Upper and Lower Motor Neurons I&II

Question 1

medial to lateral homunculus

Answer 1

lower limbs –> upper limbs –> face –> mouth

• inferior parts of the body –> superomedial cortex
• superior parts of the body –> inferolateral cortex

Question 2

upper and lower motor neuron pathway

Answer 2

upper motor neurons exit via primary motor cortex of cerebral cortex –> corticospinal tract –> synapse with lower motor neurons in spinal cord –> skeletal muscles
-decussate at medullary pyramid

Question 3

betz cells aka giant cells

Answer 3

neurons that run in corticospinal tract to decussate and synapse with lower motor neurons

Question 4

anterior vs. lateral corticospinal tract

Answer 4

• anterior - do NOT decussate; control trunk/axial muscles

- lateral - DECUSSATE; control limbs/digits

Question 5

lower motor neuron innervation

Answer 5

innervate muscle fibers in one muscle –> motor unit

• fine motor control –> few muscle fibers
• gross motor control –> more muscle fibers

Question 6

lower motor neuron arrangements

Answer 6

anterior –> extensors
post/dorsal –> flexors
medial –> proximal muscles
lateral –> distal muscles

Question 7

brodman area 4

Answer 7

primary motor area

Question 8

cerebellum and basal nuclei

Answer 8

affect movement by going through motor areas

-no affect on motor cortex or lower motor neurons with damage, but become uncoordinated

Question 9

vestibulospinal tracts

Answer 9

postural adjustments to body and head

• lateral - antigravity muscles, ipsilateral pathway
• medial - stabilize head, bilateral pathway

Question 10

reticulospinal tract

Answer 10

alternative route for voluntary movement, regulate motor neurons and spinal reflex arc, posture, coordination

Question 11

corticobulbar tract

Answer 11

motor to cranial nerves that innervate muscles

Question 12

which muscles have unilateral innervation via the corticobulbar tract?

Answer 12

lower facial muscles - innervated by CN7 motor neurons

Question 13

lower motor neuron damage

Answer 13

strength - decrease 
tone - decrease 
stretch reflex - decrease 
atrophy - severe 
FML - fibrillations, fasciculations

Question 14

upper motor neuron damage

Answer 14

strength - decrease 
tone - increase 
stretch reflex - increase 
atrophy - mild 
conus, pathological conditions (ex. babinski sign, clonus, etc.)

Question 15

upper motor neuron damage

Answer 15

cause - stroke in primary or premotor cortex

• contralateral flaccid paralysis –> contralateral hypertonicity
• affects upper limb more than lower
• clasp knife affect
• combination of hypertonia and hyperreflexia

Question 16

motor cortex lesions

Answer 16

damage produces CONTRALATERAL motor deficits due to medulla pyramid decussation

Question 17

corticospinal tract lesions

Answer 17

unilateral motor cortex damage –> contralateral deficit for limbs, digits, trunk
unilateral damage below pyramidal decussation –> ipsilateral motor deficit for limbs, digits but contralateral deficit for trunk

Question 18

Bell’s palsy

Answer 18

• lower motor neuron disorder
• hypotonicity, loss of muscle strength, asymmetrical face sagging
• one eye blood shot, the other not

Question 19

hereditary spastic paraplegia

Answer 19

• affect UMN
• progressive gait disorder - weakness and spasticity of lower limb
• looks like CP

Question 20

primary lateral sclerosis (ALS)

Answer 20

• affect UMN

- degenerate motor cortex neuronal cell bodies (Betz cells)

Question 21

amyotrophic lateral sclerosis (Lou Gehrig)

Answer 21

• affect upper and lower motor neurons

- could be limbs or face muscle 1st

Question 22

progressive muscular atrophy

Answer 22

• affect LMN
• usually effects only one limb
• diagnosed with nerve velocity conduction test

Question 23

poliomyelitis

Answer 23

• affect UMN and LMN

- acute viral infection –> rapid paralysis, muscle wasting, respiratory muscles

Question 24

myasthenia gravis

Answer 24

autoimmune disease –> ACh receptors

-neuromuscular junctions disorder

Question 25

benign fasciculation syndrome

Answer 25

infrequent fasciculations affecting random muscles