The document discusses the motor system and descending motor pathways. It identifies the major cortical inputs to the motor pathways as the primary motor cortex, premotor cortex, supplementary motor area, and cingulate motor area. It describes the lateral descending pathways of the corticospinal, rubrospinal, and reticulospinal tracts which control fine voluntary movement and distal muscles. The medial pathways of the anterior corticospinal, tectospinal, and vestibulospinal tracts control postural and reflex movement and proximal/axial muscles. It traces the path of the lateral corticospinal tract from the motor cortex through the brainstem and spinal cord.

1. Motor system!!
DR. Shittu LAJ.

2. Objectives
• Identify major cortical inputs to the
motor pathways
• List the descending pathways
– differentiating characteristics
• Trace the lateral corticospinal tract
• Identify sites of decussation

4. Descending Pathways
• Lateral Systems
– Corticospinal
• Lateral
– Rubrospinal
• Medial systems
– Corticospinal
• Anterior
– Reticulospinal
– Tectospinal
– Vestibulospinal
α α

5. • Lateral systems
– Fine voluntary movement
– Distal muscles
Medial systems
Postural and reflex movement
Proximal and axial muscles

7. Motor Cortex
• M1 = Primary
– precentral gyrus
• SMA =
supplementary
– anteromedial
• Premotor Area
– Anterolateral
• Cingulate Motor

9. Pierre Paul Broca (1824-1880)
From an engraving after a
portrait (1867) by LaFosse.

10. 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

11. Lateral Corticospinal Tract
– M1 (and premotor cortex)
– Centrum Semiovale
– Corona Radiata
– Internal Capsule -- posterior limb
– Cerebral Peduncle
– Pontine Tegmentum
– Medullary Pyramid

12. Brain ImagingTransverse (Axial) Imaging

13. 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

14. Primary Motor & Sensory
Cortex
• Precentral Sulcus
– Primary Motor
• Postcentral Sulcus
– Primary Sensory
Roland
Motor
Sensory

15. Functional Imaging (fMRI)
Roland
What was this person doing?What was this person doing?

16. Wallerian Degeneration
• Motor Cortex Injury
• Degeneration of first
order motor neurons
• Outlines the
corticospinal tract

17. Precentral Gyrus

18. Corona Radiata

19. Pontine Tegmentum

20. Medullary Pyramid

24. Essential Points
• Identify major cortical inputs to the
motor pathways
– M1=primary motor cortex
– Premotor Cortex
– SMA=supplementary motor area
– Cingulate Motor Area

25. Essential Points
• List the descending pathways
– Lateral Corticospinal
– Anterior Corticospinal
– Rubrospinal
– Tectospinal
– Vestibulospinal
– Reticulospinal
– [Corticostriatal]
Direct cortex effect
Indirect cortex effect

26. Essential Points
• Differences
– Lateral Corticospinal
– Rubrospinal
– Anterior Corticospinal
– Tectospinal
– Vestibulospinal
– Reticulospinal
Distal muscles
Fine movement
Proximal and axial muscles
Gross and postural movement

27. 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

28. Essential Points
• Identify sites of decussation
– Lateral Corticospinal
– Anterior Corticospinal
– Rubrospinal
– Tectospinal
– Vestibulospinal
– Reticulospinal
Medullary Pyramid
Not Applicable
Midbrain Tegmentum
Midbrain
Not Applicable

29. Sagittal Imaging: Identify
regions

31. Brain ImagingTransverse (Axial) Imaging

32. Coronal Imaging
TENT