Descending Tracts

Question 1

Give a general statement about the pyramidal tracts.

Answer 1

Originate in the cerebral cortex, carrying motor fibres to the spinal cord and brain stem. They are responsible for the voluntary control of the musculature of the body and face

Question 2

Give a general statement about the extra-pyramidal tracts.

Answer 2

Originate in the brain stem, carrying motor fibres to the spinal cord. They are responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion

Question 3

All the neurones of the descending motor system are classed as what?

Answer 3

Upper motor neurones

Question 4

The Pyramidal tracts are split in two. Name them and what they supply.

Answer 4

Corticospinal tracts - supplies the musculature of the body

Corticobulbar tracts - supplies the musculature of the head and neck

Question 5

From what areas does the corticosinal tract get input from?

Answer 5

Primary motor cortex
Premotor cortex
Supplementary motor area
Somatosensory area

Question 6

What area doe the neurones of the corticospinal tract descend through? Why is this clinically significant?

Answer 6

Internal capsule
Particularly suscetible to copression from haemorrrhagic bleeds known as a “capsular stroke”. This could cause a lesion of th descending tracts.

Question 7

After the internal capsule, where do the neurones of the corticospinal tract course?

Answer 7

Through the crus cerebri of the midbrain, pons and into the medulla.

Question 8

What happens to the tract at the most inferior part of the medulla?

Answer 8

It splits in 2;
lateral corticospinal tract
anterior corticospinal tract

Question 9

Do the fibres from the anterior or lateral corticospinal tracts decussate?

Answer 9

Lateral

Question 10

The anterior corticospinal tract terminates where?

Answer 10

Ventral horn of cervical and upper throacic segmental levels

Question 11

The lateral corticospinal tract terminates where?

Answer 11

Ventral horn at all segmental levels

Question 12

The corticoulbar tract start and finish where?

Answer 12

Arise from the lateral aspect of the primary motor cortex, pass thorugh into the brain stem and terminate/synapse on the motor nuclei of the cranial nerves. LMN carry the motor signals to the muscles of the face and neck

Question 13

Do the majority of corticobulbar fibres innervate the motor neurones bilaterally or unilaterally?

Answer 13

Bilaterally

Question 14

What are the exceptions to the corticobulbar tract terminating bilaterally and terminate contralaterally?

Answer 14

Facial nerve (CNVII)
Hypoglossal nerve (CNXII)

Question 15

How many extra-pyramidal tracts are there? Name them.

Answer 15

4
Vestibulospinal 
Reticulospinal 
Rubrospinal 
Tectospinal

Question 16

Where do the medial and lateral vestibulospinal tracts arise from?

Answer 16

vestibular nuclei

Question 17

Do the vestibulospinal tracts remain ipsilateral when conveying this information to the spinal cord or do they decussate?

Answer 17

Remain ipsilateral

Question 18

What are the functions of the medial andlateral vestiulospinal tracs?

Answer 18

Control balance and posture by innervating the “anti-gravity” muscles (flexors of the arm and extensors of the leg), via LMNs.

Question 19

What is the function of the medial reticulospinal tract? Where does it arise from?

Answer 19

Arises from the pons. It facilitates voluntary movements, and increases muscle tone.

Question 20

Where does the lateral reticulospinal tract arise from and what is its function?

Answer 20

Arises from the medulla. It inhibits voluntary movements, and reduces muscle tone.

Question 21

The rubrospinal tracts arise from where?

Answer 21

The red nucleus (a midbrain structure)

Question 22

What is the course of the rubrospinal tracts?

Answer 22

As fibres emerge from the red nucleus, they decussate (cross over to the other side of the CNS), and descend into the spinal cord. Thus, they have a contralateral innervation.

Question 23

What is the function of the rubrospinal tracts?

Answer 23

Thought to play a role in the fine control of hand movements

Question 24

The tectospinal tracts begin where?

Answer 24

Superior colliculus of the midbrain

Question 25

What is the course of the tectospinal tract?

Answer 25

The neurones then quickly decussate after arising fromthe superior colliculi, and enter the spinal cord. They terminate at the cervical levels of the spinal cord.

Question 26

What is the function of the tectospinal tracts?

Answer 26

Coordinates movements of the head in relation to visual stimuli.

Question 27

What are the cardinal signs of an UMN lesion?

Answer 27

Hypertonia – an increased muscle tone
Hyperreflexia – increased muscle reflexes
Clonus – involuntary, rhythmic muscle contractions
Babinski sign – extension of the hallux in response to blunt stimulation of the sole of the foot
Muscle weakness