Somatosensory Neurones And Receptors Notes

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Lecture 10 Somatosensory neurones and receptors

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General o Somatosensroy NS includes all sensory (or afferent) neural info excluding special senses e.g. from skin, muscle and viscera (organs) o System receives info
? From outside world (sensors beneath skin)= EXTEROreceptors
? About posture/movement (sensors in muscles/tendons)=PROPRIOreceptors
? About internal environment/organs (sensors in viscera/tissues)=
INTEROreceptors o Afferent: proceeding towards a centre (in this case periphery to CNS) o Special senses: Vision, olfaction, hearing, vestibial senses Sensory Modalities o Heat, Cold, Stretch, Acid, Sting, Itch, Press, Stroke, Tickle, Ache o Thermal; Mechanical; Chemical o Labelled line concept - separate pathways for the transmission of information relating to different modalities. Generally accepted for skin/muscle afferents. Primary afferent neurons o Pseudo-unipolar
? Detect sensory stimuli & send message towards the CNS- therefore a type of peripheral neurone (their cell body lies outside the CNS)

With cell bodies in the
? DORSAL ROOT GANGLIA

* Between each vertebra

* Peripheral fibres running with segmental nerves (muscle and skin afferents) or with autonomic nerves (visceral afferent fibres)
? CRNIAL NERVE ROOT GANGLIA

* Cranial nerve outflow (e.g. swelling on Vth nerve= trigeminal ganglion from head region, or on vagus Xth cranial nerve from visceral afferents)

* Fibres running with autonomic nerves Are there specific pathways related to specific sensory modalities?
o Separate pathways for transmission of information relating to different modalities (sensations) from sensory receptor cortex o Concept accepted for most types of somatic (skin & muscle) afferents, but discussion continues about visceral afferents o

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