Lecture 3- Skin Physiology Flashcards
Skin Physiology
What are the skin receptors?
draw
Free Nerve Endings Tactile Discs Tactile (Meissner) Corpuscles Lamellar (Pacinian) Corpuscles Bulbous (Ruffini) Corpuscles
What are Free Nerve endings?
Most common receptor in the skin.
Sensory axon branches and the terminals extends into epidermis.
Sensory terminals have receptors eg TRPV1 (cation channel).
What do receptors (TRPV1) do when the nerve terminal is stimulated (free nerve endings receptors)?
Receptors act as an ion channel and can open and allow cations (sodium and calcium) to come into the sensory terminal, depolarise it and action potentials can be conducted up to the somatosensory cortex, and become aware of the sensation.
what do free nerve endings consist of (2 categories)?
C fibres - small diametre and unmyelinated (conducts slowly 2ms-1)
Aδ (A delta) - slightly larger and myelinated (conduct impulses quicker 5-30ms-1)
Free nerve endings - RESPONDS TO
Temperature (hot / cold)
Painful stimulus
some movement and pressure
Histamine receptors - Itch (mosquito)
Peritrichial endings
Tactile (Merkel) discs (location, Abundant in)
Stratum basale epidermis
Fingertips and very small receptive fields. good for 2 point discrimination.
Peritrichial ending
nerve ending Wrapped around Hair follicles acts as
light touch receptors which detect bending of hairs eg when mosquito lands on skin.
Tactile (Merkel) discs responds to
objects physical features
texture, shape, edges
fine touch and light pressure
Tactile (merkel) discs are associated with large disc shaped…
Epidermal (merkel) cells, where communication between the tactile epithelial cell and nerve ending possibly serotonergic (5HT)
Tactile (Meissner) Corpuscles location (incl examples)
Papillary layer of dermis
Hairless skin, finger pads, eyelids, lips, external genitalia, sole of feet, nipples
Tactile (Meissner) Corpuscles structure (myelinated?, capsule, ions, what does deformation of capsule trigger?)
- Spiralling / branching unmyelinated sensory terminals surrounded by schwann cells and by a thin oval fibrous connective tissue capsule.
- Deformation of capsule triggers entry of Na+ ions in nerve terminal, releases APs
Tactile (Meissner) Corpuscles responds to
- Delicate fine, discriminative touch.
eg Shape & textural changes, reading braille text.
Movement of objects over surface of skin. - Light pressure
- Low frequency vibration (2 - 80 Hertz)
Lamellar (Pacinian) Corpuscles location
Scattered deep in dermis and Hypodermis (can be found in waide variety of other organs)
Lamellar (Pacinian) Corpuscles structure
Single dendrite lying within concentric layers of collagen fibres and fibroblasts
- Layers separated by Interstitial fluid (Gelatinous)
- Dendrite isolated from stimuli other deep pressure
Lamellar (Pacinian) Corpuscles - Deformation of capsule opens…
pressure sensitive Na+ channels in axon
- Inner layers covering axon terminal ‘relax’ quickly so APs discontinued.