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Cns 10


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Cns 10

  1. 1. Voluntary Movement <ul><li>Most complex </li></ul><ul><li>Cerebral cortex integration </li></ul><ul><li>Initiated at without external stimuli </li></ul><ul><li>Can become involuntary </li></ul><ul><ul><li>Riding a bicycle </li></ul></ul>
  2. 2. Rhythmic Movement <ul><li>Combination of reflex and voluntary </li></ul><ul><li>Initiated and terminated by input from cerebral cortex </li></ul><ul><li>After initiation becomes reflexive </li></ul><ul><ul><li>Maintained by spinal interneurons </li></ul></ul><ul><ul><li>Example: Running </li></ul></ul>
  3. 3. CNS Integration <ul><li>3 levels of control </li></ul><ul><ul><li>Spinal cord </li></ul></ul><ul><ul><li>Brain stem and cerebellum </li></ul></ul><ul><ul><li>Cerebral cortex and basal nuclei </li></ul></ul><ul><ul><ul><li>Thalamus relay station </li></ul></ul></ul><ul><li>Simple movements </li></ul><ul><ul><li>Spinal reflexes </li></ul></ul><ul><ul><li>Postural reflexes </li></ul></ul><ul><ul><li>Both can have cerebellar input </li></ul></ul>
  4. 4. Integration of Voluntary Movement <ul><li>Coordination between: </li></ul><ul><ul><li>Cerebral cortex </li></ul></ul><ul><ul><li>Cerebellum </li></ul></ul><ul><ul><li>Basal ganglia </li></ul></ul><ul><li>3 steps: </li></ul><ul><ul><li>Decision making and planning </li></ul></ul><ul><ul><li>Initiating movement </li></ul></ul><ul><ul><li>Executing movement </li></ul></ul><ul><li>Feedforward postural reflexes </li></ul><ul><ul><li>Adjustment in anticipation of changes </li></ul></ul>
  5. 5. Voluntary Movement: “Conscious”
  6. 7. <ul><li>Anticipates body movement </li></ul><ul><ul><li>Reflexive adjustment to balance change </li></ul></ul><ul><ul><li>Prepares body for threat: blink, duck, &quot;tuck & roll&quot; </li></ul></ul><ul><li>Combines with feedback </li></ul>Feed Forward: Postural Reflex Feedforward reflexes and feedback of information during movement
  7. 8. Overview <ul><li>Anatomy </li></ul><ul><li>Loops & Pathways </li></ul><ul><li>Motor Disorders </li></ul>1 1 1 1
  8. 9. Basal Nuclei <ul><li>In the cerebral white matter of each hemisphere are a groups of subcortical nuclei called the basal nuclei </li></ul><ul><li>The main mass of this tissue include the caudate nucleus, putamen, globus pallidus (paleostriatum), subthalamic nucleus and substantia nigra </li></ul>
  9. 10. Basal Nuclei <ul><li>The putamen and globus pallidus together form a mass called the lentiform nucleus. </li></ul><ul><li>The comma shaped caudate nucleus arches superiorly over the diencephalon. </li></ul><ul><li>The lentiform nucleus flanks the internal capsule laterally </li></ul><ul><li>Collectively the caudate nucleus and the lentiform nuclei are called the corpus striatum because the fibers of the internal capsule that course past these nuclei give them a striped appearance </li></ul>
  10. 11. Basal Nuclei <ul><li>The basal nuclei are functionally associated with the subthalamic nuclei (located in the floor of the diencephalon) and the substantia nigra(pars compacta and para reticulata) of the midbrain </li></ul><ul><li>The amygdaloid nucleus sits on the tail of the caudate nucleus, functionally it belongs to the limbic system </li></ul>
  11. 12. Basal Nuclei <ul><li>Functionally, the basal nuclei can be viewed as complex neural calculators that cooperate with the cerebral cortex in controlling movement </li></ul>
  12. 13. Basal Nuclei <ul><li>The basal nuclei receive inputs from the entire cerebral cortex as well as from other subcortical nuclei </li></ul><ul><li>Via relays through the thalamus, the basal nuclei project to the premotor and prefrontal cortices </li></ul>
  13. 14. Basal Nuclei <ul><li>Via relays the basal nuclei influence muscle movements directed by the primary motor cortex </li></ul><ul><li>The basal nuclei has no direct access to the motor pathways </li></ul><ul><li>The precise role of the basal nuclei is difficult to determine since their function overlaps to some extent with the cerebellum </li></ul><ul><li>The basal nuclei are particularly important in starting, stopping, and monitoring movements executed by the by the cortex </li></ul>
  14. 15. Components of the Basal Ganglia <ul><li>Input Nuclei </li></ul><ul><ul><li>Corpus Striatum (aka Striatum) </li></ul></ul><ul><ul><ul><li>Caudate </li></ul></ul></ul><ul><ul><ul><li>Putamen </li></ul></ul></ul><ul><li>Output Nuclei </li></ul><ul><ul><li>Globus Pallidus Interna </li></ul></ul><ul><ul><li>Substantia Nigra Pars Reticulata* </li></ul></ul><ul><li>Intermediate Nuclei </li></ul><ul><ul><li>Globus Pallidus Externa </li></ul></ul><ul><ul><li>Subthalamic Nucleus* </li></ul></ul><ul><ul><li>Substantia Nigra Pars Compacta* </li></ul></ul>
  15. 16. Basal Ganglia <ul><li>Non-Motor Loops </li></ul><ul><ul><li>Executive/Prefrontal Loop </li></ul></ul><ul><ul><li>Limbic Loop </li></ul></ul><ul><ul><li>Oculomotor Loop </li></ul></ul><ul><li>Motor Loop (Focus of our journey) </li></ul><ul><ul><li>Regulation of upper motor neurons </li></ul></ul><ul><ul><li>Necessary for normal initiation </li></ul></ul>
  16. 17. Pathways of Motor Loop <ul><li>Direct Pathway </li></ul><ul><ul><li>Overall Excitatory </li></ul></ul><ul><li>Indirect Pathway </li></ul><ul><ul><li>Overall Inhibitory </li></ul></ul>
  17. 18. Direct Pathway (aka the Express Route) CORTEX PUTAMEN (GPe) (STN) GP interna VA/VL THALAMUS Glutamate (+) Glutamate (+) GABA (-) GABA (-)
  18. 19. Indirect Pathway (aka, scenic route) CORTEX PUTAMEN GP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) Glutamate (+) GABA (-) GABA (-) Glutamate (+)
  19. 20. What is missing? <ul><ul><li>Effect of DA on pathways </li></ul></ul><ul><ul><ul><li>Direct Pathway: Stimulates </li></ul></ul></ul><ul><ul><ul><li>Indirect Pathway: Inhibits </li></ul></ul></ul><ul><ul><ul><li>Overall Excitatory </li></ul></ul></ul>
  20. 21. DA in Direct Pathway Substantia Nigra pars compacta Dopamine (+)
  21. 22. DA in the Indirect Pathway Dopamine (-) Substantia Nigra pars compacta
  22. 23. Direct and Indirect Motor Loops CORTEX PUTAMEN (GPe) (STN) GP interna VA/VL THALAMUS Glutamate (+) Glu(+) GABA (-) GABA (-) (--) CORTEX PUTAMEN GP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) GABA (-) GABA (-) Glutamate (+) DA (+) Glu(+)
  23. 24. Striatal Connexions Cerebral cortex Caudate nucleus Putamen Globus pallidus Substantia nigra Tone inhibitor dopamine Thalamus (corticostriate) – motor region (thalamostriate) (Nigrostriate) Striatonigral Inhib GABA striatopallida Subthalamic nucleus Subthalamic fasciculus - - + Pallidonigral 1 2 2 2 3
  24. 26. Command for movement - + + Motor Cortex Basal Ganglia Cerebellum Thalamus
  25. 27. Movement <ul><li>Cortical control – </li></ul><ul><li>“ What is to be done” </li></ul><ul><li>Basal ganglia and cerebellum – </li></ul><ul><li>“ How it is to be done” </li></ul><ul><li>Disease to the extrapyramidal system gives rise to extrapyramidal disorders ( basal ganglia, substantia nigra and subthalamic nucleus ) </li></ul>
  26. 28. Dopamine <ul><li>A Monoamine neurotransmitter </li></ul><ul><li>Formed by an amino acid (tyrosine) which is modified by tyrosine hydroxylase to form DOPA . </li></ul><ul><li>DOPA decarboxylase removes CO2 from DOPA and forms Dopamine which is a precurser to norepinephrine and epinephrine . </li></ul>
  27. 29. Dopamine Systems <ul><li>4 main systems </li></ul><ul><ul><ul><li>Mesolimbic </li></ul></ul></ul><ul><ul><ul><li>Tubero-infundibular </li></ul></ul></ul><ul><ul><ul><li>Incertohypothalamic </li></ul></ul></ul><ul><ul><ul><li>Nigrostriate </li></ul></ul></ul>
  28. 30. Dopamine systems <ul><li>Mesolimbic : cell origin are in the ventral tegmentum of the midbrain which sends axons to the limbic system. Excessive dopamine result in psychotic episodes ex. Schizophrenia. </li></ul><ul><li>Tubero – infundibular : Dopamine release in this system inhibits release of pituitary prolactin and influences oxytocin and vasopressin secretion </li></ul><ul><li>Incertohypothalamic: Dopamine release in this system influences endocrine secretion </li></ul>
  29. 31. Dopamine systems <ul><li>Nigrostriate : Dopamine neurons in the substantia nigra send axons to the caudate nucleus and the putamen as tone inhibitors. </li></ul>
  30. 32. How do I keep this all straight? <ul><li>Basal Ganglia (Caudate, Putamen, and GP) </li></ul><ul><ul><li>Medium Spiny neurons = GABAergic </li></ul></ul><ul><ul><ul><li>GABA = Inhibitory </li></ul></ul></ul><ul><li>Cortex, Thalamus, STN </li></ul><ul><ul><li>Here, looking at Glutamatergic neurons </li></ul></ul><ul><ul><li>Glut=excitatory </li></ul></ul><ul><li>Dopamine from Substantia Nigra pc </li></ul><ul><ul><li>Acts on Putamen </li></ul></ul>
  31. 33. Functions <ul><li>1. Involved in planning and programming of movements. </li></ul><ul><li>2.The nuclei are involved in monitoring muscle movements that are relatively slow and sustained or patterned. </li></ul><ul><li>3. Inhibits the muscle tone </li></ul><ul><li>4. Regulates the subconscious gross movements. </li></ul><ul><li>5. Caudate nucleus – role in cognitive process </li></ul>
  32. 34. Movement Disorders <ul><li>Hyperkinetic </li></ul><ul><ul><li>Hemiballismus </li></ul></ul><ul><ul><li>Huntington’s Disease </li></ul></ul><ul><li>Hypokinetic </li></ul><ul><ul><li>Parkinson’s Disease </li></ul></ul><ul><ul><li>Drug Induced (Neuroleptics) </li></ul></ul>
  33. 35. Hemiballismus CORTEX PUTAMEN GP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) GABA (-) GABA (-) Glutamate (+) Glutamate (+) +
  34. 36. Hemiballismus <ul><li>Injury usually to STN </li></ul><ul><li>Decreased inhibition (Indirect Pathway) </li></ul><ul><li>Characterized by uncontrolled flinging </li></ul><ul><li>TX: Dopamine Antagonist </li></ul>
  35. 37. Huntington’s Disease
  36. 38. Huntington’s Disease CORTEX PUTAMEN GP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) Glutamate (+) GABA (-) GABA (-) Glutamate (+) +
  37. 39. Parkinson’s Disease <ul><li>Loss of DA neurons in substantia nigra </li></ul><ul><li>Four cardinal symptoms </li></ul><ul><ul><li>Bradykinesia, Akinesia, Rigidity, Tremor </li></ul></ul>
  38. 40. Parkinson’s Disease CORTEX PUTAMEN (GPe) (STN) GP interna VA/VL THALAMUS Glutamate (+) Glu(+) GABA (-) GABA (-) (--) CORTEX PUTAMEN GP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) GABA (-) GABA (-) Glutamate (+) DA (+) Glu(+)
  39. 41. Dopamine Clinical symptoms: Occur when 70 %– 80% of Dopamine depleted Decreased Dopamine formation Reduced dopaminergic Impulses to the striatum Enhanced excitation of globus palledus and subthalamic nucleus Increased inhibition of the thalamus Decreased cortical regulation
  40. 43. In Terms of Etiology and Clinical Picture, Major Symptoms Involve: <ul><li>Bradykinesia - Slowness in Initiation and Execution of Voluntary Movements </li></ul><ul><li>Rigidity –it can be lead pipe or cog wheel. Increase Muscle Tone and Increase Resistance to Movement (Arms and Legs Stiff) </li></ul><ul><li>Tremor - Usually Tremor at Rest, When Person Sits, Arm Shakes, Tremor Stops When Person Attempts to Grab Something </li></ul><ul><li>Postural Instability - abnormal fixation of posture (stoop when standing), equilibrium, and righting reflex </li></ul><ul><li>Gait Disturbance - Shuffling Feet </li></ul>
  41. 44. Usually Other Accompanied Autonomic Deficits Seen Later in Disease Process: <ul><li>Orthostatic Hypotension </li></ul><ul><li>Dementia </li></ul><ul><li>Dystonia </li></ul><ul><li>Ophthalmoplegia </li></ul><ul><li>Affective Disorders </li></ul>
  42. 45. Chorea and athetosis <ul><li>Chorea: caudate nucleus damage </li></ul><ul><li>Rapid , irregular involuntary movements of short duration. </li></ul><ul><li>Athetosis: Lenticular nucleus </li></ul><ul><li>Continuous , slow twisting movement. </li></ul>
  43. 46. Pyr system (CS tract) 1. Weakness 2. Spasticity 3. Inc tone 4. No atrophy 5. Babinski UMN lesion 1. Weakness 2. Dec DTR 3. Dec tone 4. Atrophy 5. Downgoing toes LMN lesion EPS (Basal Ganglia) <ul><li>Chorea (Huntington’s, Syndenham’s) </li></ul><ul><li>Athetosis (choreoathetosis in HD) </li></ul><ul><li>Hemiballismus (stroke) </li></ul><ul><li>Parkinson’s disease (resting tremor, bradykinesia, truncal instability, dementia) </li></ul>Cerebellum <ul><li>Intention tremor </li></ul><ul><li>Ataxia (fall towards lesion, gait & trunk dystaxia, dysrhythmokinesia, dysdiadochokinesia, dysmetria) </li></ul><ul><li>Nystagmus </li></ul><ul><li>Dec DTR/tone ipsilaterally </li></ul><ul><li>Asthenia (muscle tire easily ) </li></ul>