Map of Essential Concepts System Controls 2 Postural Set Somatic and

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Presentation transcript:

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

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

Somatic Motor System 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 Motor Control System Last Viewed Motor System Concept Map Exit

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

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 Motor System Concept Map Exit

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

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

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

Serial and Parallel Processing 1/3 MC system uses both serial and parallel processing Serial processing: 2 neuron system 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 Alpha LMN: large diameter neuron that innervate skeletal (extrafusal) muscle Organized into small, medium, and large motor units 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) ά Last Viewed Motor System Concept Map Exit

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

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

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

Function of the Various Motor Areas 2/5 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 Goal Strategy Plan Execution How movement occurs Last Viewed Motor System Concept Map Exit

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

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

Homunculus 5/5 Last Viewed Motor System Concept Map Exit

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

Spinal Motor Centers 1/2 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 Last Viewed Motor System Concept Map Exit

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

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

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

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

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

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

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

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

Comparison of Dorsolateral and Ventromedial Motor Systems Dorsolateral System Ventromedial System Function Skilled (fractionated) movement of contralateral limbs Posture Balance Tracts Crossed Lateral corticospinal Rubrospinal Corticobulbar Crossed and uncrossed Vestibulospinal Reticulospinal Tectospinal 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 Motor System Concept Map Exit

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

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

Limb Manipulation 3/3 Last Viewed Motor System Concept Map Exit

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

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

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

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

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

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. 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. 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. Last Viewed Motor System Concept Map Exit

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 most likely cause of these symptoms is stroke (sudden onset weakness, sensory loss, and impaired speech are warning signs of stroke). Last Viewed Motor System Concept Map Exit

Case Follow-Up 3/11 R L 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. Last Viewed Motor System Concept Map Exit

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

Case Follow-Up 5/11 R L 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. Click to animate Last Viewed Motor System Concept Map Exit

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 Motor System Concept Map Exit

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

Case Follow-Up 8/11 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 UMN LMN Stroke Lost function Impairment Click to animate Last Viewed Motor System Concept Map Exit

Case Follow-Up 9/11 Broca’s area 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). UMN LMN Stroke Lost function Impairment Last Viewed Motor System Concept Map Exit

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 Motor System Concept Map Exit

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. 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. Last Viewed Motor System Concept Map Exit

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

Dualisms in the Motor System What are the two subsystems that comprise the somatic motor system? Dorsolateral and ventromedial motor systems What are the two prominent types of lower motor neurons? Alpha and gamma 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