3.2 Touch and Pain Flashcards
Touch
largest sensory system
most complex sense
ALL about survival
proprioperception
awareness of own body breaks into 4 categories: 1. temperature 2. kinaesthetic (muscles) 3. vestibular (motion) 4. Pain
Skin
stimulus area for touch but varies depending (ie: pressure, damage, temp, etc)
Hairy Skin
Main skin
Epidermis (outer): Dead cells
Dermis (middle): makes new cells
Hypodermis (subcutaneous): contains nerve endings
glabrous skin
non hairy skin
palms, sole etc
thicker outer layer
more complex receptors (as its how we explore the world)
Receptor types
free nerve endings and encapsulated endings
differences in shape, size, organization (suggests functional specialization)
Specificity theory on skin sense
each receptor is responsive to one type of stimulus. evidence suggests this isn’t true
pattern theory on skin sense
pattern of nerve impulses determines sensation (coding)
Melzack and Wall Theory
blended theory of skin
each receptor can convert particular kind of stimulus into particular types of impulses
hard to support for/ find evidence
- Response to wide variety of stimulus
- Responds as much to Dif stimulus but in Dif patterns
touch pathways
starts at skin then splits into two Dif systems at spinal cord: spinothalamic and lemniscal
both end up in somatosensory cortex
contralateral connection
spinothalamic pathway
pain pathway
small nerve fibres
poor localization
lemniscal pathway
large/fast nerve fibres
precise localization
touch
pressure on skin
several difference receptors
types of touch receptors
pacinian corpuscles, Rapidly adapting, and 2 slow adapting
Pacinian corpuscles
encapsulated nerve ending
onion-like: 70 layers
sensitive to changes in stimulation but not good with sustained
ONSET/OFFSET sensitivity
Rapid adapting and one slow adapting
small receptive field with distanct borders
pacinian corpuscles and one slow adapting
large receptive field with non-distinct borders
threshold for touch
homunculus (more space in brain = greater sensitivity)
passive touch
placing object on skin
absolute threshold: smallest detectable
Studied using: von frey hairs (experiment by Weinstein showed women were more sensitive to touch)
Most sensitive: soles of feet
Least sensitive: calf
two point discrimination threshold
how to measure threshold of passive touch
Measuring ability to notice 2 points are 2 points (pull them further and further apart from eachother)
active touch
exploring through touch
Haptic perception: ID through touch
assess lateralization of function (dichhaptic stimulation)_
generally a lower threshold than passive
lateralization of function studied through touch
touch with right hand: verbal ID (Left hemisphere)
touch with left hand: functional ID (right hemisphere)
TOUCH ADAPTATION
NOT DUE TO FATIGUE in RA + PC (better with onset offset)
it is due to fatigue in Sa
Pain phenomena
perception of tissue damage
sensory and EMOTIONAL component
internal stimulation
threshold of pain
depends on senstiivty criterion and body part
pain points
more pain points means lower threshold (Higher sensitivity) and not related to absolute threshold
Pain tolerance
complicates the identification of thresholds
due to individual differences
pain adaptation
only mild
hot water up to 46 degrees
theories on pain perception
specificity: specific pain receptors
pattern theory: specific patterns of stimulation
ignores psychological aspects (emotion) and physiological (no pain receptor)
gate control theory of pain
pain is an interaction between neural fibres and the brain
Transmission cells: pain info sent to brain
Neural fibers: affect substantia gelatinosa (GATE)
large fibres stimulated = gate closed = perception of pain decreases
small fibres stimulated = gate open = perception of pain increases
Also controlled by descending inhibitory control (brain top down)
temperature sense
separate from touch
not mechanical pressure its about air temperature
cold air
blood vessels on surface shrink (vasoconstriction)
shivering
leads to body warming
warm air
blood vessels on surface get bigger (vasodialation)
and sweating
leads to body cooling
thresholds of temperature
different for cold and hot
cold spots and warm spots on skin
specificity theory of temperature
coded in nervous system by receptors similar to touch
warm: increases firing rate (to encourage cooling)
cold: decreases firing rate (to encourage warming)
absolute threshold of temp
none, only difference
because different areas on body have Dif sensitivity
warmth: forehead (least: arms, chest, shoulders)
cold: trunk (Least: arms, legs)
threshold of temp affected by:
size of area of skin exposed, current skin tem[, time of day, phase of menstrual cycle, stress
thermal adaptation
only mild temperatures
can adapt completely between 29 and 37
