Motor system!!

DR. Shittu LAJ.

Objectives

• Identify major cortical inputs to the motor pathways

• List the descending pathways– differentiating characteristics

• Trace the lateral corticospinal tract

• Identify sites of decussation

Descending Pathways

• Lateral Systems– Corticospinal

• Lateral

– Rubrospinal

• Medial systems– Corticospinal

• Anterior

– Reticulospinal

– Tectospinal

– Vestibulospinal

α α

• Lateral systems– Fine voluntary movement– Distal muscles

Medial systemsPostural and reflex movementProximal and axial muscles

Motor Cortex

• M1 = Primary– precentral gyrus

• SMA = supplementary– anteromedial

• Premotor Area– Anterolateral

• Cingulate Motor

Pierre Paul Broca (1824-1880)

From an engraving after a portrait (1867) by LaFosse.

Lateral Corticospinal Tract

• Most direct pathway– …but 50% of axons → cerebellum via pons

• Voluntary motor control– fine movement/distal muscles

• Monosynaptic to hand

– gross movement• synapse on spinal interneurons>50% of CS axons

Lateral Corticospinal Tract

– M1 (and premotor cortex)– Centrum Semiovale

– Corona Radiata– Internal Capsule -- posterior limb– Cerebral Peduncle– Pontine Tegmentum– Medullary Pyramid

Brain ImagingTransverse (Axial) Imaging

Central (Rolandic) Sulcus

• Its more posterior than you’d expect

• Pearl:follow the superior frontal sulcus back to the precentral sulcus

• Remember: All anatomy is variable

Roland

Primary Motor & Sensory Cortex

• Precentral Sulcus– Primary Motor

• Postcentral Sulcus– Primary Sensory

Roland

Motor

Sensory

Functional Imaging (fMRI)

RolandWhat was this person doing?What was this person doing?

Wallerian Degeneration

• Motor Cortex Injury• Degeneration of first

order motor neurons• Outlines the

corticospinal tract

Precentral Gyrus

Corona Radiata

Pontine Tegmentum

Medullary Pyramid

Essential Points

• Identify major cortical inputs to the motor pathways– M1=primary motor cortex– Premotor Cortex– SMA=supplementary motor area

– Cingulate Motor Area

Essential Points

• List the descending pathways– Lateral Corticospinal– Anterior Corticospinal– Rubrospinal– Tectospinal– Vestibulospinal– Reticulospinal– [Corticostriatal]

Direct cortex effect

Indirect cortex effect

Essential Points

• Differences– Lateral Corticospinal– Rubrospinal– Anterior Corticospinal– Tectospinal– Vestibulospinal– Reticulospinal

Distal musclesFine movement

Proximal and axial musclesGross and postural movement

Essential Points

• Trace the lateral corticospinal tract– M1 (and premotor cortex)– Centrum Semiovale– Corona Radiata– Internal Capsule -- posterior limb– Cerebral Peduncle– Pontine Tegmentum– Medullary Pyramid

Essential Points

• Identify sites of decussation– Lateral Corticospinal– Anterior Corticospinal– Rubrospinal– Tectospinal– Vestibulospinal– Reticulospinal

Medullary Pyramid

Not Applicable

Midbrain Tegmentum

Midbrain

Not Applicable

Sagittal Imaging: Identify regions

Brain ImagingTransverse (Axial) Imaging

Coronal Imaging

TENT