lecture 29 - motor systems: cerebrum

Question 1

where does the lateral corticospinal tract decussate?

Answer 1

at the level of the caudal medulla

Question 2

where does the lateral corticospinal tract project?

Answer 2

to the limb muscles

Question 3

how does the lateral corticospinal tract project?

Answer 3

contralateral

Question 4

where does the ventral corticospinal tract project?

Answer 4

to the axial muscles

Question 5

how does the ventral corticospinal tract project?

Answer 5

bilateral

Question 6

where does the corticobulbar tract project?

Answer 6

to cranial nerve (V, VII, IX, X, XI, XII) nuclei

Question 7

how does the corticobulbar tract project?

Answer 7

• bilateral: upper face (more common)

- contralateral: lower face (stronger)

Question 8

list the 6 motor and somatosensory cortical areas

Answer 8

• prefrontal cortex
• premotor cortex
• supplementary motor cortex
• primary motor cortex
• somatosensory cortex
• parietal association cortex

Question 9

list the posterior parietal cortical areas

Answer 9

• somatosensory cortex

- parietal association cortex

Question 10

what are the functions of posterior parietal cortical areas?

Answer 10

multi-sensory integration and motor planning

Question 11

what are the functions of supplementary motor areas

Answer 11

• mental rehearsal
• motor imagery
• motor sequences

Question 12

simple finger flexion involves which brain areas?

Answer 12

primary motor cortex, somatosensory cortex

Question 13

sequential finger movements involve which brain areas?

Answer 13

supplementary motor cortex

Question 14

is the supplementary motor cortex unimanual or bimanual?

Answer 14

bimanual

Question 15

what are the functions of the premotor cortex?

Answer 15

• selection of action
• sensory to motor associations - e.g. greenlight/proceed, redlight/stop
• observation of action

Question 16

what are the functions of the prefrontal cortex with respect to movement?

Answer 16

executive functions (highly dextrous movements)

Question 17

which brain area provides the largest contribution to the corticospinal tract?

Answer 17

primary motor cortex

Question 18

does the primary motor cortex contain Betz cells?

Answer 18

yes - aka large corticospinal cells

Question 19

where do corticoneurons synapse

Answer 19

directly onto motoneurons

Question 20

what are corticoneurons innervating?

Answer 20

mainly distal limb musculature

Question 21

motor humunculi are:

Answer 21

somatotopically organized - i.e., have large face and hand representations

Question 22

describe how the primary motor cortex projects

Answer 22

contralateral

Question 23

describe the lateral corticospinal tract’s path

Answer 23

cortex –> corona radiata –> internal capsule –> basis pedunculi (midbrain) –> pyramidal tract –> pyramidal decussation –> sc

Question 24

describe the ventral corticospinal tract’s path

Answer 24

cortex –> corona radiata –> internal capsule –> basis pedunculi (midbrain) –> pyramidal tract –> sc

Question 25

describe the corticospinal tract at the level of the internal capsule in more detail

Answer 25

• located in the posterior limb

- from anterior to posterior: face (genu), arm, trunk, leg

Question 26

describe the corticospinal tract at the level of the midbrain in more detail

Answer 26

• located in the basis pedunculi (base of midbrain)

- from anterior to posterior: face, arm, trunk, leg

Question 27

describe the corticospinal tract at the level of the sc in more detail

Answer 27

• trunk located in ventral corticospinal tract just beside the anterior fissure
• arm, trunk, leg located in the lateral corticospinal tract

Question 28

describe the difference between a corticobulbar lesion and Bell’s Palsy

Answer 28

• corticobulbar: upper motor neuron type facial weakness

- BP: lower-motor neuron type facial weakness

Question 29

describe the direction and target of corticobulbar projections to CN XI

Answer 29

ipsilateral, sternomastoid

Question 30

describe the direction and target of corticobulbar projections to CN XII

Answer 30

bilateral, tongue muscles

Question 31

describe the direction and target of corticobulbar projections to CN IX

Answer 31

bilateral, muscles for swallowing and vocalizing

Question 32

describe the direction and target of corticobulbar projections to CN X

Answer 32

bilateral, muscles for swallowing and vocalizing

Question 33

describe the direction and target of corticobulbar projections to CN VII

Answer 33

bilateral (upper), contralateral (lower), muscles of facial expression

Question 34

describe the direction and target of corticobulbar projections to CN V

Answer 34

bilateral, temporalis, masseter, lateral pterygoid, medial pterygoid

Question 35

is weakness a sign for upper motor neuron lesions? lower motor neuron lesions?

Answer 35

yes both

Question 36

is atrophy a sign for upper motor neuron lesions? lower motor neuron lesions?

Answer 36

lower only (but mild atrophy may develop in upper due to disuse)

Question 37

are fasciculations a sign for upper motor neuron lesions? lower motor neuron lesions?

Answer 37

lower only

Question 38

describe reflexes as a sign for upper motor neuron lesions and lower motor neuron lesions

Answer 38

upper = increased (with acute lesions may decreased)
lower = decreased

Question 39

describe tone as a sign for upper motor neuron lesions and lower motor neuron lesions

Answer 39

upper = increased (with acute lesions may decreased)
lower = decreased

Question 40

describe Babinski reflex test

Answer 40

tickle bottom on foot at heal:

• toes down means the corticospinal tract comes down (good)
• toes up = babinski sign - upper motor neuron lesion (not good)