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Ascending tracts

Ascending tracts 2 -
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Discriminative touch, vibratory sense & conscious muscle joint sense : Posterior white column (Fasciculus gracilis & fasciculus cuneatus) 1st order neuron The axons enter the spinal cord from the posterior root ganglion & pass directly to the posterior white column of the same side The ascending fibers travel upward in the white column as the fasciculus gracilis & cuneatus Fasciculus gracilis is present throughout the spinal cord (Contain ascending fibers from the sacral, lumbar & lower 6 thoracic spinal nerves) Fasciculus cuneatus is situated lateral to the FG in the upper thoracic & cervical segments (Contain ascending fibers from upper 6 thoracic & cervical spinal nerves) FG & FC ascends ipsilaterally & synapses with the 2nd order neurons at medulla oblongata 2nd order neuron The axons are called internal arcuate fibers They decussate with the corresponding fibers from the opposite side in the sensory decussation The fibers then ascend as a compact bundle called the medial lemniscus through medulla, pons & midbrain The fibers synapse with the 3rd order neuron in the ventral posterolateral nucleus of the thalamus Some fibers from the FC enter the cerebellum through the inferior cerebellar peduncle of the same side (Cuneocerebellar tract) 3rd order neuron Axons pass through the posterior limb of the internal capsule & corona radiata to reach the somesthetic area in the post central gyrus of the cerebral cortex Fine touch, localization, 2 point discrimination & vibratory sense can be recognized consciously The main sensory pathways to consciousness The main sensory pathways to consciousness Unconscious muscle joint sense pathways to the cerebellum Unconscious muscle joint sense pathways to the cerebellum Unconscious muscle joint sense pathways to the cerebellum
Ascending tracts Ascending tracts Reviewed by Ucfm on March 02, 2012 Rating: 5
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