2. Processing of the sensory information
Levels of neural integration in sensory systems:
Receptor level — the sensor receptors
Circuit level — ascending pathways in the CNS
Perceptual level — neuronal circuits in the cerebral cortex

3. Processing at the Perceptual Level
Motor
cortex
Somatosensory
cortex
Thalamus
Reticular
formation
Cerebellum
Pons
Medulla 2
Circuit level
(processing in
ascending pathways)
Spinal
cord
Free nerve
endings (pain,
cold, warmth)
Muscle
spindle 1
Receptor level
(sensory reception
and transmission
to CNS)
Joint
kinesthetic
receptor
Figure 13.2

6. Rexed’s Lamina Some important nuclei Substantia gelatinosa (II)
Nucleus proprius (IV)
Dorsal nucleus of Clark
Intermediolateral cell column
Motor neuron pools

8. * * SUMMARY: PATHWAYS IN THE SPINAL CORD
Ascending (afferent) pathways (sensation)
Descending (efferent) pathways (motor commands) * *

9. Spinal Tracts

10. Dorsal Column Ascending Pathway
Deep touch, visceral pain, vibration, and proprioception
Fasciculus gracilis and cuneatus carry signals from arm and leg
Decussation of 2nd order neuron in medulla
3rd order neuron in thalamus carries signal to cerebral cortex

11. Spinothalamic Pathway
Pain, pressure, temperature, touch,
Decussation of the second order neuron occurs in spinal cord
Third order neurons arise in thalamus and continue to cerebral cortex

12. Spinoreticular Tract Pain signals from tissue injury
Decussate in spinal cord and ascend with spinothalamic fibers
End in reticular formation (medulla and pons)
3rd and 4th order neurons continue to thalamus and cerebral cortex

13. Corticospinal Tract Precise, coordinated limb movements
Two neuron pathway
upper motor neuron in cerebral cortex
lower motor neuron in spinal cord
Decussation in medulla

14. Pain inhibitory complex
Nucleus reticularis paragigantocellularis
Pain inhibitory complex