What is upper motor neurons (UMN)?
Motor neurons that originate in the motor region of the cerebral cortex or the brain stem that carry motor information down to the final common pathway, that is, any motor neurons that are not directly responsible to for stimulating target muscle.
What is lower motor neurons (LMN)?
Motor neurons connecting the brainstem and spinal cord to muscle fibers, bringing nerve impulses from the UMNs out to the muscles. Terminates on an effector (muscle).
- Classified based on types of muscle fiber they innervate:
a. Alpha motor neurons (extrafusal muscle fibres –contraction)
b. Gamma motor neurons (intrafusal muscle fibres –proprioception)
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