Lower Motor Neurons

Front 1

What are the four motor systems?

Back 1

1) Higher centers
2) Brainstem
3) Spinal Cord
4) Motor unit

Front 2

What is the function of the motor unit in terms of motor activity?

Back 2

muscle contraction

Front 3

What is the function of the spinal cord in terms of motor activity?

Back 3

spinal reflexes

Front 4

What is the function of the brainstem in terms of motor activity?

Back 4

control of posture

Front 5

What is the function of the higher centers in terms of motor activity?

Back 5

voluntary movement planning and execution

Front 6

What structures are considered part of the upper motor neurons? (4)

Back 6

1)motor cortex
2)basal ganglia
3)cerebellum
4)brainstem

Front 7

What structures are considered part of the lower motor neurons?

Back 7

1) spinal reflexes
2) motor neurons

Front 8

What structures are the common final pathway?

Back 8

motor unit

Front 9

In the spinal cord what is the topigraphical distribution for the proximal/axial muscles?

Back 9

medial

Front 10

In the spinal cord what is the topigraphical distribution for the distal/extremity muscles?

Back 10

lateral

Front 11

In the spinal cord what is the topographical distribution of the flexor muscles?

Back 11

dorsal

Front 12

In the spinal cord what is the topographical distribution of the extensor muscles?

Back 12

ventral

Front 13

What are the components of the motor unit?

Back 13

1) single motor neuron
2) motor neuron axon fibers
3) muscle fibers that the motor neuron innervates

Front 14

hat is the motor neuron pool?

Back 14

group of motor neurons that innervate muscle fibers within th same muscle

Front 15

What is the innervation ratio?

Back 15

muscle fibers per neuron

Front 16

Which muscles have the highest innervation ratio?

Back 16

large motor neurons

Front 17

Which muscles have the lowest innervation ratio?

Back 17

small motor neurons

Front 18

What are the three different types of motor units?

Back 18

1) slow motor units
2) fast fatigue resistant motor units
3) fast fatigable motor units

Front 19

What is the size principle of recruitment order?

Back 19

1) slow motor units
2) fast fatigue resistant motor units
3) fast fatigable motor units

Front 20

Are smaller or larger motor units more likely to fire first or last?

Back 20

small motor units are more likely to fire first

Front 21

Which of the motor unit sizes has a lower threshold smaller or bigger motor units?

Back 21

smaller

Front 22

Which of the motor units generates the most amount of force, smaller or larger?

Back 22

larger

Front 23

What type of neuron is associated with an intrafusal muscle fiber/spindle?

Back 23

alpha motor neuron

Front 24

What type of neuron is associated with a nuclear chain fiber?

Back 24

gamma motor neuron

Front 25

What type of interfusal fiber neuron is associated with a dynamic response?

Back 25

group 1a

Front 26

What type of interfusal neuron is associated with a static response?

Back 26

group ii

Front 27

What is the muscle stretch reflex?

Back 27

1) stretch on muscle spindle
2) Ia afferents bring in the signal in the spinal cord
3) alpha motor neurons act on muscle

Front 28

What is recipical innervation?

Back 28

antagonist muscle is inhibited by an interneuron

Front 29

is the stretch reflex monosynaptic?

Back 29

yes

Front 30

What is the effect of stretch or contraction on the Ia afferents?

Back 30

stretch - activates them
contraction - inhibits them so you will stop contracting

Front 31

What is the Jendrassik manuever?

Back 31

you increase gamma stimulation to the muscle this increases sensitivity of muscle spindle at different lengths

Front 32

What is the role of gamma motor neurons?

Back 32

you get a sensitivity of muscle at different lengths like even while you are contracted

Front 33

What is the principle of coactivation?

Back 33

Alpha motor neuron stimulation causes gamma motor neuron costimulation which allows muscle spindles to maintain sensitivity during muscle contraction

Front 34

What is the best activator of the golgi tendon orgal?

Back 34

active contraction of extrafusal muscle fibers

Front 35

What is the different intrafusal vs extrafusal for which type of sensory receptor in muscle? what about type of motor neuron fiber?

Back 35

intrafusal - nuclear chain and bag/muscle spindle (gamma)
extrafusal - golgi tendon organ (alpha)

Front 36

Does the golgi tendon organ respond well to passive stretch? What does?

Back 36

no, the extrafusal/golgi tendon organ does not respond. it responds best to active contraction. well but the intrafusal/spindle afferent does

Front 37

Does the muscle spindle respond well to active stretch? what does?

Back 37

intrafusal organ responds well to passive stretch

Front 38

What is the Golgi Tendon/inverse motatic reflex?

Back 38

1) Golgi tendon organ senses force
2) Ib afferents relay that force to spinal cord
3) inhibition of homonymous (same muscle fiber) by interneurons
4) activation of antagonists by interneurons

Front 39

Is the golgi tendon/inverse myotatic or the myotactic disynaptic? Which one is monosynaptic which one is disynaptic?

Back 39

golgi tendon - disynpatic
muscle spindle - monosynaptic

Front 40

Which sensory fibers are associated with the Golgi tendon organ?

Back 40

1b

Front 41

What stimuli is the flexor withdrawal reflex associated with?

Back 41

touch, temperature, pain

Front 42

What is the flexor withdrawal reflex?

Back 42

1) touch, temperature and pain afferents go to interneurons in spinal cord
2) ipsilateral flexion is activated
3) ipsilateral extension is inhibited

Front 43

What is crossed extension in the flexor-withdrawal reflex?

Back 43

contralateral extension is activated
contralateral flexion is inhibited

Front 44

What is the after discharge in the flexor withdrawal reflex?

Back 44

residual ipsilateral extensor inhibition and flexor activation so you are in that position for a bit longer

Front 45

What are the sensory fibers that do the afferents of the flexor withdrawl reflex?

Back 45

1)group II
2) group III (a delta)
3) group IV/C fibers

Front 46

What is the purpose of the crossed extension?

Back 46

ipsilateral flexion/withdrawal and contralateral extension to help you maintain balance

Front 47

What is the stimulus/sensory organ, afferent, synapse and response for the stretch reflex?

Back 47

Stimulus- Muscle Spindle
Afferent - Ia
Synapse - One/Monosynaptic
Response- Contraction

Front 48

What is the stimulus/sensory organ, afferent synapse and response for the golgi tendon reflex?

Back 48

Stimulus- Golgi tendon
afferent - Ib
Synapses- Disynaptic
Response - Relaxation

Front 49

What is the stimulus/sensory organ, afferent synapse and response for the flexor withdrawal reflex?

Back 49

stimulus - touch, temperature and pain
afferent - II, III, IV
synapse - polysynaptic
response - ipsilateral flexion

Front 50

What is lower motor neuron syndrome?

Back 50

1)paralysis/loss of movement or weakness (paresis)
2) loss of reflexes
3) loss of muscle tone
4) muscle atrophy
5) fasiculations (spontaenous muscle twitches)

Front 51

What is the cause of Amyotrophic lateral sclerosis (ALS)?

Back 51

1)slow degeneration of motor neurons in spinal cord (LMNs) and motor cortex (UMNs)

Front 52

What are the symptoms of ALS?

Back 52

1) progressive weakness, atrophy and muscle twitching
2) sensory function is unaffected 3)mental status/intellect remains intact