Motor function of brain and brain stem ms 2017 dentist
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The presence of ataxia suggests damage to any of the following EXCEPT: B. Thalamus Ataxia is a lack of voluntary coordination of muscle movements that is typically associated with cerebellar dysfunction. The thalamus is not directly involved in motor coordination, so damage to the thalamus would not directly cause ataxia. The other options - cerebellum, vestibular nucleus, and vagal nerve - are all involved in motor coordination and their damage could cause ataxia.
![Central Motor Control Systems
Pyramidal system (corticospinal tract) [lateral pathways]
Extrapyramidal system (everything else: basal ganglia,
cerebellum, brain stem) [ventromedial pathways]
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Motor function of brain and brain stem ms 2017 dentist
- 1. MOTOR FUNCTION OF BRAIN AND BRAIN STEM MS 2017 DENTIST
- 2. OBJECTIVES Describe how skilled movements are planned and carried out. Name the posture regulating parts of CNS and discuss the role of each. Discuss the functions of cerebellum List the pathways to and from the cerebellum. Discuss neurological abnormalities produced by diseases of this part. 2
- 3. Motor Control Hierarchy The brain influences the spinal cord to command voluntary movements Central motor system is a hierarchy of control levels: ◦ Top STRATEGY Association areas of neocortex, basal ganglia ◦ Middle TACTICS Motor cortex, cerebellum ◦ Bottom EXECUTION Brain stem, spinal cord 3
- 4. Hierarchy of Motor Control LEVEL FUNCTION STRUCTURES High Strategy Association areas of neocortex, basal ganglia Middle Tactics Motor cortex, cerebellum Low Execution Brain stem, spinal cord 4
- 5. Control of movement Motor output comes from the motor cortex. Higher centers are required for: Initiation of voluntary movement Regulation of the rate, forcefulness, and smoothness of movement Projects through pyramidal tracts to spinal cord, where it synapses with peripheral motor neurones Other pathways run parallel from cortex, basal ganglia and cerebellum via brainstem and spinal cord - these run outside the pyramidal tract and are called the extrapyramidal system 5
- 6. Overview Cerebral (association) cortex - generates the impulse to act, the design and the planning of movement. Basal ganglia and thalamus - provide the gross motor “programs.’ Motor cortex, brain stem and spinal cord interact to maintain posture and movement execution. Cerebellum - maintains equilibrium and smooth coordination of movement. 6
- 7. Organization of Motor Nervous System
- 8. Motor control systems in the cortex 1. Primary motor cortex : – source of pyramidal tract neurones • Discrete purposeful movements 2. Supplementary motor cortex: - Conception and initiation of movement. - lesions cause deficits in voluntary movement or speech - bilateral movements, fixation movements 3.Premotor cortex: - important in motor coordination. - lesions cause impairments in stability of stance, gait and hand coordination Function--patterns of movement From: Biopsychology, JPJ Pinel 8
- 9. Human area 4 = M1 = primary motor cortex Human area 6 = premotor area (PMA) and supplemental motor area (SMA) = premotor cortex 9
- 10. Primary motor cortex From: Biopsychology, JPJ Pinel 10
- 11. Motor control systems outside the cortex Basal ganglia : - a group of subcortical forebrain nuclei (caudate nucleus, putamen (= striatum), globus palludus, subthalamic nucleus) - modulate patterns of motor activity Cerebellum -controls neural ‘programs’ for the executionl of skilled movements 11
- 12. Organisation of the motor system Brainstem Extrapyramidal Motor pathways Cerebellum Basal ganglia Supplementary motor cortex Pyramidal tract Premotor cortex Primary motor cortex Visual cortex Somatosensory cortex Motor nuclei of the thalamus Prefrontal cortex 12
- 13. Descending Motor Control Higher centers are required for: ◦ Initiation of voluntary movement ◦ Regulation of the rate, forcefulness, and smoothness of movement. Descending tracts - control motor function. Ascending tracts - sensory function for planning and feedback. 13
- 14. Lateral pathways – involved in voluntary movement of the distal musculature; under direct cortical control. Ventromedial pathways – involved in the control of posture and locomotion; under brain stem control. Two Major Groups of Descending Pathways 14
- 15. Summary of the major descending spinal tracts and their points of origin corticospinal tract rubrospinal tract reticulospinal tracts tectospinal, vestibulospinal tracts 15
- 16. Central Motor Control Systems Pyramidal system (corticospinal tract) [lateral pathways] Extrapyramidal system (everything else: basal ganglia, cerebellum, brain stem) [ventromedial pathways] 16
- 17. Pyramidal tract - control most of our fine movements From : The Central Nervous System, P. Brodal Reticulospinal tract - projects from the reticular formation - inhibition or facilitation of movement Vestibulospinal tract - influences postural muscles Tectospinal tract - coordinating head and eye movements as part of the optic reflexes Spinal motor pathways 17MAGDI AWAD SASI LIMU PHYSIOLOGY
- 18. The Cerebellum ◦Center of motor coordination. ◦Helps coordinate voluntary movement and balance. ◦Cerebellar disorders cause incoordination or ataxia. 18
- 20. structure Cerebellum is divided into 3 lobes by 2 transverse fissures ◦ Anterior lobe(paleocerebellum) ◦ Large Posterior lobe(neocerebellum) ◦ Flocculo-nodular lobe (archicerebellum is the oldest lobe)
- 21. Anterior cerebellum and part of posterior cerebellum ◦ Receives information from the spinal cord Rest of the posterior cerebellum ◦ Receives information from the cortex Flocculonodular lobe ◦ Involved in controlling the balance through vestibular apparatus
- 22. Cerebellum I. Vermis II. Intermediate zone III. Lateral zone Within are deep cerebellar nuclei: ◦ Fastigial nucleus ◦ Interpositus nucleus ◦ Dentate nucleus 22MAGDI AWAD SASI LIMU PHYSIOLOGY
- 23. Inputs Cortico -pontocerebellar ◦ From motor and premotor cortex (also sensory cortex) ◦ These tracts supplies the contralateral cerebellar cortex Olivo -cerebellar ◦ From inferior olive ◦ Excited by fibres from ◦ Motor cx ◦ Basal ganglia ◦ Reticular formation ◦ Spinal cord vestibulocerebellar ◦ To the flocculonodular lobe Reticulocerebellar ◦ To the vermis Spinocerebellar tracts ◦ Dorsal spinocerebellar tracts ◦ from muscle spindle, prorpioceptive mechanoreceptor (feedback information) ◦ Ventral spinocerebellar tarcts ◦ From anterior horn cell ◦ excited by motor signals arriving through descending tracts (efference copy)
- 24. OutputsNUCLEUSANATOMICAL AREA This is concerned with overall planning of sequence and timing Thalamus -> cortex Dentate nucleuslateral zone Neocerebellar Cortex control muscles of upper and lower limbs distally -> thalamus -> cortex > basal ganglia - > red nucleus reticular formation Nucleus interpositus Intermediate zone controls muscles of axial body, neck, hip medulla, ponsFastigial nucleusVermis Spinocerebellar Cortex
- 25. 25 Cerebellar Cortex Efferenrts to the Deep Cerebellar Nuclei Vestibulocerebellar Cortex : TO the brainstem ( & not via the DCN) to regulate balance , equilibrium & the VOR ). Consequently , the Deep Cerebellar Nuclei provide the only output of the Neocerebellum and Spinocerebellum . MAGDI AWAD SASI LIMU PHYSIOLOGY
- 26. Functional and phylogenetic Role Phylogenetic denomination Anatomical parts Role Vestibulocerebellum (Archicerebellum) Flocculonodular lobe (+ adjacent vermis) Regulates balance and eye movements. Spinocerebellum (Paleocerebellum) Vermis and intermediate parts of the hemispheres ("paravermis") regulates body & limb movements. Cerebrocerebellum (Neocerebellum) Middle portion of the vermis & Lateral parts of the hemispheres involved in planning & initiation of movement.It has purely cognitive functions as well. 26
- 27. 27 Hemisphere Flocculonodular Lobe Posterolateral Fissure Neocerebellum (Lateral parts of hemispheres ) Spinocerebellum ( medial parts of hemispheres+ Vermis ) Physiologic ( Functional ) divisions of the Cerebellum Neocerebellum , Spinocerebellum snd Vestibulocerebellum
- 28. 28 The lateral portions Inputs from motor and association cortices (through pons) Projections to dentate nucleus primary motor and premotor cortex It interacts with motor cortex in: 1. Planning & programming of movements. 2. Planning & execution of skilled movements. 3. It coordinate movements particularly of the distal limb muscles ( e.g., hand ) which are employed in skilful movement . Anterior Lobe Neocerebellum ( Posterior lobe ) Spino- cerebellum Vestibulocerebellum
- 29. 4. Balistic movement – movement that occurs so quickly that it can not be modified by feedback 5.Multi-joint movements 6. Learning of new movements 7. Timing of motor movements (and cognitive functions) 29MAGDI AWAD SASI LIMU PHYSIOLOGY
- 30. 30 Spinocerebellum ( Paleocerebellum) Consist of vermis & medial parts of the cerebellar hemispheres . It receives (1) Proprioceptive inputs -It is concerned with regulation of muscle tone . (2) it also receives a copy of the “ Motor Plan “”from the motor cortex. Therefore , by comparing plan with performance , it acts as a “ comparator “, and sends impulses back to the cortex to correct movement thereby it coordinates & smoothes ongoing body movements Anterior Lobe Spino- cerebellum Vestibulocerebellum The vermis projects to the brainstem areas concerned with control of axial and proximal limb movements . NB : Whereas the Neocerebellum controls particularly distal limb muscles that are neede for skilled movements , the vemis controls movement of axial and proximal limb muscle which are mainly concerned with gross postural adjustments .
- 31. Vermis Kinesthetic and somatosensory inputs from the spinal cord projections to fastigial nucleus Damage interrupts posture and walking 31
- 32. 32 Vestibulocerebellum ( Floculonodular Lobe): Phylogenetically , it is the oldest part (Archicerebellum ) It has connections to the vestibular nuclei ((balance & equilibrium)). And can induce changes in the VOR ( Vestibulocular Reflex ) Anterior Lobe Spino- cerebellum Vestibulocerebellum
- 33. Intermediate Zone Inputs from red nucleus (brain stem & motor cortex) and somatosensory info from the spinal cord Projects to interpositus nucleus red nucleus (loop) Damage produces rigidity and difficulty in moving limbs Action tremor or intention tremor – a tremor causing movement to occur in a staggered manner during motor act. 33
- 34. A. The presence of ataxia suggests damage to any of the following EXCEPT: A. Cerebellar B. Thalamus C. Vestibular nucleus D. Vagal nerve MAGDI AWAD SASI LIMU PHYSIOLOGY 34
- 35. Function of Cerebellar Nucleus The fastigial nucleus assists stance & gait & controls muscles only in the modes of sitting,standing & walking. The nucleus interposed assists segmental reflexes & speeds the initiation of movement triggered by somatosensory cues. The dentate nucleus assists in tasks requiring fine dextirity. 35MAGDI AWAD SASI LIMU PHYSIOLOGY
- 36. 36 Summary of Connections & Functions FunctionOutputsInputsCortexDeep Nuclei Planning and executive of voluntary & skilledhand movements SCP to VA/VL Corticopontin e/ pontocerebell ar Lateral portions of Cerebellar Hemisphere DentateNeo- cerebellum Muscle tone , posture & coordination of movements SCP to Red Nucleus; Fastigial to RF Spinal and brainstem paths Vermis & Medial portions of Cerebellar hemispheres Interpose d; Fastigial Spino- cerebellum Balance , equilibrium & VOR Vestibular nuclei; RF Vestibular nuclei FlocculonodularFastigialVestibulo- cerebellum MAGDI AWAD SASI LIMU PHYSIOLOGY
- 37. 37 Cerebellar Hemispheric Lesions Cerebellar lesions cause no paralysis or sensory deficit . However , upon physical examination , signs such as hypotonia and pendular reflexes can be elicited . Once the patients attempts movement , ataxia appears . What is ataxia ? Ataxia is incoordination of due to errors in the rate , range , force and direction of movement . With circumscribed lesions , the ataxia may be confined/localized to only one part of the body . MAGDI AWAD SASI LIMU PHYSIOLOGY07ذو،الحجة1440
- 38. 38 The Difference Between Lesions of the Cerebellar Cortex & Lesions of DCN If only the cortex of the cerebellum is involved , the movement abnormalities gradually disappear as “ compensation ” occurs . However , lesions of the DCN produce more generalized defects , and abnormalities are permanent . For this reason , care should be taken to avoid damaging the DCN when surgery is undertaken to remove a tumor involving part of the cerebellar cortex . MAGDI AWAD SASI LIMU PHYSIOLOGY
- 39. 39 I/Ataxia (lack of coordination of muscle movement ) , which is manifested by (1) Wide-based , unsteady “ drunken , or staggering “ gait . (2) Scanning speech (3) Dysmetria ( also called Past-Pointing ) (4) “ Intention Tremor ” , oscillation which is characteristic of cerebellar disease . This cerebellar tremor , unlike that of Parkinson’s disease , is absent at rest . A/ Hemispheric Lesions MAGDI AWAD SASI LIMU PHYSIOLOGY07ذو،الحجة1440
- 40. 40 II/ Inability to “ put on the brakes ” i.e., inability to stop movement promptly . Normally , for example , flexion of the forearm against resistance is quickly checked when the resistance force is suddenly broken off . The patient with cerebellar disease can not break the movement of the limb , and the forearm flies back in a wide arc . This abnormal response is known as the “ Rebound Phenomenon ”. III/ Adiadochkinesia ( Dysdiadochkinesia ) : Inability to perform rapidly alternating opposite movements such as repeated pronation and supination of the hands . Hemispheric Lesions ( Contd ) MAGDI AWAD SASI LIMU PHYSIOLOGY07ذو،الحجة1440
- 41. 41 Conclusion Cerebellum hemispheres control the same ( ipsilateral ) side of the body . Purkinje cells are the main output neurons of the cerebellar cortex & project to the deep nuclei of the cerebellum. They are inhibitory to the DCN . The deep cerebellar nuclei ( DCN ) project out to brainstem and thalamic targets via the superior cerebellar peduncles. They are excitatory , but in turn , are themselves inhibited ( switched off ) by Purkinje cells . Flocculonodular lobe is important for regulation of balance , equilibrium & the VOR . MAGDI AWAD SASI LIMU PHYSIOLOGY07ذو،الحجة1440
- 42. Textbook of Medical Physiology -Guyton and Hall, Ch. 55, 56 Neuroscience Bear et al., Ch. 14 42MAGDI AWAD SASI LIMU PHYSIOLOGY07ذو،الحجة1440