motor cortex & descending motor control

Question 1

primary motor cortex location

Answer 1

precentral gyrus of frontal lobe

Question 2

primary motor cortex function

Answer 2

commands the initiation of movements including precise movements

Question 3

primary motor cortex projections

Answer 3

1) directly to alpha motor neurons (lower motor neurons)
2) indirectly to interneurons
3) indirectly to reticular

Question 4

primary motor cortex brodmann’s area

Answer 4

brodmann’s area 4

Question 5

premotor cortex

Answer 5

planning and prepping movements
directing complex motor tasks (production of speech)
expression of emotional behavior

Question 6

reticular motor nuclei

Answer 6

regulating muscle tone

maintaining body posture

Question 7

motor homunculus

Answer 7

• larger areas of motor cortex devoted to body regions with fine/complex movements
• smaller areas to body regions with gross movement/few muscles involved

Question 8

why ‘hand area’ is larger in experienced dentist than the average joe

Answer 8

repetitive motor activity causes the expansion of corresponding motor cortex region

Question 9

cortical metamorphosis

Answer 9

plasticity of the neurons that occupy an area

Question 10

lateral corticospinal tract decussate at

Answer 10

level of medullary pyramids

Question 11

lateral corticospinal tract movements

Answer 11

precise, skilled movements

Question 12

anterior/ventral cortico-spinal tract decussate at

Answer 12

enter spinal cord without crossing midline

Question 13

anterior/ventral cortico-spinal tract movements

Answer 13

posture and balance

Question 14

cortico-spinal tracts are known as

Answer 14

pyramidal tracts

Question 15

pyramidal tracts are formed by…

Answer 15

axons of pyramidal cortical neurons (primary/premotor: 70/30)

Question 16

pathway controlling voluntary movements of the tongue & facial expression

Answer 16

cortico-bulbar pathways

Question 17

voluntary movements of tongue
decussation?
synapse?
innervate?

Answer 17

UMN decussate at level of pyramids (in medulla)
synapse with LMNs
innervate contralateral side of tongue

Question 18

lower motor neurons for tongue muscles

Answer 18

hypoglossal nucleus

Question 19

cortico-bulbar axons of UMN terminate primarily on…..

Answer 19

local circuit neurons (opposed to LMN)

Question 20

majority of cortico-bular inputs to cranial nerve motor nuclei terminate _________
EXCEPTIONS??

Answer 20

• bilaterally

- except: lower face & tongue

Question 21

voluntary movements of facial expression
UMN have bilateral inn. to the LMN where?
upper face innervation?
lower face innervation?

Answer 21

the pons!
upper - bilateral inn.
lower - contralateral inn.

Question 22

lower motor neurons for facial expression muscles

Answer 22

facial nucleus

Question 23

UMN lesion to muscle of upper face

Answer 23

not likely to be affected

because bilateral innervation

Question 24

UMN lesion to muscle of lower face

Answer 24

paralysis of contralateral lower face

Question 25

LMN lesion to muscle of lower face

Answer 25

Bell’s Palsy symptoms to ipsilateral side of face