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

Somatic Motor SystemSomatic Motor System

MotorTracts

BrainstemMotor

Centers

System Controls 2Aspects of Movement

Spinal MotorCenters

VentromedialSystem

SomaticMotor

System

VoluntaryMovement

PatientCase Cortical

MotorCenters

Map of EssentialMap of EssentialConceptsConcepts DM McKeough

© 2009

Postural SetPostural Setandand

Limb ManipulationLimb Manipulation

Lesion Effects

MotorHierarchy

DorsolateralSystem

Motor SystemMotor 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 ViewedLast Viewed ExitExitConcept MapConcept Map

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 SystemSomatic Motor System

Motor Control System

Last ViewedLast Viewed Motor SystemMotor System ExitExitConcept MapConcept Map

Voluntary Movement Voluntary Movement Originates in the Brain Originates in the Brain 1/31/3

Spinal Cord(LMN)

Proprioceptors

Thalamus

S1Assoc CtxM1 (UMN)


http://rpiwww.mdacc.tmc.edu/se/anatomy/brain/gross_brain_anterior.jpg

Control of Voluntary Movement Control of Voluntary Movement 2/32/3

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

UMNLMN

Stimulus


UMN Termination 3/3UMN Termination 3/3 Vast majority (~90%) of Vast majority (~90%) of

UMN terminate on UMN terminate on interneuronsinterneurons that then that then connect to LMN connect to LMN (polysynaptic connection)(polysynaptic connection) Allows integrationAllows integration

Minority of UMN (~10%) Minority of UMN (~10%) make monosynaptic make monosynaptic connection with LMNconnection with LMN Pincer grip (most Pincer grip (most

precise prehension)precise prehension)

UMN

ReciprocalInhibition


Control of Voluntary Control of Voluntary MovementMovement

Independent limb manipulationIndependent limb manipulation Controlled via the Controlled via the dorsolateral motor system motor system

Posture and balancePosture and balance Controlled via the Controlled via the ventromedial motor systemmotor system

System comparison

In general, the MC system may be seen as having 2 independent systems concerned with controlling 2 primary aspects of movement:


Organization of the SystemOrganization of the System

Dorsolateral systemDorsolateral system: : dedicated to the control dedicated to the control of skilled (fractionated) of skilled (fractionated) movement of movement of contralateral limbs contralateral limbs (appendicular skeleton)(appendicular skeleton) Corticobulbar tractCorticobulbar tract Lateral corticospinal tract Rubrospinal tract


Serial and Parallel Processing Serial and Parallel Processing 1/31/3

MC system uses both serial and parallel processingMC system uses both serial and parallel processing Serial processing: 2 neuron system Serial processing: 2 neuron system

Upper Motor Neuron (Upper Motor Neuron (UMN): UMN): projects from higher motor projects from higher motor control center (cortex or brainstem) to lower motor center control center (cortex or brainstem) to lower motor center (spinal cord) (spinal cord)

Lower Motor Neuron (Lower Motor Neuron (LMNLMN): projects from the ventral horn ): projects from the ventral horn to the muscle to the muscle

Alpha LMNAlpha LMN: large diameter neuron that innervate skeletal : large diameter neuron that innervate skeletal (extrafusal) muscle (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 Beta LMN: intermediate diameter neuron that innervates both

extrafusal and intrafusal muscle fibers (extrafusal and intrafusal muscle fibers (- co-activation)- co-activation) Gamma LMNGamma LMN: small diameter neurons that innervate : small diameter neurons that innervate

intrafusal muscle fibers (static and dynamic) intrafusal muscle fibers (static and dynamic) ά


(+)(+)

(-)

DorsolateralMotorSystem

ProprioceptiveReflexConnections

2/32/3


Serial and Parallel Processing Serial and Parallel Processing 3/33/3

MC system uses both serial and parallel MC system uses both serial and parallel processingprocessing Serial processing: 2 neuron systemSerial processing: 2 neuron system Parallel processing: normal movement is the Parallel processing: normal movement is the

result of the result of the simultaneoussimultaneous output of output of bothboth systems systems Ventromedial system controls involuntary Ventromedial system controls involuntary

postural and balance reactions. postural and balance reactions. Postural anticipation of balance disturbance occurs Postural anticipation of balance disturbance occurs

firstfirst Dorsolateral system controls voluntary limb Dorsolateral system controls voluntary limb

manipulation manipulation Movement of extremities represents a perturbation to Movement of extremities represents a perturbation to

balancebalance


Cortical Motor Centers Cortical Motor Centers 1/51/5

Cortical Cortical Primary motor cortex Primary motor cortex

(Precentral gyrus, MI, Area 4)(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)


Association and Supplementary Motor AreasDesired outcome of the action (Goal)

Premotor AreaMovement strategy

Primary Motor AreaMotor plan/ execution

CerebellumTiming, coordination, motor learning

Function of the Various Motor Areas 2/5

Goal Strategy Plan Execution

How movement occurs


Somatotopic Organization 3/5

Motor Homunculus


Comparison of Motor and Sensory Homunculi 4/5


Homunculus 5/5


Brainstem Motor CentersBrainstem Motor Centers

Tectum

Tectospinal

BrainstemBrainstem TectumTectum Vestibular nucleiVestibular nuclei Reticular nuclei Reticular nuclei Basal gangliaBasal ganglia CerebellumCerebellum

Tectum


Spinal Motor Centers Spinal Motor Centers 1/21/2

Ventral horn is comprised Ventral horn is comprised of cell bodies of alpha of cell bodies of alpha and gamma lower motor and gamma lower motor neurons with somatotopic neurons with somatotopic organizationorganization

Dorsolateral LMN poolDorsolateral LMN pool: : controls voluntary controls voluntary movement of the movement of the extremities, particularly extremities, particularly the hands (manipulation), the hands (manipulation), receives UMN input form receives UMN input form dorsolateral systemdorsolateral system


Spinal Motor Centers Spinal Motor Centers 2/22/2

Ventromedial LMN Ventromedial LMN pool: controls the pool: controls the trunk (posture and trunk (posture and balance), receives balance), receives UMN input from UMN input from ventromedial ventromedial system system


Lateral Lateral CorticospinalCorticospinalTractTract

Click to animateClick to animate

Upper motor neuron

Pyramidal decussation

Lateral corticospinal tract

UMNLMN

Stimulus



Rubrospinal Rubrospinal TractTract

Upper motor neuron

Pyramidal decussation

Lateral corticospinal tract

UMNLMN

Stimulus


Central PathwaysCentral Pathways

Tectospinal

Ventromedial system: Ventromedial system: dedicated to the control dedicated to the control of posture and balanceof posture and balance Vestibulospinal tract Reticulospinal tract Tectospinal tract Ventral corticospinal tract


Lateral Vestibulospinal Lateral Vestibulospinal TractTract


UMNStimulus

Last ViewedLast Viewed Motor SystemMotor System

ExitExitConcept MapConcept Map

ReticulospinalReticulospinalTractTract


UMNStimulus

Last ViewedLast Viewed Motor System Motor System



Tectospinal TractTectospinal Tract

UMNStimulus




Ventral CorticospinalVentral CorticospinalTractTract

UMNStimulus



Comparison of Dorsolateral and Ventromedial Motor Systems

Dorsolateral SystemDorsolateral System Ventromedial SystemVentromedial System

FunctionFunction Skilled (fractionated) movement Skilled (fractionated) movement of contralateral limbsof contralateral limbs

Posture BalancePosture Balance

TractsTracts Crossed Crossed

Lateral corticospinal Lateral corticospinal

RubrospinalRubrospinal

CorticobulbarCorticobulbar

Crossed and uncrossed Crossed and uncrossed Vestibulospinal Vestibulospinal

Reticulospinal Reticulospinal

TectospinalTectospinal

Ventral corticospinalVentral corticospinal

Spinal Spinal projectionprojection

Lateral column Lateral column Ventral columnVentral column

Spinal Spinal terminationtermination

Dorsolateral lower motor neuron Dorsolateral lower motor neuron poolpool

Ventromedial lower motor Ventromedial lower motor neuron poolneuron pool

Body segmentsBody segments Distal limb segmentsDistal limb segments Trunk Proximal limb Trunk Proximal limb segmentssegments

MusclesMuscles (+) flexors ((+) flexors () extensors) extensors (+) extensors ((+) extensors () flexors) flexors


Posture and Manipulation Posture and Manipulation 1/31/3

Postural setPostural set Auto-regulation: ventromedial system sets Auto-regulation: ventromedial system sets

proprioceptors (muscle spindle, GTO, joint proprioceptors (muscle spindle, GTO, joint receptors) to automatically maintain position.receptors) to automatically maintain position.

Independent limb manipulationIndependent limb manipulation Movement command: dorsolateral system over-Movement command: dorsolateral system over-

rides postural system (resets proprioceptors) to rides postural system (resets proprioceptors) to produce independent limb manipulation.produce independent limb manipulation.


Postural SetPostural Set

Tectospinal tract

2/32/3


LimbLimbManipulationManipulation

3/33/3


Lesion Effects 1/3Lesion Effects 1/3

Gray matter lesionsGray matter lesions The body regions and functions served by The body regions and functions served by

affected cell bodiesaffected cell bodies


Lesion Effects Lesion Effects 2/32/3

White matter lesionsWhite matter lesions Interruption of the information transmitted Interruption of the information transmitted

along that tractalong that tract All effects are generalized below the lesion All effects are generalized below the lesion

levellevel


Involuntary Movement Involuntary Movement 3/33/3

S&S of Cerebellar lesions:S&S of Cerebellar lesions: Tremor on intention: proximal, Tremor on intention: proximal,

slowslow Ataxia: trunk or limb Ataxia: trunk or limb DysmetriaDysmetria DysdiadochokinesiaDysdiadochokinesia Hypotonia: proximal > distalHypotonia: proximal > distal Dysarthria (scanning speech Dysarthria (scanning speech

pattern)pattern)


Motor HierarchyMotor Hierarchy

MC system consists of 3 levelsMC system consists of 3 levels Highest levelHighest level: association cortex, : association cortex,

sensory, and motor areassensory, and motor areas Concern: select movement goal Concern: select movement goal

and strategyand strategy Middle levelMiddle level: BG, Cb, and : BG, Cb, and

brainstem motor centersbrainstem motor centers Concern: specifying spatial, Concern: specifying spatial,

temporal, and force parameters temporal, and force parameters of the motor planof the motor plan

Lowest levelLowest level: LMNs, motor plant, : LMNs, motor plant, FB about sensory consequences FB about sensory consequences of the movementof the movement

Concern: producing the Concern: producing the movement pattern and supplying movement pattern and supplying sensory FBsensory FB

S1

Click to Animate


Motor TractsMotor Tracts

Dorsolateral motor systemDorsolateral motor system Lateral corticospinal tract Rubrospinal tract

Ventromedial motor systemVentromedial motor system Vestibulospinal tract Reticulospinal tract Tectospinal tract Ventral corticospinal tract


Motor System Patient Case Motor System Patient Case 1/111/11

An An 86-year-old African-American man suddenly develops 86-year-old African-American man suddenly develops weakness and numbness of his right arm and his speech weakness and numbness of his right arm and his speech becomes slurred. becomes slurred.

Over the next 30 minutes the weakness, numbness, and Over the next 30 minutes the weakness, numbness, and difficulty speaking become worse. difficulty speaking become worse.

His hand is weak and clumsy, and when he looks at himself in 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 mirror, the right half of his face appears to sag.

The man has hypertension, diabetes mellitus, The man has hypertension, diabetes mellitus,

hypercholesterolemia, a body mass index of 35 (BMI of 30 hypercholesterolemia, a body mass index of 35 (BMI of 30 equals obesity), and leads a sedentary lifestyle. equals obesity), and leads a sedentary lifestyle.

When seen in an emergency room 1 hour later, the right side of When seen in an emergency room 1 hour later, the right side of his face and arm are almost completely paralyzed and have his face and arm are almost completely paralyzed and have severe sensory deficit. severe sensory deficit.


Case Follow-Up Case Follow-Up 2/112/11

The man described in this case has sudden The man described in this case has sudden onset weakness and sensory loss in his right onset weakness and sensory loss in his right arm, slurred speech, and the right side of his arm, slurred speech, and the right side of his face is drooping.face is drooping.

The most likely cause of these symptoms is The most likely cause of these symptoms is

stroke (stroke (sudden onset sudden onset weakness, sensory loss, weakness, sensory loss, and impaired speech are warning signs of and impaired speech are warning signs of stroke).stroke).



The most likely location of the The most likely location of the lesion is the left cerebral lesion is the left cerebral hemisphere.hemisphere.

This is because longitudinal This is because longitudinal systems are crossed such that systems are crossed such that the left hemisphere controls the left hemisphere controls movement and sensation of movement and sensation of the right side of the body.the right side of the body.

R L


Paresis and Spasticity (Stroke) Paresis and Spasticity (Stroke) 4/114/11

Hemiplegia (motor + sensory) impairment Hemiplegia (motor + sensory) impairment of one side of the body (longitudinal of one side of the body (longitudinal systems)systems)

Domains affected: motor, sensory, speech, Domains affected: motor, sensory, speech, cognitive, affectcognitive, affect

Outcome: functional deficits (activities of Outcome: functional deficits (activities of daily living, ADL) due to impairment/ loss of daily living, ADL) due to impairment/ loss of learned, willed, skilled movementlearned, willed, skilled movement



The most likely location The most likely location of the lesion is the left of the lesion is the left cerebral hemisphere.cerebral hemisphere.

This is because This is because longitudinal systems are longitudinal systems are crossed such that the left crossed such that the left hemisphere controls hemisphere controls movement and sensation movement and sensation of the right side of the of the right side of the body.body.

R L

Click to animate



• 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).


Case Follow-UpCase Follow-Up

Weakness of the right face and arm were caused by occlusion of the middle cerebral artery supplying the precentral gyrus.

Weakness = motor signClick to animate

UMNLMN

Stroke

Lost function

Impairment

7/117/11



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

Click to animate

UMNLMN

Stroke

Lost function

Impairment

8/118/11



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

UMNLMN

Stroke

Lost function

Impairment

9/119/11



Clinical evaluation led to the diagnosis of ischemic infarction Clinical evaluation led to the diagnosis of ischemic infarction (stroke) because of cerebrovascular disease resulting from (stroke) because of cerebrovascular disease resulting from hypertension and diabetes mellitus.hypertension and diabetes mellitus. Etiology and location of the lesion were confirmed by imaging Etiology and location of the lesion were confirmed by imaging studies.studies.

CT MRI



Because the patient was seen within 3 hours of the onset Because the patient was seen within 3 hours of the onset of the stroke, he was treated with tissue plasminogen of the stroke, he was treated with tissue plasminogen activator (TPA) in an attempt to dissolve the clot in the activator (TPA) in an attempt to dissolve the clot in the middle cerebral artery. middle cerebral artery.

The attempt was successful, and the patient’s strength The attempt was successful, and the patient’s strength and sensation gradually returned to normal by the time of and sensation gradually returned to normal by the time of discharge the next day. discharge the next day.

He was prescribed medications to control his He was prescribed medications to control his hypertension, lower serum cholesterol and blood glucose. hypertension, lower serum cholesterol and blood glucose. He was also instructed to begin a diet and regular He was also instructed to begin a diet and regular exercise to help control his diabetes and obesity.exercise to help control his diabetes and obesity.


Dualisms in the Motor SystemDualisms in the Motor System What are the two subsystems that What are the two subsystems that

comprise the somatic motor system?comprise the somatic motor system? Dorsolateral and ventromedial motor systemsDorsolateral and ventromedial motor systems

What are the two prominent types of lower What are the two prominent types of lower motor neurons?motor neurons? Alpha and gammaAlpha and gamma

What are the two sites where the cell What are the two sites where the cell bodies of lower motor neurons are located bodies of lower motor neurons are located in the spinal cord?in the spinal cord? Dorsolateral- and ventromedial LMN pools in Dorsolateral- and ventromedial LMN pools in

the ventral hornthe ventral horn

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

Documents

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