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Jonathan's Neuroscience > Motor Control > Flashcards

Flashcards in Motor Control Deck (64):
1

What is fibrillation

undetectable, unexpected movements of muscle sub-divisions

2

What is scanning speech caused by?

cerebellum lesion

3

Why does the NMJ have a "secure synapse"

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

4

Which muscles are recruited first when straining?

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

5

T/F Muscle strength grows in increments

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

6

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

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

7

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

25% of max force

8

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

fibrillation and fasciculation

9

What is fasciculation?

measurable, spontaneous twitching of muscle fibre

10

Why do muscles fibrillate?

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

11

What is the long term consequence of denervation?

atrophy and degeneration (irreversible

12

T/F muscles are inactive if not used

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

13

Which part of the brain regulates muscle tone?

cerebellum

14

The UMN communicates with the LMN via which two pathways?

lateral pathway: for distal muscles
ventromedial pathway: for axial muscles

15

What are the symptoms of LMN lesion?

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

16

What are the symptoms of UMN lesion?

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

17

What does the lateral pathway include?

corticospinal tract
rubrospinal tract

18

What does the ventromedial pathway include?

vestibulospinal tract
pontine reticulospinal tract
medullary reticulospinal tract
tectalspinal tract

19

What does the vestibulospinal tract control?

postural maintenance

20

what does the reticulospinal tract control?

maintains muscles of the midline for posture of the body

21

what does the colliculospinal tract control?

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

22

What does decerebrate mean?

without cerebellum

23

What is decerebrate rigidity?

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

24

What is decorticate rigidity?

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

25

What kind of cortical input does reticular formation receive?

tonic inhibition

26

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

medullary reticulospinal tract - control mostly the extensor muscles

pontine reticulospinal tract - axial muscle control + postural control

27

Which part of the midbrain contributes to lateral brain pathway?

red nucleus

28

What is the role of red nucleus neurons

inhibition of mainly the flexors

29

What causes decorticate rigidity

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

30

what causes decerebrate rigidity?

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

31

T/F decerebrate rigidity and progress to decorticate

False, lesion progress from midbrain to pons/medulla

Can't go the other way because rubrospinal tract would have already been damaged

32

What does an abnormal babinski sign mean?

brain no longer in normal control of the spinal cord

33

Which nuclei in the brainstem do not receive bilateral inputs

hypoglossal and lower face

34

What happens if you cut the LMN innervating facial muscles

unilateral and contralateral facial weakness

35

what happens if you cut the UMN innervating facial muscles?

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

36

what is the aetiology of spastic movement from UMN lesion

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

37

Where is the locomotor reflex circuit?

in the lumbar spinal cord

38

Swing is mostly ______ activity
Stance is mostly ______ activity

flexor
extensor

39

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

golgi tendon and muscle spindles provide the sensory input

40

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

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

41

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

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

42

What are the two types of gait abnormality

hemiparetic gait
circumducting gait

43

What is the difference between hemiparetic and circumducting gait?

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

44

What kind of information does the motor association area encode?

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

45

What do the neurons in the motor cortex represent?

functionally relevant movements

46

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

True, although the signal drops off a little bit

47

What are mirror neurons

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

48

What is the purpose of having mirror neurons

they reflect our capacity of motor learning

49

Where does the motor cortex get its inputs from?

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

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

what
grasping
where
reaching

51

what are the motor functions of basal ganglia?

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

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 __________

caudate
putamen
striatum
globus pallidus
subthalamic nucleus
substantia nigra

53

Why is substantia nigra black?

because it produces melanin

54

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

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

55

What are the four functions of the cerebellum?

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

56

How many lobes are in the cerebellum?

three

57

What is the presentation of cerebellar anterior lobe syndrome

ataxic gait, loss of inter-limb coordination

58

What is the test of ataxic gait?

slide heel down opposite shin

59

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

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

60

What is the presentation of cerebellar posterior lobe syndrome

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

61

What is the presentation of flocculonodular lobe syndrome?

truncal ataxia

62

How do we test for dysmetria?

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

63

How do we test for dysdiadochokinesia

the clapping test

64

Describe the "double cross" of cerebellar pathway

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