Descending Tracts

Question 1

What do the pyramidal motor pathways pass through?

Answer 1

The medullary pyramids

Question 2

What do pyramidal motor pathways control?

Answer 2

Voluntary movement

Question 3

When do pyramidal pathways finish development and complete myelination?

Answer 3

Around 17-18 years old

Question 4

Name the pyramidal tracts

Answer 4

Corticospinal tract

Corticobulbar tract

Question 5

How and where are the cell bodies of upper motor neurones organised in the corticospinal tract

Answer 5

Somatotrophically in the cerebral cortex

-motor homunculus can be formed

Question 6

Where do the upper motor neurones of the corticospinal tract travel?

Answer 6

From the cerebral cortex they converge to descend through the midbrain, pons and medulla, passing through the internal capsule

Question 7

What is the difference between the lateral and anterior corticospinal tract?

Answer 7

90% of fibres decussate to the contralateral side at the medulla to form the lateral corticospinal tract - pyramidal decussation

10% ipsilateral - form the anterior corticospinal tract

Question 8

Where do the lateral corticospinal tract neurones terminate?

Answer 8

In the ventral horn

• 70% synapse with interneurones
• 30% synapse with lower motor neurones

Question 9

Where do the fibres of the anterior corticospinal tract decussate?

Answer 9

At the vertebral level in the spinal cord, and then synapse with lower motor neurones

Question 10

What is the path of the corticobulbar tract?

Answer 10

Originates in the cerebral cortex
Descends through the internal capsule to the brainstem where fibres decussate
Terminate on contralateral cranial nerve motor nuclei in the midbrain, pons and medulla

Question 11

What does the corticobulbar tract do?

Answer 11

Controls muscles of facial expression and extra-ocular muscles

Question 12

Name the extrapyramidal pathways

Answer 12

Vestibulospinal tract
Reticulospinal tract
Rubrospinal tract
Tectospinal tract

Question 13

Function of the vestibulospinal tract?

Answer 13

Responsible for balance and posture to the rest of the body

Question 14

Course of the vestibulospinal tract?

Answer 14

Arises from the vestibular nucleus

Fibres do not decussate

Question 15

Path of the reticulospinal tract?

Answer 15

Fibres arise from the medulla
Descend bilaterally to all levels of the spinal cord
Decussate partially in the brainstem

Question 16

Function of the reticulospinal tract?

Answer 16

Facilitate extensor spinal reflexes

Question 17

Path of the rubrospinal tract?

Answer 17

Arises from neurones of the red nucleus
Decussate in the midbrain
Descends contralaterally in the spinal cord

Question 18

Function of the rubrospinal tract?

Answer 18

Facilitate flexor motor neurones

Inhibit extensor motor neurones

Question 19

Path of the tectospinal tract?

Answer 19

Arise from the tectum of the brain stem
Decussate within the brain stem
Terminate in upper cervical segments

Question 20

Function of the tectospinal tract?

Answer 20

Aids the directing of head movements in response to visual and auditory stimuli

Question 21

What is the hierarchical organisation of the motor system?

Answer 21

Cerebral cortex highest
Brainstem nuclei and cerebellum intermediate
Motor neurones of cranial and spinal nerves lowest

Question 22

What is hemiplegia?

Answer 22

When an arm and leg on one side are paralysed

Question 23

What is monoplegia?

Answer 23

When one limb is paralysed

Question 24

What is diplegia?

Answer 24

When both arms are paralysed

Question 25

What is paraplegia?

Answer 25

When both legs are paralysed

Question 26

What is quadriplegia?

Answer 26

Paralysis of all limbs

Question 27

What happens in amyltrophic lateral sclerosis?

Answer 27

Corticospinal tracts and ventral horn cells degenerate

-often begins in lower limbs and later involves upper limbs

Question 28

What does ALS result in?

Answer 28

Weakness and loss of control to muscles in the hand, trunks and lower limbs
Bladder and bowel function can become impaired due to loss of descending autonomic pathways

Question 29

What happens in Brown-Sequard syndrome?

Answer 29

Lateral hemisection of the spinal cord resulting in loss of sensation and motor function (paralysis and ataxia)

Question 30

What can cause Brown-Sequard syndrome?

Answer 30

Tumour
Trauma
Ischaemia
Infectious or inflammatory conditions

Classic cause is a stab wound

Question 31

What do patients with Brown-Sequard syndrome present with?

Answer 31

Ipsilateral spastic paralysis

Loss of fine touch and proprioception to ipsilateral side due to fasciculus gracilis and cuneatus

Loss of pain, temperature and pressure sensation to contralateral side due to spinothalamic tract

Question 32

Which tracts does anterior spinal artery syndrome affect and what does it result in?

Answer 32

Corticospinal tracts ?and dorsal columns
Motor paralysis
Impaired pain and temperature sensation

Question 33

What is syringomelia?

Answer 33

Development of a cyst/cavity around the central canal

Grows and spreads over time

Question 34

Which tracts does syringomelia affect and why? Symptoms?

Answer 34

Spinothalamic tract - decussates just ventral to central canal

Reduced temperature and pain sensation at the level of the lesion
Fine touch and proprioception also affected

Can affect motor system as it extends