CorticalControl of Motor Activity- Corticospinal Tract Flashcards
List 3 Major Types of Movements
1) Reflexes
2) Automatic Postural Adjustments
3) Voluntary
Define: Reflexes
Stereotyped responses to stimuli
Characteristics of voluntary movements
1) Goal oriented
2) Internally generated
3) Improve with practice
What is at the top of the motor hierarchy
cerebral cortex
Which is the most important pathway for voluntary movement
The cerebrospinal tract
How many neurons does the corticospinal tract have ?
1, the UMN. This projects to LMN in the ventral horn of all levels of the spinal cord
What is the UMN route
Cerebral Cortez-> Corona radiata-> Internal Capsule (posterior limb) -> Crus cerbri -> Ventral Pons -> Medullary pyramid (Pyramidal decussation) -> Lateral funiculus
What is the somatotopical organization of the primary motor cortex
The lower limbs are most medial, as you move laterally -> upper limbs, face, mouth, tongue
What is the relevance of the MCA
The MCA is the blood supply to the lateral corticex, so it is responsible for both motor and sensory cortices.
A stroke in the upper MCA will affect the upper body.
A stroke in the lower MCA will affect the face and possibly cause aphasia.
What is the relevance of the ACA
It supplies the medial humunculus. A stroke in the ACA wil affect the lower limbs
Is the corona radiata somatotopically organized also ?
Yes
Significance of the internal capsule
The Corona Radiata converges here. So if there is an insult here it will affect much more than a single diffuse area affected by an isolated injury in The Corona Radiata
What track runs through the middle of the crus cerbri
The crus cerbri is located in the midbrain. The corticospinal tract runs through the middle of it.
Where is the tectum
It is in the midbrain only. It is posterior to the cerebral aqueduct and the colliculi
How close will the neurons of the cst be in the pons
They will be very broken up in the pons
How will the CST look in the medulla
The tracts of the CST will be very consolidated in the medulla. They will decussate at the medullary pyramids
Where does the CST travel once in the spinal cord ?
It travels in the lateral funiculus so the lateral spine.
What is the somatotopy of the lateral funiculus
The axial muscles will be more medial and the distal muscles or extremities will be more lateral
A lesion in the upper brainstem or internal capsule or the cortex will result in what type of lesion ?
A contralateral motor lesion
A lesion in the spinal cord will result in what type of deficit
An ipsilateral lesion since the decussation already took place at the medullary pyramids
What are some symptoms of injury to the lateral cortico-spinal tract ?
Loss of fractionated movement. So manual dexterity and precision will be gone
Symptoms of UMN cortico-spinal tract ?
Contralateral paresis or paralysis Spasticity Hyperreflexia Babinski sign Clonus
More symptoms of UMN lesion on one side
The unaffected side will try to move to compensate for teh loss in the injured side. For example unaffected wrist will attempt to move to compensate for affected wrist.
A lesion in the midbrain is associated with what ?
Weber’s syndrome:
- Contralateral body deficits
- Ipsilateral eye deficits with movement, ptosis and abscent light reflex via EW