Descending tracts

Question 1

What are the two main groups of descending tracts?

Answer 1

Pyramidal - originate in cerebral cortex, pass through medullary pryamids of the medulla oblongata
Extra-Pyramidal - Originate in the brainstem

Question 2

What is the function of the pyramidal descending tracts?

Answer 2

Voluntary control of musculature of the face and body

Question 3

What is the function of the extra-pyramidal descending tracts?

Answer 3

Involuntary and autonomic control of musculature eg muscle tone, balance and posture

Question 4

What is an upper motor neurone?

Answer 4

A neurone that has both its cell body and axon within the CNS

Question 5

What are the two pyramidal tracts?

Answer 5

Corticospinal

Corticobulbar

Question 6

What is the function of the Corticospinal tract?

Answer 6

Supplies musculature of the body

Question 7

What is the function of the Corticobulbar tract?

Answer 7

Supplies musculature of the face

Question 8

What are the three main inputs for the Corticospinal tract?

Answer 8

Primary motor cortex
Premotor cortex
Supplementary motor area
Also somatosensory which regulates the ascending tracts

Question 9

What happens to the neurones of the Corticospinal tract immediately after leaving the cortex?

Answer 9

They converge and pass through the internal capsule Important as the internal capsule is particularly susceptible to compression from heamorrhagic bleeds

Question 10

Briefly, what is the path of the Corticospinal tract?

Answer 10

Leaves cortex, passes trough internal capsule, pass through crus cerebri, pons and then into medulla then split into anterior and lateral tracts

Question 11

What is the route of the anterior Corticospinal tract?

Answer 11

Descending ipsilaterally in the spinal cord

Decussate and terminate in the ventral horn of lower cervical/upper thoracic levels

Question 12

What is the route of the lateral Corticospinal tract?

Answer 12

Decussate and descend in the contralateral side of the spinal cord
Terminate in the ventral horn

Question 13

Briefly, what is the route of the Corticobulbar tract?

Answer 13

Arise in primary motor cortex (With inputs from Primary motor cortex, Premotor cortex and Supplementary motor area)
Fibres converge and pass through internal capsule
Terminate on the motor nuclei of the cranial nerves

Question 14

Most Corticobulbar tract fibres innervate bilaterally, which cranial nerves do not receive bilateral innervation?

Answer 14

Facial nerve has contralateral innervation

Hypoglossal nerve has contralateral innervation

Question 15

What are the four extra-pyramidal tracts?

Answer 15

Vestibulospinal
Reticulospinal
Rubrospinal
Tectospinal

Question 16

Which of the extra-pyramidal tracts decussate?

Answer 16

Rubrospinal
Tectospinal
Therefore innervate contralateral side

Question 17

Which of the extra-pyramidal tracts do not decussate?

Answer 17

Vestibulospinal
Reticulospinal
Therefore innervate ipsilateral side

Question 18

What is the function of the Vestibulospinal tracts?

Answer 18

Balance

Posture by innervating antigravity muscles

Question 19

Briefly, what is the route of the Vestibulospinal tract?

Answer 19

Arises in vestibular nucleus (Receives input from organs of balance)
Conveys balance information to ipsilateral spinal cord

Question 20

What are the two branches of the Reticulospinal tract?

Answer 20

Medial

Lateral

Question 21

What is the function of the Medial Reticulospinal tract?

Answer 21

Voluntary movement

Increases muscle tone

Question 22

Where does the Medial Reticulospinal tract originate?

Answer 22

In the Pons

Question 23

What is the function of the Lateral Reticulospinal tract?

Answer 23

Inhibits voluntary movement

Decreases muscle tone

Question 24

Where does the Lateral Reticulospinal tract originate?

Answer 24

In the Medulla

Question 25

Briefly, what is the route of the Rubrospinal tract?

Answer 25

Originates in the Red nucleus (Midbrain structure)
Decussate as emerge from nucleus
Travel down contralateral side of the spinal cord so contralateral innervation

Question 26

What is the function of the Rubrospinal tract?

Answer 26

Unsure, but thought to be fine hand movements

Question 27

Briefly, what is the route of the Tectospinal tract?

Answer 27

Begins in superior colliculus of the midbrain (Receives input from the optic nerves)
Decussate immediately and enter the spinal cord on the contalateral side
Terminate at cervical levels

Question 28

What is the function of the Tectospinal tract?

Answer 28

Co ordinates movements of the head in relation to visual stimuli

Question 29

Why are the pyramidal tracts vulnerable to damage?

Answer 29

They extend the whole length of the spinal tract without synapsing
They pass through the internal capsule which is a high risk area for haemorrhage

Question 30

What are the signs of damage to the Corticospinal tract?

Answer 30

Hypertonia
Hyperreflexia
Clonus
Babinski's sign
Muscle weakness
(On the contralateral side)

Question 31

What are the signs of damage to the Corticobulbar tract?

Answer 31

Mostly muscle weakness as there is bilateral innervation, However Facial nerve will have spastic paralysis of contralateral lower quadrant of the face
Hypoglossal nerve will have spastic paralysis on the contralateral side so tongue will point to contralateral side

Question 32

How are the extra pyramidal tracts most likely to be damaged?

Answer 32

Degenerative diseases
Tumours
Encephalitis (Inflammation of brain tissue)

Question 33

What are the signs of extra pyramidal tract damage?

Answer 33

Disorders of involuntary movement

Diskinesias