1.9 Descending Pathways

Question 1

What are the symptoms of lower motor neuron damage?

Answer 1

• Paralysis - loss of movement 
	• Paresis - weakness of affected muscles 
	• Loss of reflexes 
	• Loss of muscle tone 
Fibrillations and fasciculation

Question 2

Define distal and proximal musculature?

Answer 2

Distal musculature - controls fine movements e.g. fingertips - lateral
Proximal and axial musculature - controls postions - medial

Question 3

How many descending pathways are there, and what are they called?

Answer 3

5 
Lateral and anterior corticospinal
reticulospinal
rubrospinal 
tectospinal
vestibulospinal

Question 4

Explain the functions of each of these?

Answer 4

Lateral corticospinal - voluntary control ofdistal musculature
Anterior corticospinal - voluntary control of proximal vasculature
Reticulospinal - regulate flexor reflexes and initiate patterned activity such locomotion
Rubrospinal - Upper flexion
Tectospinal - visual stimuli and coordination
Vestibulospinal - balance and head movements etc.

Question 5

Explain the direct upper motor pathways…

Answer 5

Corticospinal tract;

Corticobulbar tract

Question 6

What can damage to these result in?

Answer 6

Damage result in Babinski sign; Paralysis, Paresis exclusively fine skilled movements
Segmental reflexes remain unaffected

Question 7

Explain the indirect upper motor pathways…

Answer 7

From brainstem nuclei to LMN

Question 8

Damage to these can result in what?

Answer 8

Damage result in spastic paralysis, hyperreflexia etc….

Question 9

Where does the lateral corticospinal tract decussate?

Answer 9

Rostral medulla - pyramid

Question 10

Where does does the anterior corticospinal tract decussate?

Answer 10

Spinal level

Question 11

With which nuclei are corticobulbar fibres associated with?

Answer 11

V, VII, XI & XII

Question 12

Which ones are bilateral and unilateral?

Answer 12

V &XI are bilateral

VII & XII are unilateral

Question 13

Are the muscles of the face below the eye innervated bilaterally or unilaterally?

Answer 13

Unilaterally

Question 14

What effects would an upper motor lesion in the corticobulbar tract have?

Answer 14

Facial Paralysis - contralateral below the eye

Question 15

What would a lower motor lesion in the same tract result in?

Answer 15

Facial Paralysis - ipsilateral whole face

Question 16

What is the pathway of the rubrospinal tract? What is its function?

Answer 16

Red nucleus - mesencephalon - decussates quickly - upper flexor activity

Question 17

Where does the tectospinal tract arise from?

Answer 17

Tectum - superior colliculus

Question 18

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

Answer 18

Reticular formation - midbrain - ipsilateral - locomotion and pain modulation

Question 19

Where does the vestibulospinal tract originate from and what is its function?

Answer 19

Vestibular nucleus - balance and coordination

Question 20

Explain the Babinski sign…

Answer 20

Fanning of toes - upper motor neurone damage (direct)

Question 21

Describe Decorticate Posturing…

Answer 21

Lesion above the red nucleus - including thalamus or internal capsule.
It involves the involuntary flexion of the upper extremeties in response to external stimuli - excess red nucleus influence. Arms are flexed and bent inwards, fists are clenched and feet are turned inwards.

Question 22

Explain Decerbrate Posturing…

Answer 22

Brainstem damage at or below the level of the red nucleus e.g, a pontine stroke or uncal herniation. It describes the involuntary extension of the upper extremities in response to external stimuli. the head is arched back, the arms are extended by the sides and rotated internally, the legs are extended and rotated internally the patient is rigid, with the teeth clenched

Question 23

Explain the structure of the internal capsule…

Answer 23

Centre - face, arms, torso, legs