Motor Cortical Control Flashcards
1
Q
What is the organisation like in motor control?
A
- Hierarchal organisation
- Functional segregation
2
Q
What does the hierarchal organisation mean?
A
- high order areas of hierarchy are involved in more complex tasks (programme and decide on movements, coordinate muscle activity)
- lower level areas of hierarchy perform lower level tasks (execution of movement)
3
Q
What is the functional segregation?
A
Motor system organised in a number of different areas that control different aspects of movement
4
Q
Where does the motor cortex receive information from? What happens to them?
A
- from cortical areas
- to thalamus and brainstem
5
Q
What does the cerebellum and basal ganglia do?
A
adjust commands received from other parts of motor control system
6
Q
What does the brainstem pass?
A
commands from cortex to spinal cord
7
Q
What are the two pyramidal tracts?
A
- Corticospinal
2. Corticobulbar
8
Q
What are pyramidal tracts?
A
major descending tracts
9
Q
What do the pyramidal tracts pass through?
A
pyramidsof the medulla
10
Q
What is the path of the pyramidal tracts?
A
motor cortex, spinal cord/cranial nerve nuclei in brainstem
11
Q
What type of movements are carried out by the pyramidal tract?
A
voluntary movements of body and face
12
Q
What are the 4 extrapyramidal tracts?
A
- Vestibulospinal
- Tectospinal
- Reticulospinal
- Rubrospinal
13
Q
Where do the extrapyramidal tracts pass?
A
not pass through thepyramidsof the medulla
14
Q
What is the journey of the extrapyramidal tracts?
A
Brainstem nuclei to spinal cord
15
Q
What sort of movements are in the extrapyramidal tracts?
A
involuntary (automatic) movements for balance, posture and locomotion
16
Q
What type of tract is the extrapyramidal tracts?
A
Major Descending
17
Q
Where is the primary motor cortex?
A
precentral gyrus - anterior to the central sulcus
18
Q
What does the primary motor cortex do?
A
- controls fine, discrete, precise voluntary movements.
2. Provides descending signals to execute movements.
19
Q
Where is the premotor area located?
A
anterior to primary motor cortex
20
Q
What is the premotor area involved in?
A
planning movements
21
Q
What does the premotor area regulate?
A
externally cued movements e.g. seeing an apple and reaching for it
22
Q
Where is the supplementary area located?
A
anterior and medial to primary motor cortex
23
Q
What is the supplementary area involved in?
A
planning complex movements (e.g. internally cued, speech)
24
Q
When does the supplementary are become active?
A
prior to voluntary movement
25
What makes up the lateral cortical spinal tract?
85-90% crossed fibres
26
What is the lateral corticospinal tract responsible for?
Limb muscle control
27
What makes up the anterior cortical spinal tract?
10-15% uncrossed fibres
28
What is the anterior corticospinal tract responsible for?
trunk muscles
29
What is the corticobulbar tract responsible for?
voluntary movements of the face and neck
30
What is in the primary motor cortex?
upper motor neurons
31
What is the oculomotor nucleus, trochlear nucleus and abducens nucleus involved in? (corticobulbar tract)
eye movements
32
What is the trigeminal motor nucleus responsible for? (corticobulbar tract)
muscles of the jaw
33
What is the facial nucleus responsible for? (corticobulbar tract)
muscles of the face
34
What is the hypoglossal nucleus responsible for? (corticobulbar tract)
tongue
35
What does the vestibulospinal tract do?
- lower motor neurons in vestibular nuclei
1. Stabilise head during body movements, or as head moves
2. Coordinate head movements with eye movements
3. Mediate postural adjustments
36
What is the reticulospinal tract?
Most primitive descending tract - from medulla and pons
37
What is the reticulospinal tract involved in?
1. Changes in muscles tone associated with voluntary movement
2. Postural stability
38
What does the tectospinal tract arise?
from superior colliculus of midbrain
39
What is the function of the tectopsinal tract?
Orientation of the head and neck during eye movements
40
What is the origin rubrospinal tract?
From red nucleus of midbrain
41
What does the rubrospinal tract do?
1. In humans mainly taken over by corticospinal tract
| 2. Innervate lower motor neurons of flexors of the upper limb
42
What are the negative signs in an upper motor neuron lesion?
1. Loss of voluntary motor function
2. Paresis: graded weakness of movements
3. Paralysis (plegia): complete loss of voluntary muscle activity
43
What are the positive sings in an upper motor neuron lesion?
1. Increased abnormal motor function due to loss of inhibitory descending inputs
2. Spasticity: increased muscle tone
3. Hyper-reflexia: exaggerated reflexes
4. Clonus: abnormal oscillatory muscle contraction
5. Babinski’s sign
44
What is apraxia?
- A disorder of skilled movement
| - Patients are not paretic but have lost information about how to perform skilled movements
45
When does apraxia happen?
- Lesion of
1. inferior parietal lob
2. the frontal lobe (premotor cortex, supplementary motor area - SMA)
- Stoke
- Dementia
46
Where are lower motor neurons found?
- Cranial nerve nuclei if corticobulbar tract
| - In spinal cord to innervate limb muscles for voluntary limb movement
47
How what are the symptoms of lower motor unit?
1. Weakness
2. Hypotonia (reduced muscle tone)
3. Hyporeflexia (reduced reflexes)
4. Muscle atrophy
5. Fasciculations
6. Fibrillations
48
What is a fasciculations?
damaged motor units produce spontaneous action potentials, resulting in a visible twitch
49
What are fibrillations?
spontaneous twitching of individual muscle fibres; recorded during needle electromyography examination
50
What is motor neuron disease (MND)?
Progressive neurodegenerative disorder of the motor system
| Spectrum of disorders (ALS)
51
What are upper motor neuron signs in MND?
1. Spasticity (increased tone of limbs and tongue)
2. Brisk limbs and jaw reflexes
3. Babinski’s sign
4. Loss of dexterity
5. Dysarthria (difficulty speaking)
6. Dysphagia (difficulty swallowing)
52
What are lower motor neuron signs in MND?
1. Weakness
2. Muscle wasting
3. Tongue fasciculations and wasting
53
What is the structure of the basal ganglia?
1. Caudate nucleus
2. Lentiform nucleus (putamen + external globus pallidus)
3. Nucleus accumbens
4. Subthalamic nuclei
5. Substantia nigra (midbrain)
6. Ventral pallidum, claustrum, nucleus basalis (of Meynert
54
What is the caudate and putamen collectively known as?
striatum, look at diagram
55
What is the function of the basal ganglia?
1. Decision to move
2. Elaborating associated movements (e.g. swinging arms when walking; changing facial expression to match emotions)
3. Moderating and coordinating movement (suppressing unwanted movements)
4. Performing movements in order
56
What areas are affected in MND?
1. Upper motor neurons
2. Brainstem lower motor neurons
3. Axon bundles
4. Intercostal muscles
5. Upper limb muscles
6. Tongue
7. Lower limb muscle
8. Spinal cord lower motor neurons
57
What happens in parkinsons?
Degeneration of the dopaminergic neurons that originate in the substantia nigra and project to the striatum
58
What is bradykinesia?
slowness of (small) movements (doing up buttons, handling a knife)
59
What is Hypomimic face
expressionless, mask-like (absence of movements that normally animate the face)
60
What is akinesia?
difficulty in the initiation of movements because cannot initiate movements internally
61
What is rigidity?
muscle tone increase, causing resistance to externally imposed joint movements
62
What is a tremor at rest?
4-7 Hz, starts in one hand (“pill-rolling tremor”); with time spreads to other parts of the body
63
What are the symptoms of Parkinson's disease?
1. Bradykinesia
2. Hypominimic face
3. Akinesia
4. Rigidty
5. Tremor at rest
64
What happens in Huntington's disease?
Degeneration of GABAergic neurons in the striatum, caudate and then putamen
65
What are the symptoms of Huntington's?
1. Choreic movements (chorea - dance)
rapid jerky involuntary movements of the body; hands and face affected first; then legs and rest of body
2. Speech impairment
3. Difficulty swallowing
4. Unsteady gait
5. Later stages, cognitive decline and dementia
66
What is the cause of Huntington's?
- Genetic neurodegenerative disorder
- Chromosome 4, autosomal dominant
- CAG repeat
67
When does Ballism usually happen?
stroke affecting the subthalamic nucleus
68
What is Ballism?
- Sudden uncontrolled flinging of the extremities
| - Symptoms occur contralaterally
69
Where is the cerebellum located?
posterior cranial fossa
70
How is the cerebellum separated from the cerebrum?
tentorium cerebelli
71
What is the function of the cerebellum?
Coordinator and predictor of movement
72
What is the function of the vestibulocerebellum?
1. Regulation of gait, posture and equilibrium
| 2. Coordination of head movements with eye movements
73
What does damage to the vestibulocerebellum cause?
(tumour) syndrome similar to vestibular disease leading to gait ataxia and tendency to fall (even when patient sitting and eyes open)
74
What is the function of the spinocerebellum?
1. Coordination of speech
2. Adjustment of muscle tone
3. Coordination of limb movements
75
What does damage to the spinocerebllum cause?
(degeneration and atrophy associated with chronic alcoholism) affects mainly legs, causes abnormal gait and stance (wide-based)
76
What is the function of the cerebrocerbellum?
1. Coordination of skilled movements
2. Cognitive function, attention,
processing of language
3. Emotional control
77
What does damage to the cerebrocerebellum cause?
affects mainly arms/skilled coordinated movements (tremor) and speech
78
What are the main signs of cerbellar dysfunction?
- Apparent only on movement
1. Ataxia
2. Dysmetria
3. Intention tremor
4. Dysdiadochokinesia
5. Scanning speech
79
What is ataxia?
General impairments in movement coordination and accuracy. Disturbances of posture or gait: wide-based, staggering (“drunken”) gait
80
What is dysmetria?
Inappropriate force and distance for target-directed movements (knocking over a cup rather than grabbing it)
81
What is intention tremor?
Increasingly oscillatory trajectory of a limb in a target-directed movement (nose-finger tracking)
82
What is dysdiadochokinesia?
Inability to perform rapidly alternating movements (rapidly pronating and supinating hands and forearms)
83
What is scanning speech?
Staccato, due to impaired coordination of speech muscles
