1. بسم الله الرحمن الرحيم

2. MOTOR CORTEX & PYRAMIDAL TRACT

3. LEARNING OBJECTIVES Motor cortex and pyramidal tract:
-Describe the different motor areas
-How different part of the body are represented in motor cortex
-Have concept of motor homunculus
-Describe the functions of different motor areas with their role in voluntary movement
-Describe the origin and functions of pyramidal tract

4. Cerebrum Highly developed
Makes up about 80% of total brain weight (largest portion of brain)
Divided into 2 halves:
Right and Left Cerebral Hemispheres
Connected to each other by Corpus callosum
Inner core houses basal nuclei
Outer surface is highly convoluted cerebral cortex
caps inner core that houses basal nuclei
Highest, most complex integrating area of the brain
Plays key role in most sophisticated neural functions
Highest, most complex integrating area of brain
Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

5. Cerebral Cortex
Thin outer shell of gray matter that covers each hemisphere
Covers a thick central core of white matter
Organized into 6 well-defined layers
Layers are organized into functional vertical columns
Each half of cortex divided into 4 major lobes:
Occipital
Temporal
Parietal
Frontal
Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

6. Cerebral cortex Frontal lobe Occipital lobe Temporal lobe
Responsible for 3 main functions:
Voluntary motor activity
Speaking ability
Elaboration of thought
Occipital lobe
Carries out initial processing of visual input
Temporal lobe
Initial reception of auditory (sound) sensation
Parietal lobe
Receive and process sensory input
Somatosensory processing
Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

8. Motor cortex Primary motor cortex ( M1 ; Brodmann area 4)
Premotor area (PMA) and Supplementary motor area (SMA) (Brodmann area 6)
Note: All the three projects directly to the spinal cord via corticospinal tract.
Premotor and supplementary motor cortex also project to primary motor cortex and is involved in coordinating & planning complex sequences of movement (motor learning).

9. Cerebral Cortex Primary motor cortex
Located in frontal lobe and immediately in front of central sulcus in front of somatosensory cortex
Confers voluntary control over movement produced by skeletal muscles
Primarily controls muscles on the opposite side of the body
Damage to motor cortex on the left side of brain produce paralysis on right side
Motor homunculus
Depicts location and relative amount of motor cortex devoted to output to muscles of each body part

10. Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

11. Cerebral Cortex Supplementary motor area:
-Lies on inner surface of each hemisphere
in front of primary motor cortex
-Plays preparatory role in programming complex sequences of movement
-Complex patterns of movement:
Opening or closing hand
Lesion: will not produce paralysis but they interfere with
performance of more complex movements
Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

12. Premotor cortex Located on lateral surface of each hemisphere
In front of the primary motor cortex
Is important in orienting the body and arms
toward a specific target
Commands primary motor cortex to produce
appropriate muscle contraction for the desired movement, but it should be informed body’s
momentary position
It is also guided by sensory input from
post. parietal cortex

13. Posterior parietal cortex:
-Lies posterior to primary somatosensory cortex
When either of these areas is damaged, one can’t process complex sensory information to accomplish purposeful movement
ie: manipulating eating utensils

14. Cerebral Cortex Supplementary motor area Premotor cortex
Plays preparatory role in programming complex sequences of movement
Complex patterns of movement:
Opening or closing hand
Premotor cortex
Important in orienting the body and arms toward a specific target
Posterior parietal cortex
Lies posterior to primary somatosensory cortex
When either of these areas is damaged, one can’t process complex sensory information to accomplish purposeful movement
ie: manipulating eating utensils
Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

15. Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

17. Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

18. Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

19. Cerebral Cortex Primary areas of cortical specialization for language
Broca’s area
Governs speaking ability
Wernicke’s area
Concerned with language comprehension
Responsible for formulating coherent patterns of speech
Language disorders
Aphasias
Most of which result from strokes
Speech impediments
Caused by defect in mechanical aspect of speech
Weakness or incoordination of muscles controlling vocal apparatus
Dyslexia
Inappropriate interpretation of words
Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

20. Cerebral Hemispheres Left cerebral hemisphere
Excels in logical, analytic, sequential, and verbal tasks
Math, language forms, philosophy
Tends to process information in fine-detail way
Right cerebral hemisphere
Excels in nonlanguage skills
Spatial perception and artistic and musical talents
Views the world in a big-picture, holistic way
Normally, the 2 hemispheres complement each other
Left cerebral hemisphere dominance
Associated with “thinkers”
Right hemispheric skills dominate in “creators”
Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

21. Corticospinal tract(Pyramidal tract)

22. Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

23. Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

24. CORTICOSPINAL (PYRAMIDAL) TRACT

25. Alpha Motor Neuron (A & B)

26. Origin of corticospinal/corticobulbar tracts The neurons of these tracts are Pyramidal shaped
Primary motor cortex (M1;Broadmann area 4)
31%
Premotor cortex and supplementary motor cortex (Broadmann area 6)
29%
Parietal lobe (Broadmann areas 5 and 7) and primary somatosensory area (Broadmann areas 3,1,2) in the post central gyrus
40%

27. Corticospinal Tract (CST)
Origin – Sensory cortex, primary Motor Cortex, premotor & supplementary cortex
(40%) (31%) (29%)
Internal Capsule
Pons
Cerebral Peduncle (midbarain)
Medullary Pyramid
Pyramidal Decussation
(80%) of the fibres cross( lateral CST) & (20%) do not cross (Ventral CST)
Ant. Horn of spinal cord through a interconnection
α motor neuron of opposite side

28. FUNCTIONS
( The axial muscles are concerned with postural adjustments & gross movements and distal limb muscles mediate fine & skilled movements).
Lateral corticopinal tract controls primarily distal muscle which are finely controlling the skilled movements of thumb & fingers on the opposite side.
eg. Painting writing, picking up of a small object etc.

29. Loss of distal motor function in opposite side.
Effect of lesion:
Loss of distal motor function in opposite side.
Pure corticospinal tract lesion cause hypotonia instead of spasticity
The reason is that pure pyramidal tract lesion is very very rare, and spasticity is due to loss of inhibitory control of extrapyramidal tract.

30. Cerebral Cortex
Schematic Linking
of Various Regions
of the Cortex