10d: Cortex IV (Motor Neurons)

Question 1

Brainstem control of motor systems is mediated by (X) tracts. List them.

Answer 1

X = subcorticospinal

1. Rubrospinal
2. Tectospinal
3. Reticulospinal
4. Vestibulospinal

Question 2

Cortical control of subcorticospinal tracts is mediated by (X) pathways. And cortical control of spinal cord is mediated by (Y) pathways.

Answer 2

X = corticobulbar
Y = corticospinal

Question 3

T/F: Subcorticospinal tracts, like corticospinal tract, travel through pyramids.

Answer 3

False - “extra-pyramidal”

Question 4

(Lateral/medial) subcorticospinal pathways descend (ipsilaterally/contralaterally/bilaterally), but always terminate bilaterally on the interneurons. List these pathways.

Answer 4

Medial;
Either ipsilaterally or bilaterally;

1. Tectospinal
2. Medial vestibulospinal
3. Medial reticulospinal

Question 5

The tectospinal tract arises from (X), crosses at (Y), and descends to which SC segments? What’s its function?

Answer 5

X = deep layers of Superior Colliculus
Y = dorsal midbrain (tegmentum)

Coordinate head/neck and eye movements

Question 6

Reticulospinal pathways arise from (X) and descend to which SC segments? They have (excitatory/inhibitory) effect.

Answer 6

X = pontine and medullary reticular formation
Entire length of SC;
Excitatory (pontine) and inhibitory (medullary)

Question 7

Premotor cortex, Brodmann’s area (X), is located immediately rostral to (Y), Brodmann’s area (Z).

Answer 7

X = 6;
Y = primary motor cortex (pre-central gyrus)
Z = 4

Question 8

Movements involving discrete muscle groups, instead of entire limbs, occurs when evoking (primary/pre-) motor cortex.

Answer 8

Primary

Question 9

Where is the supplementary motor cortex?

Answer 9

Subdivision of premotor cortex (medial/dorsal subdivision)

Question 10

Mirror neurons are unique in that (X) causes them to fire. Where are these neurons found?

Answer 10

X = observing an action in others

Lateral premotor cortex

Question 11

Frontal Eye Fields, Brodmann’s area (X), is located immediately rostral to (Y). Stimulation to this area evokes:

Answer 11

X = 8
Y  = premotor cortex (BA 6)

Movement of eyes to contralateral side

Question 12

Damage to Frontal Eye Fields area impairs:

Answer 12

Attention to contralateral visual field

Question 13

Corticobulbar projections from Frontal Eye Fields area connect to (X). Lesions at (X) impair:

Answer 13

X = pontine gaze center (area of reticular formation)

Lateral eye movement to opposite visual field (but no effect on attention)

Question 14

List the sources of cortical afferents to the primary motor cortex.

Answer 14

1. Premotor cortex
2. Somatosensory cortex
3. Contralateral motor cortices

Question 15

List the sources of subcortical afferents to the primary motor cortex.

Answer 15

VA/VL thalamus

Question 16

Corticobulbar projections to CN (X) nuclei are bilateral.

Answer 16

X = 5, 10, 12

Question 17

Corticobulbar projections to CN (X) nuclei are, in part, unilateral, specifically (ipsi/contra)-lateral.

Answer 17

X = 7

Contralateral

Question 18

You notice your patient has slight drooping of R lower lip. When asking him to smile, he’s unable to produce smile on that side. Where’s the damage?

Answer 18

L primary motor cortex (BA 4) in lateral region (area of face)

Question 19

You notice your patient has slight drooping of R lower lip. You discover damage to Area 4. Would he likely smile at a humorous joke you tell him?

Answer 19

Yes

Question 20

The facial nucleus receives (unilateral/bilateral) corticobulbar innervation from which cortices?

Answer 20

1. Unilateral from primary motor cortex

2. Bilateral from cingulate cortex

Question 21

Tectobulbar connections refer to fibers projecting to (X) from (Y).

Answer 21

X = horizontal and vertical gaze centers (in midbrain reticular formation)
Y = deep tectal nuclei (SC/IC)

Question 22

T/F: In humans, unlike other mammals, the lateral vestibulospinal tract is largely restricted to control of lower limb extensors.

Answer 22

True

Question 23

T/F: After bilateral corticospinal tract interruption, wide range of normal motor activity is largely lost in animal studies.

Answer 23

False - subcorticospinal pathways sufficient to guide wide range of these activities

Question 24

The Pyramidal Syndrome is a result of damage to (X). This impairs (upper/lower) motor neurons. What are the signs of this syndrome?

Answer 24

X = either motor cortices or fibers in internal capsule
UPM

1. Paralysis/paresis
2. Hyper-reflexia
3. Spasticity
4. Babinski’s sign

Question 25

Babinski’s sign is:

Answer 25

Dorsiflexion/extension of great toe when stroking lateral border of foot

Question 26

Lesion that produces pyramidal tract signs may initially present with (spastic/flaccid) paralysis, which then gradually evolves into (spastic/flaccid) paralysis.

Answer 26

Flaccid; spastic

Question 27

Lesions restricted to motor cortex produce paralysis mainly of (X) musculature. Which symptoms may be missing from this lesion, compared to pyramidal tract syndrome?

Answer 27

X = distal;

Babinski sign, spasticity, and/or hyper-reflexia

Question 28

List the only signs that can be strictly called pyramidal/corticospinal.

Answer 28

1. Sign of Babinski

2. Impairment of movement to most distal extremities

Question 29

Target-related AP: neurons that fire maximally in response to specific direction of movement are found in which motor cortex?

Answer 29

Primary motor cortex

Question 30

Neurons in (X) cortex fire AP in response to cue that indicates an action will be undertaken (ex: monkey sees red light and knows blue light to press button is coming).

Answer 30

X = ventral premotor (BA 6)

Question 31

You’re about to do a bicep curl. Feedforward via (X) tract(s) regulate postural instability by (activating/inhibiting) gastrocnemius.

Answer 31

X = corticospinal and corticobulbar;

Activating

Question 32

You’re about to do a bicep curl, but you begin to tilt back due to unanticipated postural instability. You don’t fall due to feedback from (X) tracts/structures for postural adjustment.

Answer 32

X = vestibulospinal, reticulospinal, and cerebellar

Question 33

You’re about to do a bicep curl, so your gastrocnemius is involved to maintain posture. Will the biceps or the gastrocnemius EMG spike first?

Answer 33

Gastrocnemius EMG