Corticospinal Tract

Question 1

What is the function of the corticospinal tract?

Answer 1

Motor information to muslces of the trunk and limbs

Voluntary movement of skeletal muslce

Question 2

Which kind of pathway is the corticospinal tract and why

Answer 2

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

Question 3

The UMN originate from the cerebral cortex, what are the three locations which the axons leave from?

Answer 3

Primary motor cortex, supplementary motor cortex and premotor cortex

Question 4

Why do some axons leave from the sensory cortex?

Answer 4

This is for the up-regulation of proprioception and the suppression of pain

Question 5

What is the name of the cerebral white matter in the brain

Answer 5

Corona radiata

Question 6

Whereabouts in the internal capsule does the corticopsinal tract pass?

Answer 6

It passes through the posterior limb of the internal capsule

Question 7

Which two structures does the internal sit in between

Answer 7

The thalamus and the basal ganglia

Question 8

Once the axons have entered the brainstem what happens at the level of the pyramids of the medulla in the corticospinal tract

Answer 8

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

Question 9

How is the anterior corticospinal tract formed and what is its function?

Answer 9

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

Question 10

Where does the crossing take place in the anterior corticospinal tract

Answer 10

At spinal cord at segmental level

Question 11

Once crossing has taken place where does the UMN synapse, and where does it go

Answer 11

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

Question 12

Which type of neurons are involved in pyramidal pathways?

Answer 12

Alpha motor neurons

Question 13

Which kinds of neurons are involved in extra-pyramidal pathways and what is this pathways function

Answer 13

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

Question 14

What is the function of gamma neurons

Answer 14

They provide a baseline so that we dont get jerky movements, they have a knowledge of smooth movement

Question 15

What is rediness potential

Answer 15

Measure of activity in motor cortex and supplementary motor areas of the brain leading up to voluntary movement

Question 16

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

Answer 16

RIGHT SIDE

This is because injury ABOVE the pyramidal decussation leads to contralateral motor effects

Question 17

A lesion affecting the cervical spinal cord on the left side impairs voluntary movement of the limbs on which side and why?

Answer 17

LEFT side

This is because injury below the pyramidal decussation will result in ipsilateral motor deficits.

Question 18

What are the some symptoms of an UMN lesion and why does this happen?

Answer 18

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

Question 19

What are the symptoms of an LMN lesion

Answer 19

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

Question 20

In a lesion the UMN symptom is spastic (central) paralysis whereas in LMN the paralysis is flaccid (peripheral), why is this

Answer 20

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