Motor control & movement disorders Flashcards

1
Q

what are the main principles of motor control?

A

hierarchical organisation and functional segregation

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2
Q

what is hierarchical organisation?

A

higher order areas = more complex tasks e.g planning

lower level areas = lower level tasks e.g movement execution

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3
Q

what is functional segregation in terms of motor control?

A

motor system is organised in a number of different areas that control different aspects of motion ie basal ganglia, brainstem etc

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4
Q

what are the major descending tracts?

A

pyramidal and extrapyramidal tracts

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5
Q

what is the function of the pyramidal tract?

A

voluntary movements of body and face

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6
Q

what is contained within the pyramidal tracts

A

corticospinal and corticobulbar

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7
Q

what is contained within the extrapyramidal tracts?

A

Vestibulospinal
Reticulospinal
Tectospinal
Rubrospinal

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8
Q

what is the pathway for pyramidal tracts?

A

pass through pyramids of the medulla

motor cortex to spinal cord or cranial nerve nuclei in brainstem

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9
Q

what is the pathway for extrapyramidal tracts?

A

brainstem nuclei to spinal cord

do not pass through pyramids of the medulla

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10
Q

where is the area for primary motor control

A

precentral gyrus

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11
Q

what is the role of the primary motor cortex?

A

controls fine, discrete precise voluntary movement - descending signals for execution

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12
Q

where is the premotor control area?

A

anterior to primary motor cortex but not up to top of brain

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13
Q

what is the role of the premotor area?

A

planning movements, regulating externally cued movements (reactions to environment e.g catching an apple)

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14
Q

where is the supplementary motor area?

A

above premotor area extending to longitudinal fissure

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15
Q

what is the role of the supplementary motor area?

A

planning complex movements and regulating internally cued movements (things you think about before doing it e.g speech)
active prior to voluntary movements

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16
Q

what is the corticospinal tract split into?

A

lateral (limb muscles) and anterior (trunk) corticospinal tract

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17
Q

which corticospinal fibres cross in the pyramids of decussation?

A

lateral corticospinal tract (85-90%) of corticospinal

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18
Q

which corticospinal fibres don’t decussate in the pyramids?

A

anterior corticospinal tract (10-15%)

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19
Q

what is the function of the corticobulbar tract?

A

principle motor pathway for voluntary movements in the face and neck

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20
Q

what nuclei do eye movements originate from?

A

oculomotor, trochlear and abducens nucleus

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21
Q

what nucleus controls the muscles of the jaw?

A

trigeminal motor nucleus

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22
Q

what nucleus controls the muscles of the face?

A

facial nucleus

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23
Q

what nucleus controls the tongue?

A

hypoglossal nucleus

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24
Q

what is the role of the vestibulospinal tract?

A

stabilise head during body/head movements
coordinates head & eye movement
mediates postural adjustments

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25
what is the role of the reticulospinal tract?
changes in muscle tone associated with voluntary movement | postural stability
26
what is the role of the tectospinal tract?
orientation of the head and neck during eye movements
27
what is the role of the rubrospinal tract?
innervate lower motor neurones of flexors of upper limb (mainly taken over by corticospinal)
28
what are the negative signs of upper motor neuron lesions?
loss of voluntary motor function paresis paralysis (plegia)
29
what are the positive signs associated with upper motor neuron lesions?
``` increased abnormal motor function inhibitory descending inputs spasticity hyperreflexia clonus babinskis sign ```
30
what are the signs of a lower motor neuron lesion?
``` weakness hypotonia/reflexia muscle atrophy fasciculations fibrillations ```
31
what is apraxia?
disorder of skilled movement caused by lesion of inferior parietal lobe or frontal lobe (premotor and supplementary areas)
32
what is motor neuron disease also known as?
ALS (amyotrophic lateral sclerosis)
33
what is ALS?
progressive degenerative disorder spectrum of NS
34
what are the upper motor neuron signs of ALS?
``` spasicity brisk limbs and jaw reflexes babinskis sign loss of dexterity dysarthria (difficulty speaking) dysphagia ```
35
what are the lower motor neuron signs of ALS?
``` weakness muscle wasting tongue fasciculations and wasting nasal speech dysphagia ```
36
what does the basal ganglia consist of?
caudate nucleus lentiform nucleus (putamen+external globus pallidus) nucleus accumbens subthalamic nucleus substantia nigra ventral pallidum, claustrum, nucleus basalis
37
what is the striatum?
caudate and putamen combined
38
what is the function of the basal ganglia?
decision to move elaborating associated movements e.g arm swing when walking moderating and coordinating movement performing movements in order
39
what is parkinsons disease?
degeneration of dopaminergic neurons originating in substantia nigra and project to striatum
40
what are the symptoms of parkinsons disease?
``` bradykinesia, akinesia rigidity resting tremor/pin roll tremor shuffling gait hypomimic face ```
41
what is a hypomimic face? (parkinsons)
expressionless, mask-like face (absence of facial animation)
42
what is huntingtons disease?
degeneration of GABAergic neurons in striatum, caudate and putamen
43
what is the genetic component of huntingtons disease?
neurodegenerative - chromosome 4 abnormal dominant (CAG repeat)
44
what are the symptoms of huntingtons disease?
``` hyperkinesia/choreic movements speech impairment difficulty swallowing unsteady gait cognitive decline and dementia eventually ```
45
what is ballism?
sudden, uncontrolled flinging of extremities
46
what is ballism the result of?
usually stroke subthalamic nucleus | symptoms appear contralaterally
47
what is the function of the cerebellum/
coordinator and predictor of movement
48
what is the function of the vestibulocerebellum?
gait, posture and equilibrium | coordinates head & eye movement
49
what does damage to the vestibulocerebellum cause
ataxia, tendency to fall even with eyes open and sat down
50
what is the function of the spinocerebellum?
speech coordination, adjustment of muscle tone and coordination of limb movement
51
what is a common cause of damage to the spinocerebellum?
degeneration and atrophy associated with chronic alcoholism
52
what does damage to the spinocerebellum present as?
abnormal gait and wide based stance
53
what is the function of the cerebrocerebellum?
``` coordination of skilled movement, cognitive function, attention, language processing, emotional control ```
54
what does damage to the cerebrocerebellum present as?
mainly arms - skilled coordinated movement tremor and speech issues
55
what is ataxia?
general impairment in movement coordination and accuracy, disturbances of posture/gait
56
what is dysmetria?
inappropriate force and distance for target-directed movements
57
what is an intention tremor?
increasingly oscillatory trajectory of limb in target-directed movements
58
what is dysdiadochokinesia?
inability to perform rapidly alternating movements
59
what is scanning speech?
staccato, impaired coordination of speech muscles
60
what are the signs of cerebellar dysfunction?
``` ataxia dysmetria intention tremor dysdiadochokinesia scanning speech ```
61
what are alpha motor neurons
lower motor neurons of the brainstem and spinal cord that innervate extrafusal muscle fibres of skeletal muscle, responsible for reflex actions
62
what is a motor unit?
a single neuron and all the muscles it innervates | smallest functional unit with which to produce force
63
what are the main classifications of muscle fibre
slow S type I fast fatigue resistant FR type IIA fast fatiguable FF type IIB
64
what are the features of type I muscle fibres?
smallest diameter cell bodies small dendritic trees thinnest axons slowest conduction velocity
65
what are the features of type IIA muscle fibres?
larger diameter cell bodies larger dendritic trees thicker axons faster conduction velocity fast fatigue resistant
66
what are the features of type I muscle fibre contractions?
least force, slow to contract but maximal force is maintained
67
what are the features of a type IIA muscle fibre contraction? (fast fatigue resistant)
more force, fairly fast contraction but held for long time
68
what are the features of a type IIB muscle fibre contraction?
most force, fast contraction but fairly short
69
what are the mechanisms by which the brain regulates force of a single muscle?
recruitment - number of motor units involved | rate coding - how fast the units contract
70
what is the principle of recruitment for muscle fibres?
size principle - smaller units recruited first(usually slow twitch fibres), as more force is required, more units recruited allows fine control when low force levels are required
71
what is rate coding?
motor unit has a range of frequencies they can fire at as rate firing increases, force produced by the unit increases - summation occurs when units fire at frequency too fast to allow the muscle to relax between arriving action potentials muscle fibres are unrecruited in the order they were recruited
72
what is the significance of neurotrophic factors?
motor unit and fibre characteristics are dependent on the nerve which innervates them this shows plasticity
73
when is the most common change of IIB to IIA?
muscular endurance training
74
what can cause a change of I to II fibres?
spaceflight spinal cord injury (deconditioning)
75
how does ageing affect muscle fibre types?
preferential loss of fast muscles (type II)
76
describe the course of a monosynaptic reflex?
sensory receptor - sensory neuron - motor neuron = action
77
what is the jendrassik manoeuvre?
creating larger reflexes by clenching teeth, making a fist, pulling against locked fingers and then testing a reflex
78
what is hyperreflexia associated with?
upper motor neuron lesions (loss of inhibition)
79
what is clonus?
rhythmic involuntary muscle contraction after manual stretch
80
what is the babinski sign?
sole of foot stimulated by blunt instrument (stroked) the big toe should react
81
what is a positive babinski sign?
big toe curls upwards (but normal in infants)
82
pathway for corticospinal tract
motor cortex (from motor homunculus) to cerebral peduncle in medulla pyramids - anterior stays ipsilateral, lateral goes contralateral (lateral =limbs) travel through spinal cord as anterior or lateral corticospinal tracts synapse in ventral horn of spinal level they exit at continue as lower motor neurons