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NEUROLOGY AND NEUROSCIENCE 2 > MOTOR CORTICAL CONTROL > Flashcards

MOTOR CORTICAL CONTROL Flashcards

1
Q

What us the hierarchical organisation of motor control

A

High order areas of hierarchy are involved in more complex tasks (programme and decide on movements, coordination)

Lower level areas of hierarchy perform lower level tasks (execution of movement)

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2
Q

How is the motor system organised?

A

By functional segregation

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3
Q

Name the descending pyramidal tracts

A

Corticospinal
Corticobulbar

Voluntary movements of body and face

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4
Q

Name the extra pyramidal tracts

A

Vestibulospinal
Tectospinal
Reticulospinal
Rubrospinal

Involuntary movements for balance, posture and locomotion

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5
Q

Describe the decussation of the corticospinal tract

A

85-90% decussate to the lateral corticospinal tract

10-15% remain on same side via anterior corticospinal tract

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6
Q

What does the lateral corticospinal and anterior corticospinal tract innervate?

A

Lateral - limb muscles

Anterior - trunk muscle

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7
Q

What does the corticobulbar tract do?

A

Principal motor pathway for voluntary movements of the face and neck

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8
Q

What does the vestibulospinal tract do?

A

Stabilises head during body movements or as head moves
Coordinate head movements with eye movements
Mediate postural adjustments

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9
Q

What does the reticulospinal tract do?

A

Changes in muscle tone associated with voluntary movement
Postural stability

Descends from medulla and pons

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10
Q

What does the tectospinal tract do? And where does it descend from?

A

Orientation of head and neck during eye movements

Descends from superior colliculus of midbrain

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11
Q

What does the rubrospinal tract do?

A

In humans mainly taken over by corticospinal tract
Innervates lower motor neurons in flexors of upper limb

Descends from red nucleus of midbrain

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12
Q

What does an upper motor neuron lesion cause?

A

Negative signs:

  • Loss of voluntary motor function
  • Paresis (graded weakness of movements)
  • Paralysis
Positive signs:
- Increased abnormal motor function due to loss of 
  inhibitory descending inputs
- Spasticity (increased muscle tone)
- Hyper-reflexia
- Clonus
- Babinski's sign
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13
Q

What is apraxia and what could cause it?

A

Disorder of skilled movement. Not paretic but patients have lost info on how to perform skilled movements

Lesions/diseases of:

  • inferior parietal lobe
  • frontal lobe (premotor cortex/supplementary motor area)
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14
Q

What are the most common diseases causing apraxia?

A

Stroke and dementia

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15
Q

What does a lower motor neuron lesion cause?

A 
Weakness
Hypotonia
Hyporeflexia
Muscle atrophy
Fasciculations
Fibrillations
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16
Q

What are fasciculations?

A

Damaged motor units which produce spontaneous APs resulting in a visible twitches

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17
Q

What are fibrillations?

A

Spontaneous twitching of individual muscle fibres recorded during needle electromyography examination

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18
Q

What is motor neuron disease (MND)?

A

Spectrum of progressive neurodegenerative disorder affecting upper and lower motor neurones

AKA amyotrophic lateral sclerosis (ALS)

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19
Q

What are the upper motor neuron symptoms of MND?

A 
Spasticity
Brisk limbs and jaw reflexes
Babinski's sign
Loss of dexterity
Dysarthria
Dysphagia
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20
Q

What are the lower motor neuron symptoms of MND

A 
Weakness
Muscle wasting
Tonge fasciculations and wasting
Nasal speech
Dysphagia
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21
Q

List the nuclei in the basal ganglia

A

Caudate nucleus
Putamen (caudate and putamen together called striatum)
Lentiform nucleus
Nucleus accumbens
Subthalamic nuclei
Substantia nigra
Ventral pallidum, claustrum, nucleus basalis

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22
Q

What is the function of the caudate nucleus?

A

Decision to move

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23
Q

Which nuclei are responsible for elaborating associated movements e.g. swinging arms when walking, changing facial expression to match emotion

A

Lentiform nucleus (putamen + external globus pallidus)

Nucleus accumbens

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24
Q

What is the function of the substantia nigra?

A

Moderating and coordinating movement (suppressing unwanted movement)

25
Q

Which parts of the basal ganglia circuitry are affected in Parkinson’s disease, Huntington’s disease and Ballism?

A

Parkinson’s disease - between striatum and substantia nigra (rostral)

Huntington’s disease - striatum leading to globus pallidus

Ballism - subthalamic nucleus

26
Q

What is Parkinson’s disease?

A

Degeneration of the dopaminergic neurons that originate in the substantia nigra and project to the striatum

27
Q

List the symptoms of Parkinson’s disease

A

Bradykinesia - slowness of small movements
Hypomimic face - expressionless, mask-less
Akinesia - difficulty in the initiation of movements because cannot initiate movements internally
Rigidity - muscle tone increase causing resistance to joints
Tremor at rest - 4-7 Hz starting in one hand with time spreading to other parts of body “pill rolling tremor”

28
Q

What is pathology of Huntington’s disease?

A

Genetic degeneration of the GABAergic neurons in the striatum, caudate and then putamen

29
Q

Describe the genetic mutation which causes Huntington’s disease

A

Chromosome 4
Autosomal dominant
CAG repeat

30
Q

What are the symptoms of Huntington’s disease?

A

Choreic movements - jerky movements of hands and face affected first then legs and rest of body
Speech impairment
Dysphagia
Unsteady gait
Cognitive decline and dementia in later stages

31
Q

What is ballism?

A

Sudden uncontrolled flinging of the extremities

Usually caused by stroke affecting subthalamic nucleus with symptoms occuring on contralateral side

32
Q

What is the function of the cerebellum?

A

Coordinator and predictor of movement

Takes signals on their way down and compares it with sensory signals from receptors on their way up to coordinate movements and make them fluid

33
Q

Name the 3 parts of the cerebellum and point them out on a diagram

A

Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum

34
Q

What is the function of the vestibulocerebellum?

A

Regulation of gait, posture and equilibrium

Coordination of head movements with eye movements

35
Q

What is the function of the spinocerebellum?

A

Coordination of speech
Adjustment of muscle tone
Coordination of limb movements

36
Q

What is the function of the cerebrocerebellum?

A

Coordination of skilled movements
Cognitive function, attention, processing of language
Emotion control

37
Q

What does damage e.g. tumour in vestibulocerebellum cause?

A

Syndrome similar to vesitbular disease:

- gait, ataxia and tendency to fall

38
Q

What does damage (e.g. chronic alcoholism causing degeneration and atrophy) in spinocerebellum cause?

A

Affects mainly legs causing abnormal gait and wide-based stance

39
Q

What does damage to cerebrocerebellum cause?

A

Damage affects mainly arms/skilled coordinated movements (tremor) and speech

40
Q

List the main signs of cerebellar dysfunction

A 
Ataxia
Dysmetria
Intention tremor
Dysdiadockokinesia
Scanning speech
41
Q

What is the difference between extrafusal and intrafusal muscles

A

Extrafusal - muscle fibres have contractile elements in them

Intrafusal - muscle fibres which contain the sensory organs which respond to stretch and tension. Responsible for conveying the sensory info about the status of a muscle

42
Q

What is an alpha motor neuron?

A

The lower motor neurons of the brainstem and spinal cord which innervate the extrafusal muscle fibres of the skeletal muscles.

43
Q

Which part of the spinal cord do alpha motor neurons occupy?

A

Ventral horn

44
Q

What is a motor neuron pool?

A

All the alpha motor neurons that innervate a single muscle

45
Q

What are the two mechanisms in which the brain regulates the amount of force that a muscle produces?

A

Recruitment - Smaller units recruited and derecruited first allowing fine control

Rate coding - The more a motor unit fires the greater the force produced. Slow units fire at a lower frequency.

46
Q

What causes muscle fibre type IIB - IIA change?

A

Training e.g. gym

47
Q

What causes type I to II?

A

Severe deconditioning:

  • Spinal cord injury
  • Astronauts due to microgravity
48
Q

What happens to motor units in ageing?

A

Loss of type I and II

Preferential loss of type II thus greater proportion of I

49
Q

What are descending (supraspinal) control of reflexes

A

Higher centres of CNS exert inhibitory control on stretch reflex

Reflexes can be influenced by specific motions which remove the descending inhibition from the brain causing the reflex to become larger

50
Q

What is the Jendrassik manoeuvre?

A

Clenching teeth, making a fist, pulling against locked fingers causes the patellar tendon reflex to be larger

51
Q

What is decerebration?

A

Surgery to separate cortex from lower brain stem and spinal cord regions

Shows that excitatory control (inhibition) comes from higher centres of CNS. Without the higher centres only lower centres left causing rigidity and spasticity giving over-active and tonic stretch reflex

52
Q

List the 5 types neurons which control reflexes

A 
Activating alpha motor neurons
Activating inhibitory interneurons
Activating propriospinal neurons
Activating gamma motor neurons
Activating terminals of afferent fibres
53
Q

What are activating propriospinal neurons

A

Interneurons which go up and down to activate nearby muscles to help with movement

54
Q

What are gamma motor neurons

A

Alter the sensory organs that are housed in intrafusal muscles. Allows the muscle to remain sensitive to stretch when muscle at different lengths

55
Q

What is clonus?

A

Form of hyper-reflexia - involuntary and rhythmic muscle contractions

56
Q

What is Babinski’s sign?

A

When sole of foot stimulated with blunt instrument the big toe curls upwards when it normally curls downwards

Associated with upper corticospinal tract neuron lesion

57
Q

Why does Babinski’s sign not work in infants?

A

Their big toe will curl upwards due to an undeveloped corticospinal tract

58
Q

Why does hyper-reflexia occur?

A

Loss of descending inhibition

Upper motor neuron lesion

59
Q

Why does hypo-reflexia occur?

A

Lower motor neuron diseases as efferent limb of reflex not functioning

NEUROLOGY AND NEUROSCIENCE 2 (9 decks)

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