University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

292

Pages:

2
Author:

Mariam A.

Motor control Lesions to CNS  Spinal cord just below the medulla. o Loss of any motor drive  immediate flaccid paralysis. o Patient will then experience spinal shock. o There is then hyperreflexia because of plastic changes (reorgonisation).  Decerebration through pons. o Patient experiences decerebrate rigidity (hyperextension of limbs), instead of paralysis. o This is because there are regions in the brainstem that controls motor function. Central pattern generators (CPGs)  Located primarily within the brainstem and spinal cord.  Hypothalamus contains CPGs for eating and drinking. o Electrical stimulation of PVN of hypothalamus causes an alerting reaction, in which the animal looks for water, walks towards it and starts to drink. Descending tracts  Cortico- and rubrospinal tracts. o Transmission of commands for skilled movements. o Connections of motor patterns generated by the spinal cord. o Together, the pathways form the lateral system and descend in the lateral funiculus of the cord.  Reticulospinal tract. o Activation of spinal motor programs for stepping and other stereotypic movements. o Control of upright body posture.  Vestibulospinal tract. o Vestibulular nuclear complex receives input from the vestibular apparatus and proprioceptive inputs from postural muscles. o Generation of tonic activity in antigravity muscles. o Together with the reticulospinal tract, forms the medial system and descend in the medial funiculus of the cord. Generation of force  The below areas scaled positively with an increase of force.  Primary motor and somatosensory cortices. o Controlateral and ipsilateral motor/somatosensory  Basal ganglia. o GPi. o STN.  Thalamus. o Vetrroanterior nucleus. o Ventrolateral nucleus. o Lateral and medial ventroposterior nuclei. Cerebellar control of posture  Posture balance is impaired in individuals with pathology of the anterior superior vermis of the cerebellum.  The vermus is damaged in chronic alcoholism, providing a model for studying the relationship between cerebellar pathology and postural sway.  Improvement to normal levels in balance and reduction in sway and tremor, with changes to vision, touch and stance, provide evidence that adaptive mechanisms recruiting sensorimotor integration can be invoked to compensate for underlying cerebellar vermian-related dysfunction. Conclusions  The motor system is arranged in a hierarchical fashion.  There are multiple levels of control: o Cognitively generated high-level motor commands. o Engagement of automatic central pattern generators. o Spinal reflexes.  Many motor functions are delegated to lower-order control: o Posture is maintained via the vestibulospinal and reticulospinal pathways in the brainstem, not through ongoing activity within the motor cortex. o Learned motor functions (e.g. riding a bike) are delegated to basal ganglia and cerebellum.  Muscle spindles and Golgi tendons organs exert their effects at the segmental (spinal) level, but also provide sensory feedback to higher levels.