Ascending pathways

Ascending Pathways
SENSORY PATHWAYS
(1) Specific Ascending Pathways
?Carry information of single types of stimulus.
?Pass to ? brainstem & thalamus ? different areas of cerebral cortex.
?Cross to the opposite side of the CNS.
?Pathways transmit information from the somatic receptors ? somatosensory cortex.
?Pathways transmit information from special sensory receptors ? special cortical areas.
SENSORY PATHWAYS
(2) Non-specific Ascending Pathways
?Activated by sensory units of several different types ?
?Signal general information.
?Sensory information ? spinal nerves ? dorsal roots of spinal cord ? brain.
The Dorsal Columns-Medial Lemniscal System
?1st order neuron: ascend up to the medulla oblongata
?2nd order neuron: crosses through medial lemnsci to the thalamaus (ventrolateral complex).
?3rd order neuron: somatosensory area I ? to somatic sensory area II.


The Dorsal Columns-Medial Lemniscal System
?Large myelinated nerve fibers (CV = 30-110 m/sec).
?High degree of spatial orientation of the nerve fibers with respect to their origin.
?More accurate intensity gradation (100 times)
?In the thalamus:
i.Tail end of the body represented by lateral portions
ii.Head and face represented in the medial components of the