Resources for Communication Problems

Tuesday, March 4, 2008



Summary NC259S11

Motor function is hierarchically organized at four arbitrarily identified neuraxial levels, with the spinal cord being the lowest. Motor nuclei of the spinal reflex and cortical projections to muscle fibers. Consequently, the spinal cord is crucial in reflex muscle contractions and voluntary movements. The environmentally triggered reflex responses regulated by the spinal cord include the stretch (myotatic) reflex, withdrawal (flexor) reflex, and crossed extensor reflex. Even though these reflexes are independent of voluntary motor control, intact cortical projections to the spinal cord are important in the regulation of these reflexes. Constantly relayed sensory information, which is vital to coordinated motor activity, is integrated at every level of the nervous system. Spinal lesions that interrupt both cortical and spinal reflex projections to limb muscles result in LMN syndrome. The clinical picture of this syndrome is characterized by flaccid paralysis, absent reflexes, and atrophy of muscle fibers.


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