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The Motor System - Coggle Diagram

- - - - Lesions to the basal ganglia cause abnormal movement which is a factor of Parkinson’s Disease.
        
        There are 4 main structures of the basal ganglia: The striatum, the globus pallidus, the subthalamic nucleus, and the substantia nigra.
        
        When the striatum is at rest, the globus pallidus is topically active, inhibiting the subthalamic nucleus of the thalamus and there is no excitation of the upper motor neurons in the cortex
        
        When the striatum is transiently excited, the globus pallidus is transiently inhibited, and the subthalamic nucleus is disinhibited so other inputs can excite it, leading to the excitation of upper motor neurons in the cortex
        
        The direct pathway facilitates flow through the thalamus via the internal segment and facilitates willed movement
        
        The indirect pathway inhibits flow through the thalamus via the external segment and inhibits spontaneous movement
  - - - One way the signal can travel is from the frontal or parietal cortex to the red nucleus, then the inferior olive, then to the deep nuclei of the cerebellar cortex via the inferior cerebellar peduncle.
      - Another way is that the signal can travel from the frontal or parietal cortex to the pontine nuclei, then crossing the midline to the deep nuclei of the cerebellar cortex via the middle cerebellar peduncle.
      - Lastly, the signal can travel from either the spinal cord or vestibular nuclei to the cerebellar cortex via the inferior cerebellar peduncle.
    - - Another signal can also travel from the cerebellar cortex to the fastigial deep nuclei, then travel to either the superior colliculus or directly to the reticular formation via the inferior cerebellar peduncle, then end at the lower motor neurons
      - Another signal can directly travel from the cerebellar cortex to vestibular nuclei via the inferior cerebellar peduncle and from there go to the lower motor neurons
      - One way the signal can travel is from the cerebellar cortex to the dentate or interposed nuclei and then cross the midline to the superior colliculus via the superior cerebellar peduncle, which from there can travel to the reticular formation and then to the lower motor neurons
      - However, the dentate, interposed, and fastigial nuclei also have pathways to upper motor neurons. The dentate nucleus projects the signal to the premotor cortex, while the interposed and fastigial nuclei project to the motor cortex and brainstem.
    - - Vestibulocerebellum: contains the flocculus and nodulus
      - Spinocerebellum: contains the vermis
      - Pontocerebellum, which can be subdivided into the cerebrocerebellum and the neocerebellum.The cerebrocerebellum are the hemispheres.
    - - There are also deep cerebellar nuclei present, which receive inhibitory inputs from Purkinje cells and collateral excitatory projections from mossy fibers and climbing fibers. The globose and emboliform nuclei associate with the spinocerebellum and help with motor execution. The dentate nucleus associates with the pontocerebellum and helps with motor planning. The fastigial nucleus associates with the vestibulocerebellum and mostly projects back to vestibular nuclei.
      - There are also 3 main types of cerebellar cortex afferents:
        
        Mossy fibers: originate from the deep cerebellar nuclei, medulla, and pons; release glutamate to granule and Golgi cells
        
        Climbing fibers: projects axons from inferior olive, sends excitatory signals to Purkinje cells; can send multiple synapses onto one cell; affects muscle proprioceptors
        
        Multilayered fibers: receives input from raphe nuclei, locus coeruleus and hypothalamus; generally inhibitory
    - - The granule layer contains granule cells whose axons form parallel fibers that release glutamate to golgi cells that release GABA to inhibit other cells
      - The molecular layer of the cerebellum contains dendritic trees of the purkinje cells as well as Basket and stellate cells that cause the inhibition of other cells
      - The purkinje layer has only efferent cells of the cerebellar cortex. It releases GABA and inhibits cells. It projects to deep cerebellar nuclei and vestibular nuclei
- - - - The rubrospinal tract’s central input is from the cortex. It crosses in the pons of the brainstem and compensates for the corticospinal tract.
    - - The tectospinal tract originates in the tectum of the superior colliculus and controls head and neck posture and movement.
        
        There are two types of reticulospinal tracts that primarily innervate gamma motor neurons and begin in the reticular formation of the brainstem. The pontine reticulospinal tract originates in the pons and enhances antigravity reflexes and facilitates extensors. It helps us maintain upright position movements. The medullary reticulospinal tract originates in the medulla and is the opposite because it relieves antigravity muscles and inhibits extensors.