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Long Sensory Pathways (Somatic Sensation)

- Anterolateral System (Pain and Temperature Pathway) - DCML (Vibration and Proprioception) . Long Sensory Pathways (Somatic Sensation). David A. Morton, Ph.D. Thursday January 31 st , 2013. Objectives. Somatic (general) sensation ALS and DCML pathways Identify pathways on sections.

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Long Sensory Pathways (Somatic Sensation)

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  1. - Anterolateral System (Pain and Temperature Pathway)- DCML (Vibration and Proprioception) Long Sensory Pathways (Somatic Sensation) David A. Morton, Ph.D. Thursday January 31st, 2013

  2. Objectives • Somatic (general) sensation • ALS and DCML pathways • Identify pathways on sections

  3. Somatic Sensation Pathway Overview How many neurons are involved in somatic sensation?

  4. Somatic Sensation Pathway Overview What structures are involved in these pathways?

  5. Somatic Sensation Pathway Overview Will decussation occur? If so, where?

  6. Somatic Sensation Pathway Overview Describe the neurons involved:

  7. Somatic Sensation • General sensation.

  8. Somatic Sensation • General sensation. • Crude (non-discriminative) touch. Cannot localize sensation. • Temperature • Pain • Proprioception • Vibration • Fine (discriminative) touch. Can localize sensation. Anterior lateral system (ALS) Dorsal column-Medial Lemniscus (DCML) Receptor distribution is NOT uniform over the body surface; receptor density varies, as does receptive field size. Results in distorted cortical maps representing different parts of the body.

  9. Anterior Lateral System (ALS) • General sensation. • Crude (non-discriminative) touch. Cannot localize sensation. • Temperature • Pain

  10. Anterior Lateral System (ALS) 1° Order neuron • Location of cell body. • Location of synapse. • Collaterals. • Reflex connections.

  11. Anterior Lateral System (ALS) 1° Order neuron • Location of cell body. • Location of synapse. • Collaterals. • Reflex connections.

  12. Anterior Lateral System (ALS) 2° Order neuron • Location of cell body. • Decussation. • Course of axons. • Location of synapse.

  13. Anterior Lateral System (ALS) 2° Order neuron • Location of cell body. • Decussation. • Course of axons. • Location of synapse.

  14. Anterior Lateral System (ALS) 3° Order neuron • Location of cell body. • Course of axons. • Location of synapse. Post-central gyrus Internal capsule VPL Thalamus

  15. Primary Somatosensory Cortex • Brodmann’sareas. • Somatotopic organization. • Homunculus. Contrast cortex area for hand to elbow.

  16. A vascular lesion of which cerebral artery would result in loss of somatic sensation from the hand? From the foot? * * Lateral view Medial view Anterior view

  17. Ascending visceral afferent input travels in the anterolateral system (dashed) and through multisynaptic circuits via the reticular formation of the brain stem (spino-reticulo-thalamic pathway) (solid). • These fibers influence both specific and diverse areas of the cerebral cortex. • Thalamic relays include intralaminar and midline nuclei and cortical areas include orbitofrontal cortex, insula and anterior cingulate gyrus.

  18. Explain the sensory loss with a pathological enlargement of the central canal at the level of C 5,6,7. Why might there be atrophy of the hand muscles?

  19. Define a dermatome and explain why they are useful. Know the dermatomes represented at the level of the back of the head, shoulder, thumb, middle finger, small finger, nipple, umbilicus, inguinal ligament, big toe, small toe and anus.

  20. Somatic SensationPart II: DCML

  21. Dorsal Column-Medial Lemniscus (DCML) 1° Order neuron • Location of cell body. • Location of synapse. Dorsal column Proprioception, vibration, fine touch

  22. Dorsal Column-Medial Lemniscus (DCML) 1° Order neuron • Location of cell body. • Location of synapse. Gracile tract Cuneate tract

  23. Dorsal Column-Medial Lemniscus (DCML) 2° Order neuron • Location of cell body. • Location of synapse.

  24. Dorsal Column-Medial Lemniscus (DCML) Medulla oblongata (caudal) 2° Order neuron • Location of cell body. • Location of synapse. Gracile nucleus Cuneate nucleus ALS Medial lemniscus Sensory dissociation

  25. Dorsal Column-Medial Lemniscus (DCML) • The somatotopic organization of the Medial Lemniscus (ML): • "Feet down" in medulla. • "Feet lateral" in pons. • "Feet up" in midbrain

  26. Dorsal Column-Medial Lemniscus (DCML) 3° Order neuron • Location of cell body. • Course of axons. • Location of synapse.

  27. Dorsal Column-Medial Lemniscus (DCML) Trace.

  28. Locate the ALS and DCML on the following sections:

  29. Spinal Cord DCML ALS

  30. Medulla 4th ventricle X XII IX, X ALS Olivary nucleus Med lem Pyramid

  31. Pons V ALS Med lem CN V What happened in the Pons?

  32. Midbrain AQ ALS III ML Red nucleus Substantia nigra Cerebral peduncle

  33. Diencephalon 3rd ventricle IC RN Midbrain Cerebped Mamillary bodies

  34. The yellow represents area of a lesion. What sensory loss would you expect? L R

  35. The yellow represents area of a lesion. What sensory loss would you expect? L R • Below the lesion: • Loss of pain and temp from left side • Loss of proprioception/vibration from right side

  36. The right side of the pons is lesioned. What sensory loss would you expect?

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