Sensory Systems Flashcards
What type of nerve endings does information from pain and cold temperatures have?
Free nerve endings
What type of nerve endings does information from mechanoreceptors have?
Tactile nerve endings
What is the receptive field?
Responding to a stimuli over a specific area
What type of information and nerve endings does meissners and Merkel’s corpuscles have/recieve?
Both are tactile free nerve endings
contains information from tough - merkels
Contain information from light touch - meissner’s
What type of nerve ending is warmth and cold temperatures associated with?
Warmth = ruffini corpuscle Cold = free nerve ending (nociceptor)
Is activation of the receptor (generator) potential stimulated by hyperpolarisation or depolarisation?
Depolarisation
regarding signal transduction, what determines the intensity of the stimulus?
the size of receptor potential which evokes firing of action potentials thus the frequency of action potentials
regarding signal transduction what determines the location of the stimulus?
the receptive field
regarding signal transduction, what determines acuity?
the density of innervation and size of receptive field
cutaneous sensation is mediated by what 3 types of primary afferent fibres?
A beta = large myelinated
A delta = small myelinated
C = unmyelinated
what type of stimulus does the 3 types of primary afferent fibres receive?
A beta = touch, pressure, vibration
A delta =cold, ‘fast pain’, pressure
C = warmth, ‘slow pain’
what type of fibres is proprioception mediated by?
Aalpha
A beta
what type of fibres are thermoreceptors and nociceptors?
Adelta & C fibres
what type of fibres are mechanoreceptors?
Aalpha & Abeta
where does mechanoreceptors synapse and what type of fibres do they carry?
Aalpha and Abeta fibres
synapse in the cuneate and gracile nuclei in brainstem
where type of fibres does thermoreceptors and nociceptors carry and where do they synapse?
Adelta & C fibres
they synapse in the dorsal horn at point of entry
what receptors are Aalpha fibres?
mechanoreceptors
proprioceptors
what receptors are Abeta fibres?
mechanoreceptors
proprioceptors
what receptors carry Adelta fibres?
nociceptors and thermoreceptors
what fibres are unmyelinated and what receptors are they found in?
C fibres in nociceptors and thermoreceptors
what would result if there was damage to the dorsal columns?
loss of touch, vibration, proprioception below lesion on ipsilateral side
what would result if there was damage of the anterolateral quadrant?
loss of nociceptive and temperature sensation below lesion on contralateral side
what horn does the nociceptor and thermoreceptor fibres travel up through the spinal cord in?
anterolateral tract
what horn does the mechanoreceptor fibres travel up through the spinal cord in?
dorsal horn
what is adaptation?
after there is a constant stimulus the mechanoreceptors get used to it so the firing of action potentials decreases - you get used to the senstion so you don’t feel it i.e. putting a hat on
regarding processing in sensory pathways, what is referred pain an example of?
convergence
multiple incoming mechanoreceptors synapse onto 1 neurone
what is responsible for sharpening up stimuli?
lateral inhibition
neurones inhibit nearby neurones so the information being sent to the cortex is more accurate by giving better definition of boundaries
what is signal transduction in nociceptors activated by?
heat
low PH
local chemical mediators i.e. bradykinin, prostaglandins, histamine
describe the gate control theory.
when mechanoreceptor information enters the dorsal horn, it also gives off an interneurone which releases opioid peptides that inhibits transmitter release from nociceptor fibres heme closing the gate
what does NSAIDs inhibit?
cyclo-oxygenase
how does NSAIDS work?
they inhibit cycle-oxygenase which converts arachidonic acid to prostaglandins (prostaglandins produce inflammation)
therefore by inhibiting prostaglandin production you decrease the inflammation
how does local anaesthetics work?
they block all Na action potentials and therefore all axonal transmission
what are the 3 ways in which opiates work?
reduce sensitivity of nociceptors to bradykinin
block transmitter release in dorsal horn
activate descending inhibitory pathways
