Corticospinal Tract Flashcards
What is the function of the corticospinal tract?
Motor information to muslces of the trunk and limbs
Voluntary movement of skeletal muslce
Which kind of pathway is the corticospinal tract and why
It is a pyramidal pathway and this is because it is a voluntary pathway and passes crosses the pyramids on the surface of the medulla
The UMN originate from the cerebral cortex, what are the three locations which the axons leave from?
Primary motor cortex, supplementary motor cortex and premotor cortex
Why do some axons leave from the sensory cortex?
This is for the up-regulation of proprioception and the suppression of pain
What is the name of the cerebral white matter in the brain
Corona radiata
Whereabouts in the internal capsule does the corticopsinal tract pass?
It passes through the posterior limb of the internal capsule
Which two structures does the internal sit in between
The thalamus and the basal ganglia
Once the axons have entered the brainstem what happens at the level of the pyramids of the medulla in the corticospinal tract
Once they pass through the cerebral crus(midbrain) through pons into the medulla
- 85% of the fibres cross ( pyramidal decussation)
This 85% now become the lateral corticopspincal tract which is the tract of white matter now running in the lateral furniculus of the spinal cord
How is the anterior corticospinal tract formed and what is its function?
The remaining 15% of the UMN which do not cross the medulla become the anterior corticospinal tract, they run in the anterior furniculus
They are innervation to the trunks
Where does the crossing take place in the anterior corticospinal tract
At spinal cord at segmental level
Once crossing has taken place where does the UMN synapse, and where does it go
The UMN neuron then goes onto synapse with a LNM in the ventral horn of the spinal cord which then leaves the spinal cord via the ventral root to form peripheral nerves which will supply the musculature of the body
Which type of neurons are involved in pyramidal pathways?
Alpha motor neurons
Which kinds of neurons are involved in extra-pyramidal pathways and what is this pathways function
Alpha motor and gamma neurons
It is essentially the background work to keep us stable (balance), it makes our movements fluid and ensures no delay
What is the function of gamma neurons
They provide a baseline so that we dont get jerky movements, they have a knowledge of smooth movement
What is rediness potential
Measure of activity in motor cortex and supplementary motor areas of the brain leading up to voluntary movement
A lesion affecting corticopsinal fibres in the LEFT side of the ventral pons impairs voluntary moment of the arm and leg on which side and why
RIGHT SIDE
This is because injury ABOVE the pyramidal decussation leads to contralateral motor effects
A lesion affecting the cervical spinal cord on the left side impairs voluntary movement of the limbs on which side and why?
LEFT side
This is because injury below the pyramidal decussation will result in ipsilateral motor deficits.
What are the some symptoms of an UMN lesion and why does this happen?
Spastic paralysis, no significant muscle atrophy, hyperflexxia and hypertonia. Postive babinski result
This is because in UMN lesion - gamma is activated to the max, too much of everything nothing is controlled
What are the symptoms of an LMN lesion
Flaccid paralysis, significant atrophy and wasting, fasciculations, no maintenance of muscle tone
This is because the alpha motor neurone innervating the muscles is dead and the gammas are also disrupted making the muscles soft
In a lesion the UMN symptom is spastic (central) paralysis whereas in LMN the paralysis is flaccid (peripheral), why is this
This is due to the iinhibatoy effects that UMNs have on LMNs
In the absence of upper control the lower motor neuron exhibits a hyperactivity
While a lesion in the LMN will cause interruption to a skeletal muscle tonus control
