Upper motor control - Part II

Question 1

Where is the lesion for decorticate posturing?

Answer 1

above red nucleus (superior colliculus and midbrain)

• FLEXED (ELBOWS) PATTERN

Question 2

Where is the lesion for decerebrate posturing?

Answer 2

Below the red nucleus (midbrain, at level of cerebral peduncle)

• EXTENSOR PATTERN
• MORE “E’s”

Question 3

What body parts have poor fine motor control recovery due to their less concentrated representation on M1?

Answer 3

toes, fingers, and tongue

Question 4

How many symmetric concentric topographic representations are there on M1?

Answer 4

3

Question 5

____ is still strictly represented in homunculus

Answer 5

S1

Question 6

There is a chimeric distribution of ___

Answer 6

M1

• mixture of columnar units

Question 7

What are the functions of M1 in motor control?

Answer 7

• 1st stimulated, faster response, these UMN can directly control our LMN in the spinal cord

Question 8

What is the delay of M1?

Answer 8

5-100 msec delay

• PM is 1/2 second due to more pathways, each step takes time

Question 9

What kind of synapse is formed with LMN from M1?

Answer 9

direct monosynaptic LMN control

• directly form a synapse with LMN without interneurons
• if interneurons are needed (2+) = disynaptic

Question 10

What are the roles of M1 for motor control?

Answer 10

• the intention/direction of the movement
• the preferred direction of movement
• the force/speed of movement
• the extent of movement: proprioception mediated

Question 11

Where is the strongest activity of M1?

Answer 11

like 360 degrees, 4 oclock to 8 oclock is strongest activity that a motor neuron works

Question 12

Which cerebral lobe doesn’t have mirror neurons?

Answer 12

Occipital lobe, mainly for visual stimuli

Question 13

When are monosynaptic M1 neurons developed?

Answer 13

postnatally

Question 14

Where are monosynaptic neurons located?

Answer 14

caudal M1, anterior bank of central sulcus

Question 15

What do monosynaptic M1 neurons directly synapse with? Why?

Answer 15

LMN: fine motor control

Question 16

Why do reflexes reappear stroke?

Answer 16

• integrated, disappear as time goes on after we are born, maturation of system caudal M1 axons descend to the spinal cord, will inhibit these reflexes
• why after stroke, with functions lost, pts will present with spinal reflexes again, such as Babinski and Hoffman

Question 17

When are level 3 and 4 disynaptic UMNs developed?

Answer 17

prenatally

Question 18

How do levels 3 and 4 disynaptic UMNs synaps with LMN? Where?

Answer 18

through interneurons

• rostral M1
• Dorsal and vental PM, SMA: Brodmann area 6
• two from cingulate gyrus: RCZ, CCZ
• posterior parietal lobe: Brodmann area 5

Question 19

What tracts do levels 3 and 4 UMNs not contribute much to?

Answer 19

human corticcobulbar and corticospinal tracts

Question 20

What is unique about cortical descending projection fibers?

Answer 20

ROTATE DURING DESCENDING 180 degree until to pons
- at the posterior limb of the internal capsule

Question 21

What happens with cortical descending projection fibers below the pons?

Answer 21

disperse out, mix together
- NO MORE SOMATOTOPY

Question 22

What is maintained with cortical descending projection fibers above the pons?

Answer 22

gross topography maintained above the pons

Question 23

What are the cortical desscending projection fibers?

Answer 23

• corticobulbar
• corticospinal

Question 24

Where are 2/3 of the tracts in the internal capsule from?

Answer 24

frontal lobe

Question 25

Where are the target motor nuclei for the corticobulbar tracts?

Answer 25

in the brainsetm

Question 26

What cranial nerves DO NOT have motor nuclei?

Answer 26

III, IV, VI

Question 27

Which CN is the only one entirely by contralateral control?

Answer 27

CN XII

Question 28

What can happen with a R MCA stroke?

Answer 28

L CN XII compromised, tongue shifts L with tongue protrusions - tongue will deviate to weaker side

Question 29

What CN have contralateral control?

Answer 29

CN VII ventral nuclei, CN XII

Question 30

Which CN have bilateral control?

Answer 30

All other CNs

Question 31

What level has brainstem motor control functions for the corticobulbar tract?

Answer 31

Level 2

Question 32

What is in the brainstem motor control level 2 of corticobulbar tracts?

Answer 32

red/reticular/vestibular nuclei - inhibition vs activation

Question 33

What percentage of the corticospinal tracts decussate in the pyramid?

Answer 33

70-90% for contralateral body control

Question 34

Where do the corticospinal tracts that decussate in the pyramid descend?

Answer 34

in the lateral funiculus

Question 35

Where do the corticospinal tracts that do not cross over descend?

Answer 35

anterior funiculus and ipsilateral lateral funiculus

Question 36

Why do patients who have the nondecussated tracts stroke recover better?

Answer 36

- more function and fine motor control

Question 37

Where does motor decussation occur?

Answer 37

in the caudal medulla

Question 38

What are the 3 tracts in the pons ?

Answer 38

- pontine reticulospinal tract - vestibulospinal tract (lateral and medial)

Question 39

What is the tract in the medulla?

Answer 39

medullary reticulospinalt ract

Question 40

What tract is in the midbrain?

Answer 40

rubrospinal tract

Question 41

What are the functions of the monosynaptic M1 neurons?

Answer 41

directly innervate LMN - direction speed and extension of a selected movement

Question 42

What are the functions of the red nucleus for UE fine motor control?

Answer 42

Flexors - decussation in midbrain - descending in the lateral funiculus of the spinal cord

Question 43

Where does the UE fine motor control of the red nucleus end?

Answer 43

Upper thoracic region

Question 44

What is the red nucleus important for?

Answer 44

New Skill Learning - through red nucleus- inferior olivary nucleus - cerebellum circuitry

Question 45

Where does the pontine reticulospinal tract run? What does it control?

Answer 45

- all spinal levels - controls extensors

Question 46

Where does the pontine reticulospinal tract project?

Answer 46

bilateral projection, anterior funiculus

Question 47

Where does the medullary reticulospinal tract run? What does it control?

Answer 47

all spinal levels/whole spinal cord - controls flexors

Question 48

Where does the medullary reticulospinal tract project?

Answer 48

ipsilateral projection, lateral funiculus

Question 49

Where does the lateral vestibulospinal tract run? What is its function?

Answer 49

- ipsilateral anterior funiculus for proximal extremity extensors - WHOLE SPINAL CORD

Question 50

Where does the medial vestibulospinal tract run? What is its function?

Answer 50

- Ends at upper level of thoracic region - bilateral anterior funiculus for neck/upper trunk extensors

Question 51

What motor control reflexes help with balance?

Answer 51

- vestibulocular reflex - vestibulocervical reflex - vestibulospinal reflex

Question 52

What tracts that control extensors run the whole spinal cord?

Answer 52

- Pontine reticulospinal tract (pRST) - lateral vestibulospinal tract (lVST)

Question 53

What extensor tract ends in the neck?

Answer 53

medial vestibulospinal tract (mVST)

Question 54

What flexor tract ends in the UE?

Answer 54

Rubrospinal tract (RuST)

Question 55

What flexor tract runs the whole spinal cord?

Answer 55

Medullary reticulospinal tract (mRST)

Question 56

What pathology is BELOW the red nucleus?

Answer 56

decerebrate

Question 57

What is unique about decerebrate posturing?

Answer 57

NO corticospinal/rubrospinal functions - extremities in EXT

Question 58

What pathology is above the red nucleus?

Answer 58

Decorticate

Question 59

What are the tracts responsible for decorticate posturing?

Answer 59

- Functional rubrospinal tract: UE in FLX - Active vestibulospinal tracts: BLE in extension

Question 60

Which level 2 motor contro systems in the brainstem?

Answer 60

- Rubrospinal tract (midbrain) - reticular: pontine vs medullary (pons) - Vestibular: lateral vs medial (pons)

Question 61

Which level 2 motor control tracts end in the whole spinal cord, and which stop at the upper thoracic region?

Answer 61

- Whole spinal cord: pontine and medullary reticulospinal tracts, lateral vestibulospinal tract - Upper thoracic region: rubrospinal tract and medial vestibulospinal tract

Question 62

What controls reflexes?

Answer 62

Caudal M1