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Chapter 08: Movement


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The control of movement by the body and the brain and a look at diseases of movement.

Published in: Health & Medicine, Education

Chapter 08: Movement

  1. 1. Brain Mechanisms of Movement
  2. 2. Role of the Cerebral Cortex <ul><li>Primary Motor Cortex </li></ul><ul><li>Precentral gyrus of the frontal cortex stimulation elicits movements </li></ul><ul><li>Axons from Primary Motor Cortex go to basal ganglia while other motor axons go to the brainstem & spinal cord </li></ul><ul><li>Cerebral Cortex & Complex Actions </li></ul><ul><li>Stimulation of motor cortex elicits complex movement patterns </li></ul><ul><li>The motor cortex is stimulated when movement is imagined </li></ul>
  3. 3. Areas Near the Primary Motor Cortex Posterior Parietal Cortex Primary Somatosensory Cortex Prefrontal Cortex Premotor Cortex Supplementary Motor Cortex
  4. 4. Connections from the Brain & Spinal Cord <ul><li>Dorsolateral Tract </li></ul><ul><li>Axons from the primary motor cortex & red nucleus synapse in the spinal cord </li></ul><ul><li>Pyramids in medulla contain dorsolateral tract crossing that contralaterally controls movements of the fingers, toes, hands, etc. </li></ul>
  5. 5. Connections from the Brain & Spinal Cord <ul><li>Ventromedial Tract </li></ul><ul><li>Contains axons from the primary motor cortex, supplementary motor cortex, midbrain tectum, reticular formation & the vestibular nucleus </li></ul><ul><li>Axons from the ventromedial tract go to both sides of the spinal cord & are largely responsible for neck, shoulder, & trunk movements </li></ul>
  6. 6. The Role of the Cerebellum <ul><li>Involved in Motor Control & Learned Motor Behavior </li></ul><ul><li>Linked to Habit Formation, Aspects of Attention, Timing, & Other Psychological Motor Functions </li></ul>
  7. 7. The Cerebellum <ul><li>Cellular Organization </li></ul><ul><li>Receives input from the spinal cord, from each sensory system via the cranial nerve nuclei, & cerebral cortex where it eventually reaches the cerebellar cortex </li></ul><ul><li>Neurons in the cerebellar cortex are: </li></ul><ul><li>1. Arranged in precise geometrical patterns with multiple repetitions of the same unit </li></ul><ul><li>2. Action potentials of parallel fibers excite one Purkinje cell after another </li></ul><ul><li>3. Purkinje cells inhibit cells of the nuclei of the cerebellum & the vestibular nuclei in the brain stem </li></ul><ul><li>4. Output of Purkinje cells control the timing of movements including turning on & off </li></ul>
  8. 8. Basal Ganglia <ul><li>Includes: Caudate Nucleus, Putamen, & Globus Pallidus </li></ul><ul><li>Caudate nucleus & Putamen are input, globus pallidus is output </li></ul><ul><li>Important for Habit Learning & the Selection of Movement </li></ul><ul><li>Obsessive-compulsive disorder is linked to increased activity in the caudate nucleus & prefrontal cortex </li></ul>
  9. 9. Parkinson’s Disease <ul><li>Symptoms </li></ul><ul><li>Rigidity, resting tremor, slow movements & difficulty initiating physical & mental activity, cognitive defects in memory & reasoning </li></ul><ul><li>1 in 100 with onset after age 50 </li></ul><ul><li>Immediate cause: gradual progressive death of neurons in Substantia Nigra </li></ul><ul><li>Possible causes: Genetics; MPTP, a chemical that the body converts into MPP (a toxin destroys dopamine neurons; probably a mixture of causes </li></ul>
  10. 10. Parkinson’s Disease <ul><li>Standard Treatment </li></ul><ul><li>L-Dopa </li></ul><ul><li>Precursor to dopamine </li></ul><ul><li>Effectiveness varies </li></ul><ul><li>Doesn’t prevent the loss of dopamine containing neurons & may contribute to the death of neurons </li></ul><ul><li>Produces harmful side-effects </li></ul><ul><li>Alternative Treatments </li></ul><ul><li>Antioxidant drugs </li></ul><ul><li>Direct dopamine agonists </li></ul><ul><li>Glutamate antagonists </li></ul><ul><li>Neurotrophins </li></ul><ul><li>Apoptosis blockers </li></ul><ul><li>High frequency electrical stimulation of the Globus Pallidus </li></ul><ul><li>Surgical damage to the Globus Pallidus or parts of the Thalamus </li></ul>
  11. 11. Huntington’s Disease <ul><li>Severe Degenerative Neurological Disorder </li></ul><ul><li>Symptoms: twitches, tremors, & writing movements; depression, memory deficits, anxiety, hallucinations, delusions, poor judgment, alcoholism, drug abuse, & sexual disorders </li></ul><ul><li>Affects 1 in 1000 </li></ul><ul><li>Gradual, extensive brain damage especially in the Caudate Nucleus, Putamen, & Globus Pallidus </li></ul>
  12. 12. Huntington’s Disease <ul><li>Onset </li></ul><ul><li>Most often appears between 30 & 50 years </li></ul><ul><li>The earlier the onset, the faster the deterioration </li></ul><ul><li>Heredity </li></ul><ul><li>Caused by an autosomal dominant gene on chromosome 4 </li></ul><ul><li>Abnormal form of huntingtin , a protein found in neurons that interferes with several metabolic pathways </li></ul>