Somatosensory System Tactile Limb position proprioception Pain Temperature

Somatosensory System -Tactile -Limb position (proprioception) -Pain -Temperature Body Spinal Cord Thalamus Cerebral Cortex

Mechanoreceptors Pac C: RA; Vibration; A , Aß Ruff C: SA; Stretch; A , Aß Meis C: RA; Flutter; A , Aß Merk D: SA; Pressure; A , Aß Hair R: SRA; Flutter; A , Aß Nociceptors & Thermoreceptors Free NE: Pain & Temp; A∂, C Free NE Merk D Meis C Pac C

Dorsal root ganglion neuron CNS receptors A , Aß = thick, myelinated axon fibers A∂ = thin, lightly myelinated axon fibers C = thin, unmyelinated axon fibers

Spinal Cord Segment Dorsal Horn Dor R DRG Ventral Horn Vent R

Lissaur’s Tract MZ SG Mot N ALS Spinal Segment (Sacral Cord) Dor C VC

Dorsal Column-Medial Lemniscal Pathway: Touch and Proprioception Medial Lem Dorsal Col Nuc Dorsal Column

Anterolateral System: Pain and Temperature Spinal Thalamic -VPL -intralaminar nuclei Spinal Mesencephalic (Spinal tectal) -tectum -periaquiductal grey Spinal Reticular -pons -medulla ALS

Cervical (Upper) Cervical (Enlrg) Thoracic Lumbar

Syryngomyelia

X 5 Cervical Lumbar Thoracic Sacral

X 15 Medial Lemniscus: “Headless Man Standing”

X 20

X 20 PICA Vertebral

X 25

X 35

X 40

X 45

Pain Suppression Periaquiductal grey glutamate Raphe nucleus serotonin Dorsal horn

Pain Suppression Periaquiductal grey enkephalin containing neurons and receptors glutamate Raphe nucleus serotonin Dorsal horn enkephalin containing interneurons inhibit ascending pain information

Pain Suppression Periaquiductal grey enkephalin containing neurons and receptors glutamate Raphe nucleus morphine serotonin Dorsal horn enkephalin containing interneurons inhibit ascending pain information

X 100

X 55

X 120

Area 1 Area 2 Area 3 B Area 3 A

S-II Thal