Control Lecture 6: Descending motor pathways

Question 1

Causes of lower motor neuron lesions?

Answer 1

Traumatic injury

Poliomyelitis

Question 2

Symptoms of lower motor neuron lesions?

Answer 2

Muscle wastage
Muscle weakness
Hypotonia
Absent reflexes
Fasciculation/fibrillation

Question 3

Functions of upper motor neurons?

Answer 3

Modify LMN activity
Modify reflexes
Coordinate complex movements

Question 4

Where is the primary motor cortex in the brain?

Answer 4

Precentral gyrus

Question 5

Initial symptoms of upper motor neuron lesions?

Answer 5

Paralysis of opposite limbs

Loss of reflexes

Question 6

Symptoms of upper motor neuron lesions after a few weeks?

Answer 6

Reduced but partially recovered function

Hypertonia

Question 7

Symptoms of upper motor neuron lesions in the long term?

Answer 7

Hyperreflexia

Spasticity

Question 8

How is the precentral gyrus somatotopically organised from medial to lateral?

Answer 8

Legs
Trunk
Arms
Face
Tongue
Throat

Question 9

What is the function of the corticospinal tract?

Answer 9

Fine motor movements

Question 10

Where does the corticospinal tract pass to from the precentral gyrus?

Answer 10

Internal capsule

Question 11

Where in the internal capsule do descending fibres to the face pass through?

Answer 11

Genu

Question 12

Where in the internal capsule do descending fibres to the body pass through?

Answer 12

Posterior limb

Question 13

How is the posterior limb of the internal capsule somatotopically organised from anterior to posterior?

Answer 13

Arms
Trunk
Legs

Question 14

Does the corticospinal tract pass along the ventral or dorsal side of the brainstem?

Answer 14

Ventral

Question 15

What structures in the midbrain does the corticospinal tract pass through?

Answer 15

Cerebral peduncles

Question 16

What structures in the medulla does the corticospinal tract pass through?

Answer 16

Pyramids

Question 17

Where is the decussation of the corticospinal tract?

Answer 17

Pyraminds of the medulla

Question 18

How is the corticospinal cord in the brainstem organised from lateral to medial?

Answer 18

Legs
Trunk
Arms
Face

Question 19

Roughly what percentage of fibres in the corticospinal tract cross in the main decussation?

Answer 19

85%

Question 20

Where do fibres travel in after the decussation in the pyramids?

Answer 20

Lateral corticospinal tract

Question 21

Where do fibres that don’t decussate in the pyramids descend in the spinal cord?

Answer 21

Ventral corticospinal tract

Question 22

Where do fibres in the corticospinal tracts enter the ventral grey horn?

Answer 22

At the spinal cord level where their rootlets exit

Question 23

Is the ventral corticospinal tract contralateral or ipsilateral to the origins of the fibres in the brain?

Answer 23

Ipsilateral

Question 24

Within what do fibres in the ventral corticospinal tract decussate?

Answer 24

Ventral white commissure

Question 25

How is the lateral corticospinal tract somatotopically organised from anterior to posterior?

Answer 25

Arm
Trunk
Legs

Question 26

What is the name of the descending motor pathway to the face?

Answer 26

Corticobulbar pathway

Question 27

Which cranial nerves aren’t innervated bilaterally?

Answer 27

Facial (VII)

Hypoglossal (XI)

Question 28

How is the hypoglossal nerve served?

Answer 28

Contralaterally

Question 29

How is the upper face served by the facial nerve?

Answer 29

Bilaterally

Question 30

How is the lower face served by the facial nerve?

Answer 30

Contralaterally

Question 31

Would paralysis across half of the face characterise lower or upper motor neuron damage?

Answer 31

Lower

Question 32

Would paralysis across a quarter of the face characterise lower or upper motor neuron damage?

Answer 32

Upper