HSC 350 Lecture Notes - Lecture 10: Reticular Formation, Upper Motor Neuron, Alpha Motor Neuron
Document Summary
Each alpha motor neuron synapse with multiple fibers within the muscle. The motor unit is defined as alpha motor neuron and the muscle fibers it contacts. Consist of lower & upper motor neurons: lower motor neuron: spinal or brainstem primary alpha motor neuron directly innervates muscle. The connection into the lmn occurs through the lateral corticospinal tract (parallel connection from the sacral, lumber, thoracic to the cervical spine). Consist of the: lateral pathway: involved in voluntary movement of distal muscles under direct cortical control. Input orginates from the motor cortex through the corticospinal tract into lateral pathways. Begins from the motor cortex internal capsule midbrain pon medullary pyramids pyramidal decussation. Input originates from the motor cortex through (1) reticular nuclei or (2) superior colliculus & vesticular nuclei into the ventromedial pathway. Vestibulospinal tracts: bilateral projection from the vestibular nuclei (found the medulla) to the medial ventral horn. Responsible for the head position by reflex activation of neck muscles b.
