Motor Control

Question 1

what type of motor neurons have direct control of muscles in the spinal cord ?

Answer 1

alpha motoneurones

Question 2

what are the four systems which provide information for movement?

Answer 2

basal ganglia
cerebellum
local spinal cord
brain stem circuits

Question 3

what would be the result of a lower motor neuron lesion?

Answer 3

flaccid paralysis and muscle atrophy

Question 4

what would be the result of a upper motor neuron lesion?

Answer 4

spasticity
rigidity

• as the reflex arcs aren’t affected so the involuntary reflexes would still occur
• there are many synapses, including inhibitory synapses so rigidity is possible

Question 5

what does corticospinal lesions result in?

Answer 5

weakness

- rather than paralysis

Question 6

what muscles correlate with the medial motor neurons ?

Answer 6

shoulder muscles

Question 7

what muscles correlate with the lateral motor neurons ?

Answer 7

finger muscles

Question 8

is sensory input required for motor neurons to function properly?

Answer 8

yes

Question 9

what is another name for the corticospinal tract?

Answer 9

pyramidal tract

Question 10

what sensory information does the brain stem receive?

Answer 10

information about balance form the vestibular system

Question 11

what sensory information does the cortex receive ?

Answer 11

visual 
auditory 
emotional 
smell 
intellectual cues

Question 12

what sensory information does the spinal cord receive ?

Answer 12

touch
pain
proprioceptors

Question 13

what are the three levels of hierarchy for motor control?

Answer 13

cortex
brain stem
spinal cord

Question 14

how does the spinal cord receive information from descending tracts?

Answer 14

from direct cortical input via the brain stem where tracts travel through the pyramidal tract

Question 15

what does DRG stand for?

Answer 15

dorsal root ganglia

Question 16

what would be the result if a patient lost all their proprioception?

Answer 16

loose the sense of where your body was in space and motor control

Question 17

what would cause a patient to loss their proprioception?

Answer 17

lose of sensory neurons in the dorsal root ganglia

Question 18

how do reflexes help to determine where the problem/damage is?

Answer 18

reflexes are related to certain cord segments so-

if one reflex is present but another one is absent then you can determine what level the problem is present at

Question 19

what are nociceptors ?

Answer 19

pain receptors

Question 20

what is the pain reflex called?

Answer 20

flexor reflex

Question 21

are nociceptive fibres confined to a single spinal level?

Answer 21

no

Question 22

which neurons do nociceptive fibres activate?

Answer 22

alpha motor neurons

Question 23

flexor reflex

- as well as contracted and relaxing ipsilateral muscles, what other mechanisms are done?

Answer 23

excitatory interneurones cross the spinal cord and excite the contralateral extensors

inhibitory interneurones also cross over and there is inhibition of the contralateral flexors

Question 24

flexor reflex

- as well as changing the muscles on the ipsilateral side, why are the muscles affected on the contralateral side ?

Answer 24

to maintain balance and posture

Question 25

where does sensory information ascend to from the spinal cord?

Answer 25

contralateral spinothalamic tract to the thalamus

Question 26

what is the flexor reflex called when the contralateral side is also involved ?

Answer 26

flexor-crossed extensor reflex

Question 27

which reflex is faster ?

• stretch reflex
• flexor crossed extensor reflex

Answer 27

stretch reflex

• less synapses
• muscle spindles have thicker diameter than nociceptors

Question 28

what is the golgi body reflex?

Answer 28

when there is a stretch on the muscle, the golgi tend bodies are stretched and cause the motor neurons to relax and the muscle relaxes
- this prevents the muscle from ripping

Question 29

can reflexes be over ridden ? (such as golgi tendon reflex of relaxing your arm)

Answer 29

yes

descending voluntary excitation of motoneurones can override the inhibition from the GTOs and maintain contraction.

Question 30

what reflex is occurring when holding something heavy in your hands with your elbow at 90 degrees?

Answer 30

stretch reflex

Question 31

does one alpha motor neuron synapse with one other neuron ?

Answer 31

no

- more than 10,000 synapses mostly from cortical excitatory or inhibitory inputs (sensory inputs)

Question 32

what pathways do gamma motor neurons depend on?

Answer 32

activity of gamma-motoneurones depends entirely on descending pathways

Question 33

what is the difference between the alpha and gamma motor neurons ?

Answer 33

alpha motor neurons = innervate extrafusal muscle fibres

gamma motor neurons = innervate intrafusal muscle fibres

Question 34

if the pain area is large enough can the pain fibres spread through several spinal levels?

Answer 34

yes

Question 35

what is facilitation of sensory input?

Answer 35

the enhancement of the response of a neuron to a stimulus following prior stimulation
- for example, finger on hot plate will result in hand being pulled away but may also cause the contralateral arm to extend as well

Question 36

what is the sign when their is plantar extension instead of flexion?

Answer 36

babinski sign

Question 37

what is spinal shock?

Answer 37

combination of hyporeflexia (lose of reflexes) and autonomic dysfunction that accompanies spinal cord injury.
- the reflexes gradually start to come back as other pathways are formed

Question 38

what is clonus ?

Answer 38

stretch causes oscillatory muscle contraction/relaxation