Notes on Corticospinal Tracts

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Origin of Fibres Entering the Corticospinal Tracts:

1. Premotor area.

2. Motor cortex (precentral gyrus - area 4).

3. Somatic sensory cortex.

4. Superior region of parietal lobule.

Passage of Corticospinal Tracts:

From the somato-motory cortex (Betz cells) through the corona radiata and internal capsule, via the brainstem, crus of the midbrain and pons to the medulla oblongata. In the medulla oblongata the fibres are termed the pyramidal tract.

Function of corticospinal or pyramidal tract:

The chief function is control of fine voluntary movements (i.e. writing and doing up a button).

Connections and Divisions of the Corticospinal Tracts:

1. Cortico-nuclear branches to cranial nuclei (affecting face, jaw, tongue).

2. At the pyramidal decussation 80% if the fibres pass in the lateral corticospinal tract and about 15% in the anterior corticospinal tract.

3. About 5% of fibres remain uncrossed and descend in the ipsilateral corticospinal tract.

4. High damage to the corticospinal tracts results in Upper Motor Neuron Disease (i.e. stroke).

Other Functions of the Descending Tracts:

1. Reticulospinal:

Locomotion and postural control. Control of the proximal parts of the limbs and trunk and in walking and running.

2. Tectospinal:

Function uncertain in man but is postulated to be associated with head and trunk orientation following visual and auditory stimuli.

3. Vestibulospinal:

Maintenance of centre of gravity between the feet. Reflexes that alter body position in relation to movements of the head.

4. Raphespinal:

Modulation of sensory transmission.

5. Aminergic:

Inhibit sensory and facilitate motor neurons.

6. Central Autonomic Pathways:

Sympathetic pathways are associated with baroreceptor - reflexes, and the parasympathetic pathways, bladder and rectal function.

Chapters on Spinal Cord:

1. Anatomy of the Spinal Cord
2. Ascending Spinal Tracts
3. Blood Supply of Spinal Cord
4. Notes on Corticospinal Tracts
5. Cross Section of Spinal Cord
6. Descending Spinal Tracts
7. Grey Matter of Spinal Cord
8. Summary of Spinal Nerves

Additional Reading:

Basic Neurology

1. Peripheral Nervous System
2. Central Nervous System
3. The Ventricular System
4. The Spinal Cord
5. The Brain Stem
6. The Cerebellum
7. Visual Pathways
8. Diencephalon
9. Basal Ganglia
10. Cerebral Cortex
11. Sleep Disorders
12. Autonomic Nervous System
13. Cranial Nerves and Parasympathetic Ganglia
14. Cells of the Nervous System
15. Cerebrospinal fluid
16. Additional short notes on Cerebrum
17. Functions and Diseases of Cerebrum
18. Subcortical Grey Matter
19. Notes on The Spinal Cord
20. Regulation of Heart Rate by Autonomic Nervous System
21. Action Potentials, Axon Conduction, and Neuromuscular Junction
22. Types of Seizures
23. What is a Cough Reflex?
24. Notes on Congenital Prosopagnosia
25. Findings in Parkinson's Disease
26. Types of Heat Strokes
27. Types of Strokes
28. What is Benign Intracranial Hypertension?
29. What is Cauda Equina Syndrome?
30. Cranial Nerve Locations in Brain Stem
31. What is a Cluster Headache?
32. What is a Subarachnoid Hemorrhage?
33. What is a Tension Headache?

Neurology Videos

1. Video of Neurology Examination in a Clinical Setting

Medical Images

Useful Medical Images & Diagrams (link opens in a new window)

Related Topics

1. Nervous System Disorders
2. Histology of Nervous Tissue
3. Cranial Nerve Reflexes
4. Motor System Examination

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