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Somatosensory II
Mechanosensory Pathways
Question | Answer |
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Distinguish between the dorsal column-medial lemniscus (DC-ML) system and the trigeminal mechanosensory system in terms of the regions of the body from which they receive sensory information. | DC-ML: all tactile and proprioceptive info from body except anterior two thirds of face<br>Trigeminal: tactile and proprioception from anterior two thirds of face |
Name the sensory receptors that convey information through the DC-ML and trigeminal pathways. | - Merkel cell: slow adapt mechanoreceptors<br> - Meissner: rapid adapt MR<br> - Pacinian: rapid<br> - Ruffini: rapid<br> - Crude touch-free nerve endings<br> -Muscle spindle:rapid and slow adapting<br> -Golgi tendon organs: slow<br> -Joint Rcpt:slo |
List the types of sensory information mediated by DC-ML and trigeminal pathways. | Fine touch (Merkel cells, Meissner, Pacinian, Ruffian)<br> Crude touch (free nerve endings)<br> Proprioception (muscle spindles, Golgi tendon organs, joint receptors) |
Explain why crude touch does not localize to a specific sensory pathway | Free nerve endings are mechanicallly sensitive but lack precise localization |
Name the thalamic nuclei to which the DC-ML system projects. Name the thalamic nuclei to which the trigeminal mechanosensory system projects. | DC-ML: ventral posterior lateral<br>Trigeminal: ventral posterior medial |
List the locations of the first, second and third order neurons in the DC-ML system and in the trigeminal mechanosensory system. Identify sites of decussation in both pathways. | DC-ML<br>1 order:peripheral axons in spinal nerves, soma in dorsal root ganglia<br>2 order:soma in gracile and cuneate nuclei, axons decussate at spinal cord midline (internal arcuate tract) |