Motor Control

Question 1

What is fibrillation

Answer 1

undetectable, unexpected movements of muscle sub-divisions

Question 2

What is scanning speech caused by?

Answer 2

cerebellum lesion

Question 3

Why does the NMJ have a “secure synapse”

Answer 3

because of the spread out synaptic cleft with plenty of embedded Nic receptors, an impulse is guaranteed to cause a contraction

Question 4

Which muscles are recruited first when straining?

Answer 4

the smaller muscle units are recruited first. These units are slow twisting and resistant to fatigue

Question 5

T/F Muscle strength grows in increments

Answer 5

True, neurotransmitters are released in discrete units. The more neural signal = more muscular contraction

Question 6

T/F each muscle is made up of a number of identical motor units

Answer 6

False, muscle is made of motor units of varying sizes so there is a fine control of the force applied

Question 7

With 50% of motor neuron recruitment, how much force can be generated?

Answer 7

25% of max force

Question 8

What are the short term consequences of denervation on lower motor neurons?

Answer 8

fibrillation and fasciculation

Question 9

What is fasciculation?

Answer 9

measurable, spontaneous twitching of muscle fibre

Question 10

Why do muscles fibrillate?

Answer 10

Where there is denervation, the initial compensation is to increase sensitivity to Ach, which means increased Ach receptors and moving receptors outside the junction. Therefore, muscles are more likely to be activated spontaneously in very small magnitude

Question 11

What is the long term consequence of denervation?

Answer 11

atrophy and degeneration (irreversible

Question 12

T/F muscles are inactive if not used

Answer 12

False, all muscles have a resting tone, allowing anticipation of contraction

Question 13

Which part of the brain regulates muscle tone?

Answer 13

cerebellum

Question 14

The UMN communicates with the LMN via which two pathways?

Answer 14

lateral pathway: for distal muscles

ventromedial pathway: for axial muscles

Question 15

What are the symptoms of LMN lesion?

Answer 15

reduced superficial reflex (withdraw reflex)
reduced tone
weakness/paralysis 
atrophy 
fasciculation

Question 16

What are the symptoms of UMN lesion?

Answer 16

spastic weakness
abnormal resting tone
hyperactive reflex 
clonus 
abnormal babinski 
loss of fine movements

Question 17

What does the lateral pathway include?

Answer 17

corticospinal tract

rubrospinal tract

Question 18

What does the ventromedial pathway include?

Answer 18

vestibulospinal tract
pontine reticulospinal tract
medullary reticulospinal tract
tectalspinal tract

Question 19

What does the vestibulospinal tract control?

Answer 19

postural maintenance

Question 20

what does the reticulospinal tract control?

Answer 20

maintains muscles of the midline for posture of the body

Question 21

what does the colliculospinal tract control?

Answer 21

reflex movement triggered by sound and vision. All information is integrated in the superior colliculus

Question 22

What does decerebrate mean?

Answer 22

without cerebellum

Question 23

What is decerebrate rigidity?

Answer 23

A rigid posture in an unconscious individual where extensors dominate on both upper and lower limbs

Question 24

What is decorticate rigidity?

Answer 24

rigid posture where lower limbs are extended and upper limbs are flexed

Question 25

What kind of cortical input does reticular formation receive?

Answer 25

tonic inhibition

Question 26

Reticulospinal tract is split into two separate paths. Name the two, and describe their function

Answer 26

medullary reticulospinal tract - control mostly the extensor muscles pontine reticulospinal tract - axial muscle control + postural control

Question 27

Which part of the midbrain contributes to lateral brain pathway?

Answer 27

red nucleus

Question 28

What is the role of red nucleus neurons

Answer 28

inhibition of mainly the flexors

Question 29

What causes decorticate rigidity

Answer 29

removal of activity from all cortical inputs, losing inhibition on both red nucleus and medullary reticulospinal tract. So arms flex and legs extend

Question 30

what causes decerebrate rigidity?

Answer 30

level of disruption is below the mid brain. Rubrospinal tract compromised, so flexors cannot be excited. Inhibition to reticulospinal tract lost, so extensors are overly active Extensors therefore dominate

Question 31

T/F decerebrate rigidity and progress to decorticate

Answer 31

False, lesion progress from midbrain to pons/medulla Can't go the other way because rubrospinal tract would have already been damaged

Question 32

What does an abnormal babinski sign mean?

Answer 32

brain no longer in normal control of the spinal cord

Question 33

Which nuclei in the brainstem do not receive bilateral inputs

Answer 33

hypoglossal and lower face

Question 34

What happens if you cut the LMN innervating facial muscles

Answer 34

unilateral and contralateral facial weakness

Question 35

what happens if you cut the UMN innervating facial muscles?

Answer 35

superior quadrant still receives ipsilateral input, so there is only unilateral, contralateral weakness in the inferior quadrant

Question 36

what is the aetiology of spastic movement from UMN lesion

Answer 36

you lose the anticipatory component of movement as well as disinhibiting LMN

Question 37

Where is the locomotor reflex circuit?

Answer 37

in the lumbar spinal cord

Question 38

Swing is mostly ______ activity | Stance is mostly ______ activity

Answer 38

flexor | extensor

Question 39

What senses the need to increase speed if there is no cortical control?

Answer 39

golgi tendon and muscle spindles provide the sensory input

Question 40

How does the muscle spindle increase the locomotion speed with increasing treadmill speed?

Answer 40

a sudden increase in flexor muscle will mean the extensor muscle is fully extended, therefore the cycle can be brought forward

Question 41

T/F during extensor activation, you get termination of flexor activity

Answer 41

True, because this is when the posture of the body is maintained, so flexing will only cause the individual to fall over

Question 42

What are the two types of gait abnormality

Answer 42

hemiparetic gait | circumducting gait

Question 43

What is the difference between hemiparetic and circumducting gait?

Answer 43

The location of lesion. Circumducting gait only affects the lower limb, whereas hemiparetic gait involves flexion of the upper limb and extension of the lower limb

Question 44

What kind of information does the motor association area encode?

Answer 44

complex movement the planning and the goal of movements the thought of movement

Question 45

What do the neurons in the motor cortex represent?

Answer 45

functionally relevant movements

Question 46

T/F if a muscle is active, then motor cortex neuron must be active

Answer 46

True, although the signal drops off a little bit

Question 47

What are mirror neurons

Answer 47

Neurons that integrate motor and visual signals. They fire when watching or doing/mirroring a particular action

Question 48

What is the purpose of having mirror neurons

Answer 48

they reflect our capacity of motor learning

Question 49

Where does the motor cortex get its inputs from?

Answer 49

prefrontal area (meaning of movement) motor association area (complex movement with a goal) somatosensory cortex (proprioception) central parietal area (recognising 3D surrounding space)

Question 50

In terms of visual signals, the dorsal stream is responsible for knowing ______ the object is, and the _______ action. On the other hand, the ventral stream is responsible for knowing ______ the object is, and the ______ action

Answer 50

what grasping where reaching

Question 51

what are the motor functions of basal ganglia?

Answer 51

complex movement selection and motor learning evaluating and improving movements initiation of movement

Question 52

In basal ganglia, the ______ is the C shape area around the ventricles, which wraps around the _______. These two are collectively known as ______, and ________ is found medial to it. The thalamus is medial to basal ganglia, but a component of basal ganglia, ________, can be found inferior to the thalamus. The last component is located in the brainstem, and it's called __________

Answer 52

``` caudate putamen striatum globus pallidus subthalamic nucleus substantia nigra ```

Question 53

Why is substantia nigra black?

Answer 53

because it produces melanin

Question 54

What is the appearance of the brain macroscopically in patients with Huntington's Disease?

Answer 54

abnormally large ventricle because caudate has degenerated from massive amount of neuronal death

Question 55

What are the four functions of the cerebellum?

Answer 55

optimise pattern of movement muscle tone maintenance motor learning (in smoothness of movement) planning sequence of movements

Question 56

How many lobes are in the cerebellum?

Answer 56

three

Question 57

What is the presentation of cerebellar anterior lobe syndrome

Answer 57

ataxic gait, loss of inter-limb coordination

Question 58

What is the test of ataxic gait?

Answer 58

slide heel down opposite shin

Question 59

What is the greatest risk factor of cerebellar anterior lobe syndrome?

Answer 59

chronic ethanol toxicity, which preferentially targets neurons in the anterior lobe

Question 60

What is the presentation of cerebellar posterior lobe syndrome

Answer 60

dysmetria (overshoot in precision reach) Dysdiadochokinesia (inability to rapidly alternate movements) Speech abnormality

Question 61

What is the presentation of flocculonodular lobe syndrome?

Answer 61

truncal ataxia

Question 62

How do we test for dysmetria?

Answer 62

ask the patient to alternative touching the nose and the doctor's hand

Question 63

How do we test for dysdiadochokinesia

Answer 63

the clapping test

Question 64

Describe the "double cross" of cerebellar pathway

Answer 64

Cerebellar damage affects the ipsilateral side, because the output to motor cortex is contralateral, but then the descending upper neuron decussates again