sensory transduction Flashcards
what is a graded potential
Get cell to threshold so it can fire action potentials
a beta fibres
large myelinated- touch, pressure, vibration
a delta fibres
small myelinated- cold, fast pain and pressure
c fibres
unmyelinated- slow pain and warmth
what fibres is propioception stimulated by
A alpha and A beta
mechanoreceptors
project up through ipsilateral dorsal columns
synapse in cuneate and gracile nuclei
2nd order fibres corss over midline in brainstem and project to reticular formation
where do thermorecceptors and nociceptors synapse
dorsal horn
2nd order fibres cross over at midline
project up through lateral spinothalamic tract
how do NSAIDS work
prostaglandin sensitise nociceptors to bradykinin
inhibit cyclo-oxygenase which converts arachidonic acid to postaglandins
how do local anesthetics work
block sodium action potential and therefrom all axonal transmission
how do opiates work
reduces sensitivity to nociceptors and block transmitter release in the dorsal horn
activate descending inhibitory pathways
gate control theory
nociceptor fibres come into the dorsal horn and immediately synapse onto 2nd order neurons. decussate and project up thalamus in the lateral spinothalamic tract