Rexed's Lamina

Processing of the sensory information Levels of neural integration in sensory systems: 1. Receptor level the sensor receptors 2. Circuit level ascending pathways in the CNS

3. Perceptual level neuronal circuits in the cerebral cortex Processing at the Perceptual Level Motor cortex Somatosensory cortex

Thalamus Reticular formation Pons 2 Circuit level processing in( Spinal

)ascending pathways cord Cerebellum Medulla Free nerve ,endings (pain ) cold, warmth

Muscle spindle Receptor level sensory reception( Joint and transmission kinesthetic ) to CNS receptor

1 Figure 13.2 Rexeds Lamina Some important nuclei Substantia gelatinosa

(II) Nucleus proprius (IV) Dorsal nucleus of Clark Intermediolateral cell column Motor neuron pools

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

Spinal Tracts 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

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 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 Corticospinal Tract Precise, coordinated limb movements

Two neuron pathway upper motor neuron in cerebral cortex lower motor neuron in spinal cord Decussation in medulla

Nucleus reticularis paragigantocellularis Pain inhibitory complex [email protected]