain lifelong bidirectional communication.

Sensory Functions (Skin → Nervous System)

• Mechanoreceptors: Merkel (pressure), Meissner (light touch), Ruffini (stretch), Pacinian (vibration).
• Thermoreceptors: TRP channels detect heat (TRPV1) and cold (TRPM8).
• Nociceptors: Pain from thermal, mechanical, chemical stimuli.
• Itch (Pruriceptors): Histamine-dependent and -independent pathways.

Signals travel via dorsal root ganglia → spinal cord → thalamus → somatosensory cortex.

Motor/Autonomic Functions (Nervous System → Skin)

• Vasomotor: Sympathetic tone controls cutaneous blood flow (thermoregulation, blushing, pallor).
• Sudomotor: Sympathetic cholinergic fibers activate sweat glands (thermoregulation, emotional sweating).
• Pilomotor: Sympathetic → arrector pili muscles → goosebumps.
• Trophic: Neuropeptides (substance P, CGRP, NGF) maintain epidermal integrity, barrier function, immune modulation.

Wound Healing & Neuroimmune Crosstalk

• Nerves release neuropeptides promoting angiogenesis, keratinocyte migration, immune cell recruitment.
• Denervated skin heals poorly (neurotrophic ulcers).
• Skin immune cells (Langerhans, mast cells) communicate with nerve endings.

Clinical Examples

• Herpes zoster: viral reactivation in dorsal root ganglion → dermatomal rash/pain.
• Complex Regional Pain Syndrome: autonomic/sensory dysregulation after injury.
• Neuropathic itch: nerve injury → central sensitization.

The skin is a neuroimmune sensory organ, not just a barrier.