9. Motor Systems

Question 1

do you need the cortex for movement?

Answer 1

no (remember your decerebrated cat experiment)

Question 2

assemblies of neurons that produce rhythmic patterns of neural activity without rhythmic inputs

Answer 2

central pattern generators (CPGs)

Question 3

where are central pattern generators (CPGs) found?

Answer 3

found in the spinal cord

Question 4

when the flexors are active, the extensors are:

Answer 4

silent (and vice versa)

Question 5

• found in the frontal lobe
• responsible for executing voluntary movements
• relays motor signals to the brainstem and spinal cord
• controls the opposite side of the body
  these are all characteristics of:

Answer 5

the motor cortex

Question 6

true or false: there is somatotopic organization in the primary motor cortex (M1)

Answer 6

true

Question 7

prolonged stimulation (0.5s) of M1 areas elicits:

Answer 7

sterotyped, complex movements

Question 8

go review slides 562-563

Answer 8

:P

Question 9

a key component of the somatotopic organization of M1 are the:

Answer 9

action zones

Question 10

true or false: M1 acts alone to to generate motion

Answer 10

false

Question 11

list four areas of the cortex, other than M1, that are involved in motor planning

Answer 11

• supplementary motor cortex (SMA)
• premotor cortex (PMC)
• frontal eye field (FEF)
• posterior parietal motor area (PMA)

Question 12

fire when performaing a task or watching someone else perform the same task

Answer 12

mirror neurons

Question 13

where are mirror neurons found?

Answer 13

• F5 in the ventral PMC cortex (especially F5c)
• the inferior parietal area in the PMA

Question 14

how many descending motor pathways are there? where do they arise from?

Answer 14

at least seven
- three arise from the motor cortex (MI and MII)
- four arise from the brainstem and midbrain nuclei

Question 15

of the motor pathways that arise from the motor cortex, the descending signals originate mainly within:

Answer 15

layer V pyramidal neurons

Question 16

upper motorneurons from the brain synapse onto:

Answer 16

lower motorneurons in the spinal cord

Question 17

what are the three descending motor pathways that arise from the motor cortex (MI and MII)?

Answer 17

• lateral corticospinal tract
• anterior corticospinal tract
• corticonuclear tract

Question 18

what are the four descending motor pathways that arise from the brainstem/midbrain?

Answer 18

• rubrospinal tract
• vestibulospinal tract
• reticulospinal tract
• tectospinal tract

Question 19

the corticospinal tracts arise from:

Answer 19

layer V pyramidal cells

Question 20

neurons from the corticospinal tracts leave the motor cortex as the _____ and descend through the _____

Answer 20

corona radiata, internal capsule

Question 21

where do the corticospinal tracts dessucate (“cross over”)?

Answer 21

the pyramids of the medulla

Question 22

when the corticospinal tracts dessucate, they split into the:

Answer 22

lateral and anterior corticospinal tracts (LCST and ACST)

Question 23

synapses on interneurons and lower motorneurons innervating the distal limb musculature for rapid skilled movements

Answer 23

lateral corticospinal tract (LCST)

Question 24

synapses on interneurons and lower motorneurons innervating the proximal and axial musculature for postural control

Answer 24

anterior corticospinal tract (ACST)

Question 25

a positive Babinski reflex (dorsiflexion of toes) is indicative of:

Answer 25

corticospinal tract damage

Question 26

what type of reaction is 'normal' in a babinski reflex?

Answer 26

negative (curling the toes)

Question 27

the corticonuclear (corticobulbar) tract contains projections from:

Answer 27

M1, PMA, and S1

Question 28

the corticonuclear (corticobulbar) tract descends with the corticospinal tract and splits at the:

Answer 28

brainstem above the pyramidal decussation

Question 29

where does the corticonuclear (corticobulbar) tract terminate?

Answer 29

cranial nerve motor nuclei

Question 30

the corticonuclear tract is mainly associated with control of:

Answer 30

face musculature

Question 31

arises from the red nucleus in the rostral midbrain, decussates in the ventral tegmentum, travels just ventral to the LCST, and terminates in the cervical and thoracic levels (ie: upper limbs)

Answer 31

rubrospinal tract

Question 32

the rubrospinal tract is important for:

Answer 32

arm and hand movements (including fine motor control)

Question 33

the vestibulospinal tract arises from:

Answer 33

the vestibular nuclei

Question 34

the vestibulospinal tract separate into:

Answer 34

medial and lateral vestibulo-spinal tract (MVST and LVST)

Question 35

originates in the medial vestibular nucleus in the cervical spinal cord, and is involved in head control

Answer 35

the MVST

Question 36

originates in the lateral vestibular nucleus and terminates throughout the spinal cord, particularly motorneurons for axial musculature (antigravity muscles of the limbs)

Answer 36

the LVST

Question 37

the reticulospinal tracts have extensive inputs from:

Answer 37

MI and MII

Question 38

what are the two reticulospinal tracts and where do they originate?

Answer 38

- medial RST: originates in the pontine nucleus - lateral RST: originates in the medulla

Question 39

both the medial and lateral reticulospinal tracts are involved in:

Answer 39

posture/balance

Question 40

the medial reticulospinal tract excites ______, and the lateral reticulospinal tract inhibits ______ and controls _______

Answer 40

anti-gravity extensors, anti-gravity extensors, muscles for breathing

Question 41

the tectospinal tract originates in the:

Answer 41

optic tectum

Question 42

has extensive input from the frontal eye fields (FEF) of MII, and projects to the cervical cord subserving the neck muscles

Answer 42

tectospinal tract

Question 43

the tectospinal tract is responsible for:

Answer 43

orienting the head to stimuli of interest

Question 44

go review slide 589

Answer 44

it's... kind of a cool diagram