ACB 334 Lecture 11: Somatic Motor

• School: U of S
• Department: Anatomy and Cell Biology
• Course: ACB 334
• Professor: Jen Chlan

Document Summary

*damage to umn or lmn produces different clinical syndromes. Muscle weakness tells us that it is a motor tract lesion. Umn = release inhibition increased reflex and tone. Lmn = less stimulus decreased reflex and tone. Upper motor neurons can originate from either the sc or brainstem (obj. Come directly from the motor cortex (direct pathways): e. g. lateral and anterior cst. Come from brainstem centers (indirect pathways) whose activity is controlled/regulated by other cortical and subcortical regions: list the major pathways and functions associated with the lateral and medial motor systems. Lmn are arranged in sc into medial and lateral groups: lateral group controls distal musculature (fine dexterous) e. g. lateral cst, medial group controls axial musculature (posture) e. g. anterior cst. Movement of corticospinal cortex, and other duccsation (predominantly contralateral tract (direct) frontal and at cervical and limbs parietal areas lumbosacral enlargements) Movement of tract (indirect) magnocellular tegmental division decussation, in the midbrain contralateral limbs (function is uncertain in humans)