Motor Functions

Motor Functions

Functions to move the body
Parts of the motor system
1. Motor cortex
  1. Neocortex
    1. Posterior cortex
      1. Specify movement goals and send info to the prefrontal cortex
    2. Prefrontal cortex
      1. Generates plans for movement
    3. Premotor cortex
      1. Recognizes movement of others and selects similar or different actions
    4. Primary motor cortex
      1. Executes movements
  2. Wilder Penfield
    1. Produced movement in different areas of the body by stimulating the precentral gyus
      1. 10+ homunculi in the motor and premotor cortices
2. Basal ganglia
  1. Input from the cortex
    1. Motor cortex
    2. Limbic cortex
    3. Nigrostriatal dopamine pathway
    4. Output to the motor cortex and substantia nigra
  2. Disorders
    1. Involuntary movements = hyperkinetic symptoms
      1. Huntington's chorea
      2. Tourette's syndrome
        Related to damage to the caudate putamen
        Results in tics and vocalizations
    2. Difficulty making movements = hypokinetic symptoms
      1. Parkinson's disease
        Loss of dopamine cells in the substantia nigra and their input to the basal ganglia
        Results in muscular rigidity and difficulty initiating and performing movements
  3. Movement force
    1. Projects to the internal part of the Globus pallidus (GPi)
      1. Excitatory
      2. Inhibitory
      3. GPi
        Projects to the thalamus and the thalamus projects to the cortex
        Influences the thalamic projection
        If inhibited the thalamus will excite the cortex
        Parkinson's disease
        Excessive activity of GPi
        Decreased movement
        Destruction or stimulation of GPi is a treatment
3. Cerebellum
  1. Participates in acquiring and maintaining motor skills
  2. Divided into two hemispheres
  3. The flocculus, a small lobe, projects from the ventral surface
    1. Takes part in balance
  4. Contains about 1/2 of all the neurons in the entire nervous system
  5. Motor learning
    1. Damage to the cerebellum
      1. A loss of timing in movement and perceptrion
      2. Problems with movement accuracy
    2. Feedback circuit between the cortex and cerebellum for movement adjustment
4. Spinal cord
5. Motor neurons
6. Brainstem
  1. Eating and drinking
  2. Sexual behaviour
  3. Ability to stand upright
  4. Coordinated limb movements for swimming and walking
Mirror neurons
1. Neurons that fire when we see others make a movement
2. Encode a complete action
3. Actions can be use to imitate and understand other's actions
4. Fill in the blanks when part of a movement is missing
Communicating with the spinal cord
1. Corticobulbar tract
  1. Major projection from the cortex to the brainstem
  2. Controls facial muscles, and takes part in controlling facial movements
2. Corticospinal tract/pyramidal tract
  1. Major projection from the cortex to the spinal cord
  2. Controls movement of the limbs and body
  3. 95% of the fibers descending from each hemisphere decussate in the brainstem, producing two corticospinal tracts

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