mechanosensation and pain Flashcards
what are the five types of touch receptors
pacinian copuscle
meissners corpuscle
merkels disc
ruffinis ending
free nerve ending
what type of touch receptor is with various touch and pressure and pain and temp
free nerve endings
epedermis
type of touch receptor for steady pressure, texture, slow adapting
merkels disc
epedermis
small and sharp borders
type of receptor for stroking and flutter and is rapid
meissners corpuscle
dermis
type of receptor for vibration, and pressure and is rapid adapting
pacinian or lamellated copuscle
hypodermis
large and vague borders
type of receptor for stretch and is slow adapting
ruffinis ending
hypodermis
large and vague borders
what type of fibre is the pacinian corpuscle
Aa or AB fibre
pain
unpleasant sensory and emotional experience associated with or resembling that associated with actual or potential tissue damage
pain
unpleasant sensory and emotional experience associated with or resembling that associated with actual or potential tissue damagep
purpose of pain
protectice mech bring conscious awareness that tissue damage is occuring or about to occur
congenital analgesia
not feeling pain
mechanical receptors
respond to mechanical damage such as cutting, crushing, and pinching
thermal receptors
temp extremes
polymodal receptors
damaging stimuli
do nociceptors adapt
no
can nociceptors be sensitized
yes
peripheral: by prostaglandins (PGs)- enhance the receptor response to noxious stimuli
central; by NMDA receptor mediated long term potentiation
hyperalgesia and allodynia
what does aspirin and other NSAIDs do
inhibit synthesis of PGs- analgesic effect
fast pain
initial perception as brief, sharp sensation easily localized and originates from specific mechanical or thermal receptors followed by slow pain
slow pain
throbbing poorly localized and persistant feeling
contributes to the inflammatory respnse to tissue injury
perstance of chemicals leads to long lasting pain that coninues after removal of mechanical or thermal stimulus
what activates the slow pain pathway
chemicals like bradykinin or other PGs
PG
prostaglandins
what provokes pain
stimulating polymodal receptors
two afferent fibres that transmit pain to CNS
Ag and C fibres
Ag fibres
myelinated, medium sized, fast. cold, warmth, mechanical
C fibres
unmyelinated, smallest and slowest. heat, cold, mechanical
C fibres
unmyelinated, smallest and slowest. heat, cold, mechanical
Aa and AB fibres
myelinated and large
proprioception, light touch
pain neurotransmitters
substance P
Glutamate
substance p
activates ascending pathways that transmit nocicpetive signals to higher levels for further processing
glutamate
major excitatory neurotransmitter
binding to AMPA receptors leads to AP in dorsal horn neurons (sensitizing)
binding to NMDA receptrs inc ca entry and activates second messenger systems that make neurons more excitable. contributes to hypersenitivity and hyperlgesia in injured area
can chronic pain and pain sensitization occur in the absence of injury
yes
sensitization
pain percieved due to abnormal signallingn
hyperalgesia
lowered threshold to thermal or mech stimualtion- induced pain at the injured site (primary hyperalgesia)
allodynia
innocuous stimuli- touch- can result in a painful sensation due to sensitization of adjascent uninjured tissue (2nd hyperalgesia)
what is the main component for sensitizing procedure of the nociceptors
PG
what does glutumate process like
LTP- wind up- long term changes in synaptic transmission
what does the built in pain suppressing system involve
Periacqueductral grey matter- PAG- and reticular formation- stimulation of those leads to profound analgesia and blocks substance P release from afferent nerve termials (presynaptic inhibition)
endogenous opiates
endorphines, enkaphalins, dynorphin (runners high)
what does the pain descending system depend on
presence of opiate receptors released from the terminals of descending alalgesic pathway
opiates bind to opate receptrs on the presynaptic terminal of the primary sensory afferent which blocks further transmission of pain signal by presynaptic inhibition
tactile stimulation example
rubbing bumped elbow lessens pain
pain perception cognitive system
no pain, mild, excrutiating goes back to spinal chord processing
pain preception motivational affective system
tiring, fearful
pain perception sensory discriminative system
throbbing, shooting
