somatosensory function Flashcards
sensory pathways: explain the ascending pathways transmitting sensory information andsomatotropicorganisationwithin the pathway
pathway of stimuli from face
face mechanoreceptor -> primary sensory neurone -> posterior pons -> secondary sensory neurone -> pass through midbrain -> thalamus -> tertiary sensory neurones -> somatosensory cortex
pathway of [innocuous mechanical] stimuli from upper limb (above T6)
upper limb mechanoreceptor -> [AB] primary sensory neurone -> enter posterior cervical cord via dorsal horn -> up cuneate fasciculus (ipsilateral lateral) -> enter cuneate nucleus of posterior medulla oblongata -> synapse and decussation up medial lemniscus through pons as secondary sensory neurone -> pass through midbrain -> thalamus -> tertiary sensory neurones -> somatosensory cortex
pathway of stimuli from lower limb (below T6)
lower limb mechanoreceptor -> primary sensory neurone -> posterior lumbar cord-> up gracile fasciculus (ipsilateral medial) -> enter gracile nucleus of posterior medulla oblongata -> synapse and decussation up medial lemniscus through pons as secondary sensory neurone -> pass through midbrain -> thalamus -> tertiary sensory neurones -> somatosensory cortex
what are size of somatotropic areas proportional to
density of sensory receptors in that body region (somatosensory homonculus)
where do pain and temperature sensations ascend within and decassate in
ascend within lateral spinothalamic tract (decassate in spinal cord before reaching medulla)
where does crude touch ascend within and decassate in
ascends within anterior spinothalamic tract (decassate in spinal cord before reaching medulla)
where do ligh touch, vibration and 2-point discrimination ascend within and decassate in
dorsal column (decassates in medulla)
testing integrity of ascending pathways using QST: spinothalamic stimuli
temperature and pain
testing integrity of ascending pathways using QST: dosral column stimuli
discriminative touch and 2-point discrimination
