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Motor division of nervous system


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Motor division of nervous system

  2. 2.  Lowest level of motor neuron-LMN Primary motor area neuron in cerebral cortex-UMN
  3. 3. MOTOR ACTIVITY OCCURS AT 3LEVELS Spinal cord level -as a reflex action Brain stem level- as a cranial reflex action Cortical level- as a voluntary action
  4. 4.  LMN receive input from UMN Most of the UMN synapse with interneurons Some synapse with LMN UMN originate from cerebral cortex,motor centres of brain stem,red nucleus,vestibular nucleus,sop.colliculus ,reticular formation
  5. 5.  UMN from cerebral cortex reg.vol. motor activity UMN from brain stem reg. muscle tone,posture and equilibrium
  6. 6. Somatic motor pathway Direct motor/pyramidal Indirect motor/extrapyramidal IncludesReticulospinalTectospinalVestibulospinalRubrospinalolivospinal
  7. 7. Motor areas of brain Primary motor area located in precentral gyrus. Brodman’s area.(area 4) Betz cells are the characteristic feature of primary motor area. Topographical representaion (motor homunculus) of entire body.
  8. 8. Contd..• body representation in this area is inverted & unilateral with the head represented down & foot up.• Bilateral representation is seen to LMN, innervating the upper half of face,muscles of eyes,jaws,pharynx,larynx,neck,thorax & abdomen.
  9. 9. Contd… Supplementary motor area-medial part of frontal lobe to upper part of cingulate sulcus where the entire body representation is seen. Area 6- premotor area or motor association area. Major descending tracts which arise from these areas which control motor activity – PYRAMIDAL TRACT
  10. 10. PYRAMIDAL TRACT Information from cerebral cortex for voluntary motor activity. 60 % fibres arise from primary motor cortex (area 4.) 40% fibres from supplementary or secondary motor area and from sensory areas(area 3,1,2) 80% motor area. 20% sensory area.
  11. 11.  Motor nuclei of the cranial nerves in which these axons terminate are that of 3,4,5,6,7,9,10,11,12 cranial nerves – CORTICO NUCLEAR OR CORTICO BULBAR fibres. Rest form CORTICO SPINAL fibres.
  12. 12. Contd… In medulla 80% of fibres cross to opp side(controlateral)as pyramidal deccusation. 20% pass uncrossed(ipsilateral). Crossed fibres occupy lat funiculus of spinal cord & go as lat corticospinal tract. Uncrossed fibres in spinal cord forms ant corticospinal tract.
  13. 13.  Right cerebral cortex controls muscles of left side of the body and left cerebral cortex controls the muscles of right side of the body.
  14. 14. EXTRAPYRAMIDAL TRACTS All descending tracts other than pyramidal tract. Back ground tone, posture ,equilibrium etc. are maintained. Arise from cerebral cortex & from sub cortical structures like basal ganglia , brainstem, reticular formation, red nucleus, tectal nucleus, vestibular nucleus & olivary nucleus.
  15. 15. Cortically originating A) facilitatory fibres.- (+) muscle tone and stretch reflex.(area6,supp.motor area ,& area 7) B) inhibitory fibres- (-) motor activity or reflexes.(suppressor strips of diff areas of cortex like 4s 2s 8s 19s 24s etc.)
  16. 16.  Cortically originating extra pyramidal fibres descend intermingled with pyramidal tract fibres. so any leison of pyramidal tract in brain will be associated with extra pyramidal manifestations.
  17. 17.  Cortically occuring extra pyramidal fibres do not go directly to the alpha motor neuron instead relay in the reticular formation directly or indirectly through the basal ganglia. So reticular formation-relay & integrating centre of extrpyramidal influences.
  18. 18. 2.Reticulospinal Fibres arising from the reticular formation 1) anterior 2) lateralConsists of 2 parts1.bulboreticular facilitatory area maintain nl muscle tone.2.caudal inhibitory area
  19. 19. 3.Vestibulo spinal Arise from lat vestibular nucleus Recieves connection from inner ear, cerebellum, cortex, reticular formation. Facilitate activity of extensor group of muscles-those that maintain posture.
  20. 20. 4.Rubrospinal Arise from red nucleus of mid brain. Connections to cortex, cerebellum, ret formation. 2 parts – magno cellular parvo cellular Forrel’s deccusation. Maintain flexor group of muscles.
  21. 21. 5.Olivospinal Arise from inf. olivary nucleus in medulla. Connected to cortex,cerebellum, thalamus, red nucleus, reticular formation.
  22. 22. 6.Tectospinal Arise from neurons in sup colliculus. Terminate in upper seg of spinal cord. Concerned with spino visual reflex.