Sensory Receptors: Transduction and Coding Narrado por: Renato M.E. Sabbatini, PhD

adequate stimulus sensory receptor primary afferent neurone synapse 2nd order neurone graded receptor potential threshold generated action potentials frequency coded action potentials conducted down primary afferent neurone synaptic integration action potentials cause transmitter release & generate graded potentials (EPSPs) in 2nd order neurone reduced frequency of action potentials conducted down 2nd order neurone Transduction & Coding related to stimulus intensity and duration transduction and generation of graded receptor potential EPSPs

Sensory Coding for Intensity & Duration amplitude 40mv duration 4ms amplitude 65mv duration 7ms - note decay of receptor potential small amount transmitter released large amount transmitter released exceeds threshold & generates action potentials conducted down sensory axon generates higher frequency of action potentials for longer period more action potentials conducted down sensory axon recording arrangement from sensory unit

Tonic and Phasic Receptors Amplitude Sensitive - Slowly adapting R  p R= response, p = position, t = time Stimulus p t Velocity Sensitive - Rapidly adapting R  dp/dt R  d 2 p/dt 2 Acceleration Sensitive - Rapidly adapting