An overview of the different structures detecting different sensations in the skin

1. C.Riedinger
Overview of somatosensory receptors
Receptive
Name Type Location Adaptation Task Afferent fibres
field
specialised
superficial
Meissner's corpuscle mechanoR small fast fine localisation of rapidly changing stimuli A-beta
(<keratin)
ending
specialised
deep (in fatty high frequency (300Hz) vibration
Pacinian corpuscle mechanoR large fast A-beta
layer) can't localise source
ending
specialised
superficial best at reading Braille
Merkel's disk mechanoR small slow A-beta
(<keratin) slowly moving stimulus
ending
specialised
deep (in fatty
Ruffini ending mechanoR large slow deep pressure A-beta
layer)
ending
free nerve
fires around 40*C
Hot temperature receptor ending, TRP slow AC
responds to capsaicin (chilli)
ion channels
free nerve
Cold temperature fires around 20*C
ending, TRP slow A-delta
receptor responds to menthol
ion channels
free nerve
Very cold temperature fires around 10*C
ending, TRP slow A-delta
receptor responds to isocyanates (wasabi)
ion channels
not specific=MULTIMODAL
respond to a wide range of ihigh threshold noxious
free nerve
Nociceptor sensitise!! (painful) stimuli, e.g. strong mechanical pressure, cold A-delta and AC
ending <15*C, heat >43*C, chemicals
sensitise to prolongued stimulus
embedded in group I=A-alpha
Proprioceptors muscle spindles
muscle fibres - fast detect the length of muscle (slow and fast
(muscle length) nuclear bag
1/1000 adapting)
embedded in
Proprioceptors muscle spindles group I and II=A-beta
muscle fibres - slow detect the length of muscle
(muscle length) nuclear chain (slow)
1/1000
Proprioceptors (stretch) tendons Ib (medium and fast)
in joint
Proprioceptors (joint) Ruffini type signal joint angle in extreme angles, not mid-way
capsule