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Somatic Motor System Motor Tracts Brainstem Motor Centers System Controls 2 Aspects of Movement Spinal Motor Centers Ventromedial System Somatic Motor.

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Presentation on theme: "Somatic Motor System Motor Tracts Brainstem Motor Centers System Controls 2 Aspects of Movement Spinal Motor Centers Ventromedial System Somatic Motor."— Presentation transcript:

1 Somatic Motor System Motor Tracts Brainstem Motor Centers System Controls 2 Aspects of Movement Spinal Motor Centers Ventromedial System Somatic Motor System Voluntary Movement Patient Case Cortical Motor Centers Map of Essential Concepts DM McKeough © 2009 Postural Set Postural Set and Limb Manipulation Limb Manipulation Lesion Effects Motor Hierarchy Dorsolateral System

2 Motor System  Somatic Motor System Somatic Motor System Somatic Motor System  Voluntary movement Voluntary movement Voluntary movement Motor system controls 2 aspects of movement Motor system controls 2 aspects of movement Motor system controls 2 aspects of movement Motor system controls 2 aspects of movement Dorsolateral motor system Dorsolateral motor system Dorsolateral motor system Dorsolateral motor system Ventromedial motor system Ventromedial motor system Ventromedial motor system Ventromedial motor system Motor tracts Motor tracts Motor tracts Motor tracts Motor centers of the cerebral cortex Motor centers of the cerebral cortex Motor centers of the cerebral cortex Motor centers of the cerebral cortex Motor centers of the brainstem Motor centers of the brainstem Motor centers of the brainstem Motor centers of the brainstem Motor centers of the spinal cord Motor centers of the spinal cord Motor centers of the spinal cord Motor centers of the spinal cord Motor hierarchy Motor hierarchy Motor hierarchy Motor hierarchy Posture and limb manipulation Posture and limb manipulation Posture and limb manipulation Posture and limb manipulation Lesion effects Lesion effects Lesion effects Lesion effects Patient case Patient case Patient case Patient case Last Viewed Last Viewed Exit Concept Map Concept Map

3 Output: 3 classes of movement  Voluntary movement: purposeful, goal directed, complex, learned movements (ADL)  Rhythmic, repetitive motions (walking): initiation and termination of a sequence of relatively stereotyped and almost automatic voluntary movements  Reflex responses: normal, rapid, stereotyped, involuntary movement initiated by a stimulus Somatic Motor System Motor Control System Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

4 Voluntary Movement Originates in the Brain 1/3 Spinal Cord (LMN) Proprioceptors Thalamus S1 Assoc Ctx M1 (UMN) Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

5 Control of Voluntary Movement 2/3 The motor control system consists of Upper motor neurons (UMN) Originate in motor centers in the brain Cross the midline Terminate on lower motor neurons in the brainstem and spinal cord Lower motor neurons (LMN) Originate in motor centers in the brainstem and spinal cord Exit the CNS via cranial and spinal nerves Initiate movement by commanding skeletal muscles to contract UMN LMN Stimulus Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

6 UMN Termination 3/3 Vast majority (~90%) of UMN terminate on interneurons that then connect to LMN (polysynaptic connection) Vast majority (~90%) of UMN terminate on interneurons that then connect to LMN (polysynaptic connection) Allows integration Allows integration Minority of UMN (~10%) make monosynaptic connection with LMN Minority of UMN (~10%) make monosynaptic connection with LMN Pincer grip (most precise prehension) Pincer grip (most precise prehension) UMN Reciprocal Inhibition Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

7 Control of Voluntary Movement Independent limb manipulation Independent limb manipulation Controlled via the dorsolateral motor system Controlled via the dorsolateral motor systemdorsolateral Posture and balance Posture and balance Controlled via the ventromedial motor system Controlled via the ventromedial motor systemventromedial System comparison System comparison System comparison System comparison In general, the MC system may be seen as having 2 independent systems concerned with controlling 2 primary aspects of movement: Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

8 Organization of the System Dorsolateral system: dedicated to the control of skilled (fractionated) movement of contralateral limbs (appendicular skeleton) Dorsolateral system: dedicated to the control of skilled (fractionated) movement of contralateral limbs (appendicular skeleton) Corticobulbar tract Corticobulbar tract Lateral corticospinal tract Lateral corticospinal tract Lateral corticospinal tract Lateral corticospinal tract Rubrospinal tract Rubrospinal tract Rubrospinal tract Rubrospinal tract Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

9 Serial and Parallel Processing 1/3 MC system uses both serial and parallel processing MC system uses both serial and parallel processing Serial processing: 2 neuron system Serial processing: 2 neuron system Upper Motor Neuron (UMN): projects from higher motor control center (cortex or brainstem) to lower motor center (spinal cord) Upper Motor Neuron (UMN): projects from higher motor control center (cortex or brainstem) to lower motor center (spinal cord) Lower Motor Neuron (LMN): projects from the ventral horn to the muscle Lower Motor Neuron (LMN): projects from the ventral horn to the muscle Alpha LMN : large diameter neuron that innervate skeletal (extrafusal) muscle Alpha LMN : large diameter neuron that innervate skeletal (extrafusal) muscle Organized into small, medium, and large motor units Organized into small, medium, and large motor units Beta LMN: intermediate diameter neuron that innervates both extrafusal and intrafusal muscle fibers (  - co- activation) Beta LMN: intermediate diameter neuron that innervates both extrafusal and intrafusal muscle fibers (  - co- activation) Gamma LMN : small diameter neurons that innervate intrafusal muscle fibers (static and dynamic) Gamma LMN : small diameter neurons that innervate intrafusal muscle fibers (static and dynamic) ά Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

10 (+) (-) Dorsolateral Motor System Proprioceptive Reflex Connections 2/3 Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

11 Serial and Parallel Processing 3/3 MC system uses both serial and parallel processing MC system uses both serial and parallel processing Serial processing: 2 neuron system Serial processing: 2 neuron system Parallel processing: normal movement is the result of the simultaneous output of both systems Parallel processing: normal movement is the result of the simultaneous output of both systems Ventromedial system controls involuntary postural and balance reactions. Ventromedial system controls involuntary postural and balance reactions. Postural anticipation of balance disturbance occurs first Postural anticipation of balance disturbance occurs first Dorsolateral system controls voluntary limb manipulation Dorsolateral system controls voluntary limb manipulation Movement of extremities represents a perturbation to balance Movement of extremities represents a perturbation to balance Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

12 Cortical Motor Centers 1/5 Cortical Primary motor cortex (Precentral gyrus, MI, Area 4) Primary motor cortex (Precentral gyrus, MI, Area 4) Premotor cortex (MII, Area 6) Premotor cortex (MII, Area 6) Frontal eye field (Area 8) Frontal eye field (Area 8) Broca’s area (Areas 44 & 45) Broca’s area (Areas 44 & 45) Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

13 Association and Supplementary Motor Areas Desired outcome of the action (Goal) Premotor Area Movement strategy Primary Motor Area Motor plan/ execution Cerebellum Timing, coordination, motor learning Function of the Various Motor Areas 2/5 Goal StrategyPlanExecution How movement occurs Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

14 Somatotopic Organization 3/5 Motor Homunculus Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

15 Comparison of Motor and Sensory Homunculi 4/5 Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

16 Homunculus 5/5 Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

17 Brainstem Motor Centers Tectum Tectospinal Brainstem Brainstem Tectum Tectum Vestibular nuclei Vestibular nuclei Reticular nuclei Reticular nuclei Basal ganglia Basal ganglia Cerebellum Cerebellum Tectum Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

18 Spinal Motor Centers 1/2 Ventral horn is comprised of cell bodies of alpha and gamma lower motor neurons with somatotopic organization Ventral horn is comprised of cell bodies of alpha and gamma lower motor neurons with somatotopic organization Dorsolateral LMN pool: controls voluntary movement of the extremities, particularly the hands (manipulation), receives UMN input form dorsolateral system Dorsolateral LMN pool: controls voluntary movement of the extremities, particularly the hands (manipulation), receives UMN input form dorsolateral system Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

19 Spinal Motor Centers 2/2 Ventromedial LMN pool: controls the trunk (posture and balance), receives UMN input from ventromedial system Ventromedial LMN pool: controls the trunk (posture and balance), receives UMN input from ventromedial system Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

20 Lateral Corticospinal Tract Click to animate Upper motor neuron Pyramidal decussation Lateral corticospinal tract UMN LMN Stimulus Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

21 Click to animate Rubrospinal Tract Upper motor neuron Pyramidal decussation Lateral corticospinal tract UMN LMN Stimulus Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

22 Central Pathways Tectospinal Ventromedial system: dedicated to the control of posture and balance Ventromedial system: dedicated to the control of posture and balance Vestibulospinal tract Vestibulospinal tract Vestibulospinal tract Vestibulospinal tract Reticulospinal tract Reticulospinal tract Reticulospinal tract Reticulospinal tract Tectospinal tract Tectospinal tract Tectospinal tract Tectospinal tract Ventral corticospinal tract Ventral corticospinal tract Ventral corticospinal tract Ventral corticospinal tract Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

23 Lateral Vestibulospinal Tract Click to animate UMN Stimulus Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

24 ReticulospinalTract Click to animate UMN Stimulus Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

25 Click to animate Tectospinal Tract UMN Stimulus Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

26 Click to animate Ventral Corticospinal Tract UMN Stimulus Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

27 Comparison of Dorsolateral and Ventromedial Motor Systems Dorsolateral System Ventromedial System Function Skilled (fractionated) movement of contralateral limbs Posture Balance TractsCrossed Lateral corticospinal RubrospinalCorticobulbar Crossed and uncrossed Vestibulospinal ReticulospinalTectospinal Ventral corticospinal Spinal projection Lateral column Ventral column Spinal termination Dorsolateral lower motor neuron pool Ventromedial lower motor neuron pool Body segments Distal limb segments Trunk Proximal limb segments Muscles (+) flexors (  ) extensors (+) extensors (  ) flexors Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

28 Posture and Manipulation 1/3 Postural set Postural set Auto-regulation: ventromedial system sets proprioceptors (muscle spindle, GTO, joint receptors) to automatically maintain position. Auto-regulation: ventromedial system sets proprioceptors (muscle spindle, GTO, joint receptors) to automatically maintain position. Independent limb manipulation Independent limb manipulation Movement command: dorsolateral system over- rides postural system (resets proprioceptors) to produce independent limb manipulation. Movement command: dorsolateral system over- rides postural system (resets proprioceptors) to produce independent limb manipulation. Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

29 Postural Set Tectospinal tract 2/3 Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

30 LimbManipulation3/3 Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

31 Lesion Effects 1/3 Gray matter lesions Gray matter lesions The body regions and functions served by affected cell bodies The body regions and functions served by affected cell bodies Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

32 Lesion Effects 2/3 White matter lesions White matter lesions Interruption of the information transmitted along that tract Interruption of the information transmitted along that tract All effects are generalized below the lesion level All effects are generalized below the lesion level Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

33 Involuntary Movement 3/3 S&S of Cerebellar lesions: S&S of Cerebellar lesions: Tremor on intention: proximal, slow Tremor on intention: proximal, slow Ataxia: trunk or limb Ataxia: trunk or limb Dysmetria Dysmetria Dysdiadochokinesia Dysdiadochokinesia Hypotonia: proximal > distal Hypotonia: proximal > distal Dysarthria (scanning speech pattern) Dysarthria (scanning speech pattern) Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

34 Motor Hierarchy MC system consists of 3 levels MC system consists of 3 levels Highest level: association cortex, sensory, and motor areas Highest level: association cortex, sensory, and motor areas Concern: select movement goal and strategy Concern: select movement goal and strategy Middle level: BG, Cb, and brainstem motor centers Middle level: BG, Cb, and brainstem motor centers Concern: specifying spatial, temporal, and force parameters of the motor plan Concern: specifying spatial, temporal, and force parameters of the motor plan Lowest level: LMNs, motor plant, FB about sensory consequences of the movement Lowest level: LMNs, motor plant, FB about sensory consequences of the movement Concern: producing the movement pattern and supplying sensory FB Concern: producing the movement pattern and supplying sensory FB S1 Click to Animate Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

35 Motor Tracts Dorsolateral motor system Dorsolateral motor system Lateral corticospinal tract Lateral corticospinal tract Lateral corticospinal tract Lateral corticospinal tract Rubrospinal tract Rubrospinal tract Rubrospinal tract Rubrospinal tract Ventromedial motor system Ventromedial motor system Vestibulospinal tract Vestibulospinal tract Vestibulospinal tract Vestibulospinal tract Reticulospinal tract Reticulospinal tract Reticulospinal tract Reticulospinal tract Tectospinal tract Tectospinal tract Tectospinal tract Tectospinal tract Ventral corticospinal tract Ventral corticospinal tract Ventral corticospinal tract Ventral corticospinal tract Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

36 Motor System Patient Case 1/11 An 86-year-old African-American man suddenly develops weakness and numbness of his right arm and his speech becomes slurred. An 86-year-old African-American man suddenly develops weakness and numbness of his right arm and his speech becomes slurred. Over the next 30 minutes the weakness, numbness, and difficulty speaking become worse. Over the next 30 minutes the weakness, numbness, and difficulty speaking become worse. His hand is weak and clumsy, and when he looks at himself in the mirror, the right half of his face appears to sag. His hand is weak and clumsy, and when he looks at himself in the mirror, the right half of his face appears to sag. The man has hypertension, diabetes mellitus, hypercholesterolemia, a body mass index of 35 (BMI of 30 equals obesity), and leads a sedentary lifestyle. The man has hypertension, diabetes mellitus, hypercholesterolemia, a body mass index of 35 (BMI of 30 equals obesity), and leads a sedentary lifestyle. When seen in an emergency room 1 hour later, the right side of his face and arm are almost completely paralyzed and have severe sensory deficit. When seen in an emergency room 1 hour later, the right side of his face and arm are almost completely paralyzed and have severe sensory deficit. Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

37 Case Follow-Up 2/11 The man described in this case has sudden onset weakness and sensory loss in his right arm, slurred speech, and the right side of his face is drooping. The man described in this case has sudden onset weakness and sensory loss in his right arm, slurred speech, and the right side of his face is drooping. The most likely cause of these symptoms is stroke (sudden onset weakness, sensory loss, and impaired speech are warning signs of stroke). The most likely cause of these symptoms is stroke (sudden onset weakness, sensory loss, and impaired speech are warning signs of stroke). Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

38 Case Follow-Up 3/11 The most likely location of the lesion is the left cerebral hemisphere. The most likely location of the lesion is the left cerebral hemisphere. This is because longitudinal systems are crossed such that the left hemisphere controls movement and sensation of the right side of the body. This is because longitudinal systems are crossed such that the left hemisphere controls movement and sensation of the right side of the body. R L Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

39 Paresis and Spasticity (Stroke) 4/11 Hemiplegia (motor + sensory) impairment of one side of the body (longitudinal systems) Hemiplegia (motor + sensory) impairment of one side of the body (longitudinal systems) Domains affected: motor, sensory, speech, cognitive, affect Domains affected: motor, sensory, speech, cognitive, affect Outcome: functional deficits (activities of daily living, ADL) due to impairment/ loss of learned, willed, skilled movement Outcome: functional deficits (activities of daily living, ADL) due to impairment/ loss of learned, willed, skilled movement Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

40 Case Follow-Up 5/11 The most likely location of the lesion is the left cerebral hemisphere. The most likely location of the lesion is the left cerebral hemisphere. This is because longitudinal systems are crossed such that the left hemisphere controls movement and sensation of the right side of the body. This is because longitudinal systems are crossed such that the left hemisphere controls movement and sensation of the right side of the body. R L Click to animate Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

41 Case Follow-Up 6/11 The areas that control movement and sensation of the face and arm are located beside each other on adjacent banks of the central sulcus. Also these areas are perfused by the same artery (middle cerebral). Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

42 Case Follow-Up Weakness of the right face and arm were caused by occlusion of the middle cerebral artery supplying the precentral gyrus. Weakness = motor sign Click to animate UMN LMN Stroke Lost function Impairment 7/11 Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

43 Case Follow-Up Impaired sensation of the right face and arm were caused by occlusion of the middle cerebral artery supplying the postcentral gyrus. Impaired sensation = sensory sign Click to animate UMN LMN Stroke Lost function Impairment 8/11 Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

44 Case Follow-Up Because his speech was fluent and coherent, his slurred speech was due to weakness of facial muscles (Dysarthria) rather than lesion of the speech production center (Broca’s area, productive aphasia). Broca’s area UMN LMN Stroke Lost function Impairment 9/11 Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

45 Case Follow-Up 10/11 Clinical evaluation led to the diagnosis of ischemic infarction (stroke) because of cerebrovascular disease resulting from hypertension and diabetes mellitus. Etiology and location of the lesion were confirmed by imaging studies. CT MRI Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

46 Case Follow-Up 11/11 Because the patient was seen within 3 hours of the onset of the stroke, he was treated with tissue plasminogen activator (TPA) in an attempt to dissolve the clot in the middle cerebral artery. Because the patient was seen within 3 hours of the onset of the stroke, he was treated with tissue plasminogen activator (TPA) in an attempt to dissolve the clot in the middle cerebral artery. The attempt was successful, and the patient’s strength and sensation gradually returned to normal by the time of discharge the next day. The attempt was successful, and the patient’s strength and sensation gradually returned to normal by the time of discharge the next day. He was prescribed medications to control his hypertension, lower serum cholesterol and blood glucose. He was also instructed to begin a diet and regular exercise to help control his diabetes and obesity. He was prescribed medications to control his hypertension, lower serum cholesterol and blood glucose. He was also instructed to begin a diet and regular exercise to help control his diabetes and obesity. Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

47 The End © DM McKeough 2009 Last Viewed Last Viewed Motor System Motor System Exit Concept Map Concept Map

48 Dualisms in the Motor System What are the two subsystems that comprise the somatic motor system? What are the two subsystems that comprise the somatic motor system? Dorsolateral and ventromedial motor systems Dorsolateral and ventromedial motor systems What are the two prominent types of lower motor neurons? What are the two prominent types of lower motor neurons? Alpha and gamma Alpha and gamma What are the two sites where the cell bodies of lower motor neurons are located in the spinal cord? What are the two sites where the cell bodies of lower motor neurons are located in the spinal cord? Dorsolateral- and ventromedial LMN pools in the ventral horn Dorsolateral- and ventromedial LMN pools in the ventral horn


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