1 1) Somatosensory System 2) Mechanoreceptors / Receptor Potentials 3) Muscle Spindles / GTOs 4) Central Somatosensory Processing 5) Deafferentation / Plasticity Topic 5 – Somatosensory System Source: Kandel et al., Principles of Neural Science, McGraw Hill, 20000 Peripheral receptor Dorsal root ganglion cell Peripheral axon proximal axon Spinal cord "First-order" sensory afferents carry info from peripheral receptors to the spinal cord. Source: Purves et al. Neuroscience, Sinauer Associates Inc: Massachusetts, 2001. Vertebra Dorsal Root Ganglion White matter Gray matter Spinal nerve
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Topic 5 – Somatosensory System - York UniversityTopic 5 – Somatosensory System Plasticity - Sensory and motor maps are modifiable by training or use. 10 Somatosensory maps are
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1) Somatosensory System
2) Mechanoreceptors / Receptor Potentials
3) Muscle Spindles / GTOs
4) Central Somatosensory Processing
5) Deafferentation / Plasticity
Topic 5 – Somatosensory System
Source: Kandel et al., Principles of Neural Science, McGraw Hill, 20000
Peripheral receptor
Dorsal root ganglion cell
Peripheral axonproximal axon
Spinal cord
"First-order" sensory afferents carry info from peripheral receptors to the spinal cord.
Source: Purves et al. Neuroscience, SinauerAssociates Inc: Massachusetts, 2001.
Vertebra
Dorsal Root Ganglion
White matter
Gray matter
Spinal nerve
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cerebrum
Primary somatic sensory cortex
Ventral posterior lateral nucleus of thalamus
midbrain
mid-pons
Rostral medulla
Caudal medulla
Cervical spinal cord
Lumbar spinal cord
Medial lemniscus
Medial lemniscus
Gracile nucleus (pathways from lower body)
Cuneate nucleus (pathways from upper body)
Internal arcuate fibers
Gracile tract
Cuneate tract
Mechanosensoryreceptors from upper body
Mechanosensoryreceptors from lower body
Afferent pathway for mechanosensoryinformation:
The dorsal column - medial lemniscus (DCML) pathway
Source: Purves et al. Neuroscience, Sinauer Associates Inc: Massachusetts, 2001.
- carries cutaneous and proprioceptive information to the brain
Dorsal root ganglion
cerebrum
Primary somatic sensory cortex
Ventral posterior lateral nucleus of thalamus
midbrain
mid-pons
Rostral medulla
Caudal medulla
Cervical spinal cord
Lumbar spinal cord
Medial lemniscus
Medial lemniscus
Gracile nucleus (pathways from lower body)
Cuneate nucleus (pathways from upper body)
Internal arcuate fibers
Gracile tract
Cuneate tract
Mechanosensoryreceptors from upper body
Mechanosensoryreceptors from lower body
Source: Purves et al. Neuroscience, Sinauer Associates Inc: Massachusetts, 2001.
Dorsal root ganglion
- afferents travel through dorsal column up to the medulla
cerebrum
Primary somatic sensory cortex
Ventral posterior lateral nucleus of thalamus
midbrain
mid-pons
Rostral medulla
Caudal medulla
Cervical spinal cord
Lumbar spinal cord
Medial lemniscus
Medial lemniscus
Gracile nucleus (pathways from lower body)
Cuneate nucleus (pathways from upper body)
Internal arcuate fibers
Gracile tract
Cuneate tract
Mechanosensoryreceptors from upper body
Mechanosensoryreceptors from lower body
Source: Purves et al. Neuroscience, Sinauer Associates Inc: Massachusetts, 2001.
Dorsal root ganglion
1st order afferents synapse with 2nd order neurons in dorsal column nuclei (gracile and cuneate)
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cerebrum
Primary somatic sensory cortex
Ventral posterior lateral nucleus of thalamus
midbrain
mid-pons
Rostral medulla
Caudal medulla
Cervical spinal cord
Lumbar spinal cord
Medial lemniscus
Medial lemniscus
Gracile nucleus (pathways from lower body)
Cuneate nucleus (pathways from upper body)
Internal arcuate fibers
Gracile tract
Cuneate tract
Mechanosensoryreceptors from upper body
Mechanosensoryreceptors from lower body
Source: Purves et al. Neuroscience, Sinauer Associates Inc: Massachusetts, 2001.
Dorsal root ganglion
2nd order neurons travel through internal arcuate and medial lemniscus tracts to the thalamus
cerebrum
Primary somatic sensory cortex
Ventral posterior lateral nucleus of thalamus
midbrain
mid-pons
Rostral medulla
Caudal medulla
Cervical spinal cord
Lumbar spinal cord
Medial lemniscus
Medial lemniscus
Gracile nucleus (pathways from lower body)
Cuneate nucleus (pathways from upper body)
Internal arcuate fibers
Gracile tract
Cuneate tract
Mechanosensoryreceptors from upper body
Mechanosensoryreceptors from lower body
Source: Purves et al. Neuroscience, Sinauer Associates Inc: Massachusetts, 2001.
Dorsal root ganglion
- 2nd order neurons synapse on 3rd order in VPL nucleus of thalamus
- 3rd order neurons travel to S1
Primary somatosensory cortex (S1)
Source: Kandel et al., Principles of Neural Science, McGraw Hill, 2000