3. Anatomy of corticospinal tract

Question 1

What is corticospinal tract?

Answer 1

A part of descending, pyrimidal tracts of CNS. Motor signals from brain are sent to lower neurons. Affect mus. of the body.

Question 2

Anatomy at the level 1

Answer 2

Originate in cerebral cortex: Layer V pyrimidal cells of neocortex

• Prim. motor cortex: Precentral gyrus, Brodmann area 4, 30%
• Premotor cortex + Supplementary motor area: 30%
• Somatosensory area + parietal lobe & cingulate gyrus: 40%, responsible for regulating activity of ascending tracts

Question 3

Anatomy at the level 2

Answer 3

Neurons converge & descend through post. limb internal capsule

Question 4

Anatomy at the level 3

Answer 4

Through crus cerebri (cerebral peduncle in the midbrain) –> pons

Question 5

Anatomy at the level 4

Answer 5

Through medulla along w/corticobulbar tract, creating 2 pyrimidal bumps on each side. Corticospinal tract divides into lat. & ant.:

• LCT: Decussate 80%, 10% cross at their corresponding place in spinal cord
• ACT: Remain ipsilateral, 10%

Question 6

Anatomy at the level 5 (last)

Answer 6

LCT descend into spinal cord & terminate in ventral horn & synpase w/LMN. ACT decussate & terminate in ventral horn of cervical & upper thoracic segmental levels