motor system 1

8/3/2019 Motor System 1

1/34

MOTOR SYSTEM IMOTOR SYSTEM I


2/34

idea

Cortical

associationarea

Basal

ganglia

Lateral

cerebellum

Premotor, supplementary

motor and motor cortex

Intermediate

cerebellum

musclesBrain stem

Plan Execute

Spinal cord


3/34

NEURAL AREAS THAT CONTROL

MOTOR FUNCTION

A. CEREBRAL CORTEX

B. BASAL GANGLIA

C. CEREBELLUM

D. BRAINSTEM

E. SPINAL CORD


4/34

I. CEREBRAL CORTEX

MOTOR CORTEXanterior to the central sulcus occupies

approximately the posterior 1/3 of the

frontallobeTHREE SUB AREAS

A. PRIMARY MOTOR AREA

B. PREMOTOR AREAC. SUPPLEMENTARY MOTOR AREA


5/34


6/34

A. Primary MotorArea

CorticalEff

erent Zones orMotor Homunculus


7/34

Posterior Parietal

Cortex

(Somatic Sensory

area I and II)

producedalso motor

responses

projects to the premotor

areaand supplementary

area


8/34

B. PremotorArea

receives a major input from the posterior

parietal cortex and its output influences

chiefly medialdescending pathway.

concerned with setting posture at the

start ofa planned complex movement.


9/34

C. Supplementary MotorArea

cause complex contraction that is usually

bilateral

needs stronger electrical stimulus to cause

contractionbelieved to be concerned with mental

rehearsal ofa planned movement.


10/34

Some other specialized corticalareas that

control motor function:

a) Brocas area

b) Voluntary Eye Movement Field /Frontal Eye Field

c) Head Rotation Area

d) Area for Hand Skills


11/34


12/34

II. BASAL GANGLIAComponents:

a) caudate nucleusstriate body

b) putamen

lentiform nucleus

c) globus pallidus

Functionally related nuclei;

a) subthalamic nucleus (diencephalons)

b) substancianigra (midbrain)c) ventralanterior (VA)and ventrallateral (VL)

thalamic nuclei


13/34


14/34


15/34

cortex

Striatum

(acetylcholine)

Substancia nigra

Pars compacta

thalamus

Supplementary motor area

Globus pallidus Substancia nigraInternal segment pars reticulata

Globus palliodus

External segment

Subthalamic nucleus

GABA/substance P

dopamine

glutamateGABA/enkephalin

glutamateGABA glutamate

glutamate

GABA


16/34

Two Important Pathways

A) Direct Pathwayenhance motoractivity

controls rapid motoractivity

decreasedactivity will cause hypokinetic behavior.

B) Indirect Pathwayreduce motoractivity

controls slow motoractivity

decreasedactivity will cause hyperkineticbehavior


17/34

Two General Types ofDisordersA. HYPERKINETIC BEHAVIOR

a) Choreacaused byalesion in the striate body.

characterized by rapid, involuntarydancing movements.

b) Ballismus (Hemiballismus)

caused byalesion in the subthalamic nucleus.

characterized by involuntaryand violent flailing movementsof the limbs.

c) Athetosis

caused byalesion in the lenticularnucleus.

characterized bya slow, writhing movement of wormlikecharacter that appears chiefly in fingers and wrist.


18/34

B. HYPOKINETIC BEHAVIOR

a) Akinesia

difficulty in initiating movement and

decreased spontaneous movement

b) Bradykinesia

slowness in initiating movement


19/34

III. CEREBELLUM

helps regulate movements and postureandalso involved in some forms of motor

learning.

its major role is for motor coordination

(rate, range, force anddirection of the

movement)

deep cerebellarnuclei dentate nucleus

emboliform

globose

fastigialnuclei


20/34


21/34


22/34

Anatomic Division

A. Anteriordivision

B. Posteriordivision

C. Flocculonodulardivision

FUNCTIONAL DIVISION

A. Vestibulocerebellum (Archicerebellum)

B. Spinocerebellum (Paleocerebellum)

C. Cerebrocerebellum / Corticocerebellum(Neocerebellum)


23/34


24/34

A. Vestibulocerebellum (Archicerebellum)

corresponds primarily to theflocculonodularlobe.

dominated by vestibular input.

regulates eye movement, stance andgait. (equilibrium andlearning induced

changes in VOR*


25/34

B. Spinocerebellum (Paleocerebellum)corresponds primarily to the intermediate

portion.

receives proprioceptive and spinal cord

input.

regulates truncaland proximallimbs

movements (maintenance of posture)

it smoothes and coordinates movementsthat are ongoing


26/34

C. Corticocerebellum or Cerebrocerebllum

(Neocerebellum)

corresponds to the lateral portion.

receives indirect input from the cerebrum

by way pontine nuclei.concerned with motor planningand

programming


27/34

Motor Dysfunctions in Cerebellar

Diseaseincoordination, malequilibrium and

problems with muscle tone.

AtaxiaDysmetria / Pastpointing

Dysdiadochokinesia/ Adiadochokinesia

Domposition of movement

DysarthriaIntension tremors


28/34

Malequilibrium

Disturbances in muscle tone

Astasia - loss of muscle endurance

Asthenia - loss of muscle strength

Atonia/Hypotonia - absent /

diminished muscle tone


29/34

IV. BRAINSTEM

composed of midbrain, pons and medulla.primarily concerned with the control ofaxialand

proximal musculature (antigravity muscles)

Brainstem Pathwaysreticulospinal pathway

vestibulospinal pathway Medialdescending

tectospinal pathway Pathway

rubrospinal pathway - Lateral DescendingPathway


30/34

V. SPINAL CORD


31/34

Cells in the anterior horn

motorneuron

innervates extrafusal muscle fibers.

motorneuron

innervates intrafusal muscle fibers

interneurons

most abundant

inhibitory or excitatory


32/34

DESCENDING PATHWAYS

A) Corticobulbar Tract

B) Corticospinal Tract

most important output pathway from the

cerebral cortex.

origin:

30% - primary motorarea

30% - premotorarea40% - posterior parietalarea


33/34

Lateral Corticospinal Tract

constitute 80% of the fibers.

fibers cross at the midline of the medullary

pyramid.

occupies the lateral portion of the spinalcord.

concerned with the control ofdistal

musculature (hands and fingers).

mediate fine and skilled movements.

includes rubrospinal tract.


34/34

Medial / Anterior / Ventral Corticospinal

Tract

constitute 20% of the fibers.fibers do not cross at the midline of the medullary

pyramid.

occupies the ventral (anterior)and medial portionof the spinal cord.

concerned with the control ofaxialand proximalmusculature (trunk and proximallimbs)

projection fibers of medial system are mostlycoming from the premotor cortex.

mediate posturaladjustments andgross

movementsincludes reticulospinal, vestibulospinaland

tectospinal

motor system 1

Documents