Somatosensory 1 Flashcards
What are low-threshold units?
respons to low intensity stimuli (non-damagin and non painful)
What other name are high threshold units known by»
nociceptors
What is adaptation?
a feature of primary sensory neurones that determines whether they change their firing rate only in response to a stimulus of chagning intensity or fire continuously throughout a constant stimulus
What is a slowly adapting response?
continous information to CNS hile terminal deformed
What type of information do slowly adapting responses give?
position, degree of stretch of force eg stretch receptors
What are rapidly adapting responses?
detects changes in stimulus strength, the number of impulses is proportional to the rate of change of stimulus
Give examples of rapidly acting afferents?
some muscle spindles and hair follicle afferents
What are very rapidly adapting responses?
responds only to very fast movemnt such as rpid vibration
Give an example of a rvery rapidly adapting responses?
pacinian copuscle
What type of axon have the thickest myelination?
group 1/ Aa fibres
What type of modality are group 1/Aa fibres?
proprioceptors of SK muscle
What modality are group II or Ab fibres?
mechanoreceptors of skin
What modality are group III or Ad fibres?
pain and temperature
What modality are group IV or C fibres?
temperature, pain and itch
What is the receptive field of an afferent neurone?
the region that when stimulate with an adequate stimulus causes a response in that neurone
What is the relationship with discriminative capacity and receptive field?
regions with the highest discriminative capacity have the smallest receptive fields
What modality do free nerve endings carry?
pain, heat and cold
Where are Meissner’s corpuscles found?
in skin location where two point discrimination is highest, not in hairy skin
What modality do Meissner’s corpuscles carry?
touch- stroking,flutter
What modality do Merkel’s discs carry?
touch- pressure and texture
Where are Merkel’s discs found?
abundant where two point discrimination is highest, some in hairy skin
How are Merkel’s discs often grouped?
in Iggo domes
Where are Krause end bulbs found?
at the border of dry skin and mucous membranes
What modality do Krause end bulbds carry?
touch
Where are Ruffini endings found?
within dermis and joint capsules
What modality do Riffini endings carry?
pressure- skin stretch
Where are Pacinian corpuscles found?
within dermis and fascia
What modality do Pacinian cospuscles carry?
vibration
What modality do C mechanoreceptors carry?
stroking, social and erotic touch
What is the adaption of Meissner’s corpuscles?
RA
What is the adaption of Merkel disc receptors?
SA
What is the adaption of Pacinian corpsucles?
very RA
What is the adaption of Ruffini endings?
SA
What is the receptive field of Pacinian corpuslces compared to Meissners corpuslces?
Meissner’s corpuscles have much smaller RFs than pacinian cospuscles
What nerve group has a similar RF to Pacinian corpuscles?
Ruffini endings
What nerve group has a similar RF to Meissner’s corpuscles?
Merkel disc
Where are free nerve endings found?
epidermis
What is the fibre class of nociceptors?
Ad/C
What is the fibre class of low threshold mechanoreceptors?
Ab
What is the fibre class of proprioceptors?
Aa
Where is the termination of nociceptors in the dorsal horn?
laminae I and II
Where is the termination of LTMs in the dorsal horn?
laminae III to VI
Where is the termination of proprioceptors in the dorsal horn?
laminae VII to IX
