wk 10 SP Flashcards
Area and weight of skin
1.82 m^2
Weight 5kg
- Two types of skin
Glabrous – palms of hands and feet
Hairy – everywhere else
4 senses in skin
touch (mechanical )
pain
temperature
body sense (proprioception)
4 different tactile receptors in skin
Merkel’s disc
Meissner corpsucle
Ruffini organ
Paccinian corpuscle
Merkel’s disc
responds to what
Fine details e.g. braille
Meissner corpuscle responds to what
Flutter (e.g. objects slipping through fingers)
Ruffini organ responds to what
stretching (due to picking up something)
Paccinian corpuscle responds to
vibration, fine texture
Receptive fields…
The area of skin
that a particular
cell receives
information about
Paccinian corpuscles have
_______ receptive fields than Meissner’s corpuscles
larger
Active touch –
active exploration of environment
Passive touch
– body is stationary
Advantages of active touch
More parts of body contact object
* You can search for the most diagnostic
parts of objects to feel
* Kinesthetic senses are also engaged
different cues when percieving texture
Spatial cues – bumps and grooves, when finger is stationery or moving
- Temporal cues – only when move finger across surface
– Paccinican corpuscles – adaptation to high frequencies impairs performance
– Can perceive texture via a tool
evidence that there is a difference between recognising an object through touch and recognising where the object is via touch
brain imaging shows
activity in primary and secondary somatosensory cortex when asked WHAT object was
activity in superior parietal areas when asked WHERE object was
Top down influences on touch
must update as move body position
Emotional effect - e.g. same sensation may be pleasant or unpleasant depending
Expectation - e.g. surprise tickling
pain receptors called
nociereceptor
2 types of pain
fast pain , slow pain
same stimulus can activate both systems
A delta fibres (type of pain)
fast pain (sharp)
pin prick, pinches, extreme temperature
are myelinated
C fibres (type of pain)
slow pain (dull) - many types of pain,
even mild stimulation can be pleasurable
not myelinated
pain is more than receptor activity e.g can be affected by
a mental state e.g. battlefield analgesia
Occour in absence of stimulation e.g. phantom limb pain
be affected by attention
Gating of pain in the spinal chord influences degree to which painful info reaches the brain,
pain can be reduced by
non-painful tactile inputs e.g. massage, rubbing
Top down input, expectations
Proprioception
Where your body is in space
- Signals from muscles
Also can use other modalities – vestibular system, tactile receptors etc.
Also Kinesthesis – movement of the limbs in space
A new receptor discovered in
2002
- Patient like Ian
Waterman - Lost other senses of
touch - Could still feel pain,
temperature and enjoy
being cuddled - CT (C Tactile)
