2.21 Motor System 3

Question 1

What may disorders of the motor system cause?

Answer 1

• paresis and paralysis
• muscle atrophy
• involuntary muscle contractions
• abnormal muscle tone
• abnormal reflexes
• disturbances of movement efficiency and speed
• impaired postural control

Question 2

paresis

Answer 2

partial loss of voluntary contraction

Question 3

paralysis

Answer 3

complete loss of voluntary contraction

Question 4

types of muscle atrophy

Answer 4

• disuse atrophy
• neurogenic atrophy
• denervation of skeletal muscle

Question 5

disuse atrophy is the result of

Answer 5

lack of muscle use

Question 6

neurogenic atrophy is caused by

Answer 6

damage to nervous system

Question 7

What produces the most severe atrophy?

Answer 7

denervation of skeletal muscle

Question 8

What is essential for the health of skeletal muscle?

Answer 8

frequent neural stimulation, even at a level inadequate to produce muscle contraction

Question 9

spontaneous involuntary contractions include

Answer 9

• muscle spasms
• cramps
• fasciculations
• myoclonus
• tremors
• fibrillations
• abnormal movements generated by dysfunctional basal ganglia

Question 10

hypotonia

Answer 10

abnormally low resistance to passive stretch

Question 11

two types of hypotonia

Answer 11

• velocity-dependent

- velocity-independent

Question 12

velocity-dependent hypotonia

Answer 12

amount of resistance to passive movement depends on velocity of the movement

Question 13

velocity-independent hypotonia

Answer 13

resistance to passive movement remains constant, regardless of speed of force application

Question 14

flaccidity

Answer 14

lack of resistance to passive stretch

Question 15

What can damage LMNs?

Answer 15

• trauma
• infection
• degenerative disorders
• vascular disorders
• tumors

Question 16

if LMN cell bodies and/or axons are destroyed, then affected muscles can undergo:

Answer 16

• loss of reflexes
• atrophy
• flaccid paralysis
• fibrillations

Question 17

UMN lesions can produce several changes in movement control, including:

Answer 17

• paresis or paralysis
• loss of fractionation of movement
• abnormal cutaneous reflexes
• velocity dependent hypertonia

Question 18

paralysis in UMN syndrome

Answer 18

occurs in muscles innervated by LMNs below the level of a complete spinal cord lesion

Question 19

paresis in UMN syndrome

Answer 19

• occurs in UMN lesions as a consequence of inadequate facilitation of LMNs
• common after stroke, in spastic CP, TBI, and incomplete SCI

Question 20

UMN syndrome and loss of fractionation

Answer 20

interferes with fine movements, including fastening buttons or picking up coins, because the fingers of the involved hand act as a single unit

Question 21

UMN syndrome and loss of fractionation: LE

Answer 21

in a lower limb, loss interferes with dorsiflexing the ankle

Question 22

UMN syndrome: abnormal cutaneous reflexes

muscle spasms

Answer 22

• in people with SCI, muscle spasms may occur in response to cutaneous stimuli
• spasms begin after recovery from spinal shock

Question 23

3 most common abnormal reflexes in those with chronic SCIs

Answer 23

• muscle stretch hyperreflexia
• clonus
• clasp-knife response

Question 24

muscle stretch hyperreflexia

Answer 24

• loss of inhibitory corticospinal input combined with LMN and interneuron development of enhanced excitability

Question 25

What does the loss of inhibitory corticospinal input combined with LMN and interneuron development of enhanced excitability result in?

Answer 25

excessive LMN response to afferent input from stretch receptors

Question 26

muscle stretch hyperreflexia: excessive muscle contraction occurs when

Answer 26

when spindles are stretched as a result of excessive LMN firing

Question 27

involuntary, repeating, rhythmic muscle contractions

Answer 27

clonus

Question 28

unsustained clonus

Answer 28

fades after a few beats, even with maintained muscle stretch

Question 29

sustained clonus is always

Answer 29

always pathologic in origin

Question 30

When is sustained clonus produced?

Answer 30

when lack of UMN control allows activation of oscillating neural networks in spinal cord

Question 31

When does clasp-knife response occur?

Answer 31

when paretic muscle is slowly and passively stretched and resistance drops at a specific point in the ROM

Question 32

clasp-knife response: the change in resistance similar to opening of a pocket knife

Answer 32

initial strong resistance to opening gives way to easier movement

Question 33

What afferents elicit the clasp-knife response?

Answer 33

type II

Question 34

problems with velocity dependent hypertonia

Answer 34

• limits joint ROM
• interferes with function
• may cause deformity

Question 35

What is velocity dependent hypertonia caused by?

Answer 35

muscular changes (myoplasticity) and/or spasticity

Question 36

myoplasticity (velocity dependent hypertonia)

Answer 36

adaptive changes within a muscle in response to changes in NM

Question 37

spasticity (velocity dependent hypertonia)

Answer 37

NM overactivity, 2˚ to UMN lesion