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Dermatology
Cutaneous Neurophysiology
Built from Dermatology, 5th Edition
What’s inside
6 sections · 87 slides
Overview
- What this topic covers
- Itch is not just “mild pain”
Pruritus Pathways
How an itch signal travels from skin to spinal cord to brain
- Sensory nerve fiber types in the skin
- Primary afferent neurons that innervate the skin
- Primary afferent neurons that innervate the skin (continued)
- Two separate types of itch-carrying C fiber
- Cowhage pods, the source of the itch-provoking spicule mucunain
- How cowhage triggers itch
- Three subtypes of pruriceptive C neuron
- The spinal cord's itch relay
- Neuroanatomy of itch: from skin to spinal cord to brain
- Where in the brain itch is processed
- Contagious itch and the itch-scratch cycle
- Pruritus receptor units in the epidermis
Mediators of Pruritus
The chemical messengers that switch itch nerves on
- A whole cast of chemical itch triggers
- Histamine, the classic itch mediator
- Gastrin-releasing peptide and B-type natriuretic peptide
- Proteases: tryptase, kallikreins, cathepsins
- Mast cells and protease-driven itch, close up
- Opioid peptides and central itch
- Substance P
- Neurotrophins and nerve sprouting
- Dorsal root ganglia: home of the itch-sensing neuron
- Dorsal root ganglion: cell bodies of sensory neurons
- Prostanoids and leukotrienes
- TRP ion channels: the itch “thermostats”
- TRPV1 activation and itch signal transmission
- Other neurotransmitters and mediators
- Immune cells talk directly to itch nerves
- IL-31, OSMR, and a genetic itch disease
- Relative potency of itch mediators
- Major mediators of pruritus: relative potencies for pruritus and pain
- Major mediators of pruritus: relative potencies for pruritus and pain (continued)
- Mouse models confirm each mediator's role
- Murine models of itch
- Murine models of itch (continued)
- Murine models of itch (continued)
- Murine models of itch (continued)
- How a mediator becomes an itch signal
Chronic Itch
Why long-standing itch behaves differently from a single episode
- Chronic itch shares features with chronic pain
- Peripheral sensitization in chronic itch
- Central sensitization: alloknesis and hyperknesis
- Chronic itch versus chronic pain
- Comparison of characteristics of chronic itch and chronic pain
- Comparison of characteristics of chronic itch and chronic pain (continued)
- Mechanisms of itch sensitization in chronic pruritus
- Itch related to a damaged skin barrier
- Itch in older adults
- Cholestatic pruritus
Treatments for Pruritus
Turning knowledge of itch mediators into working drugs
- Why itch is harder to treat than pain
- Topical treatments: what they target
- Systemic treatments: what they target
- Drug treatment of pruritus
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- Drug treatment of pruritus (continued)
- A few more treatment notes
Future Directions
Where itch research is heading next
- Where itch research is headed
- Key takeaways
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Dermatology, 5th Edition (2-Volume Set)