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Neurology Y2 > L14 - HARC: The Motor System - Clinico-anatomical correlations > Flashcards

L14 - HARC: The Motor System - Clinico-anatomical correlations Flashcards

1. Define the components of the basal ganglia - the nuclei and pathways 2. Describe and define the differences between an upper motor neuron and a lower motor neuron. 3. Describe and define the differences between an upper motor neuron lesion and a lower motor neuron lesion and their implications. 4. Describe how cranial nerve abnormalities can manifest - trigeminal neuralgia, facial palsy and disorders of the eye. 5. Be able to trace the pathways of the major sensory and motor pathways thro

1
Q

What is the function of Basal ganglia?

A

Control of movement.

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2
Q

Where are the Basal Ganglia located?

A

Forebrain and midbrain

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3
Q

Disorders in the Basal ganglia can lead to…

A

Abnormalities in:

  • motor control
  • posture
  • muscle tone
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4
Q

What are the components of the basal ganglia?

A
  • Putamen
  • Caudate nucleus
  • Globus Pallidus (2 parts)
  • Substantia Nigra (2 parts)
  • Subthalamic nucleus
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5
Q

Describe the neostratium?

A

Caudate + Putamen

- separated by anterior limb of internal capsule

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6
Q

What is the Nucleus accumbens associated with?

A
  • Reward and Gratificatio centres
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7
Q

How is the putamen separated from the globus pallidus?

A
  • thin lamina of nerve fibres known as the lateral medullary lamina.
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8
Q

What are the 2 divisions of the Globus Pallidus?

Pallidum

A 
GP external (lateral)
GP internal (medial)
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9
Q

Describe the pathways used by the Basal Ganglia?

A

Direct
- facilitates purposeful behaviour and movement

Indirect
- Inhibits unwanted movement

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10
Q

What is the internal capsule?

A

White matter tract pathway

- Boomerang shaped

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11
Q

What structures are lateral to the internal capsule?

A

Pallidum and Putamnen

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12
Q

What structures are medial to the internal capsule?

A 
Caudate nucleus (CN) 
Thalamus
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13
Q

Describe the structure of the internal capsule?

A
  1. Anterior Limb
    - frontopontine and thalamocortical fibres
  2. Genu
    - corticobulbar (corticonuclear) tract
  3. Posterior Limb
    - corticospinal tract
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14
Q

What is the blood supply to the Upper internal capsule?

A

Lateral striate aa.

Branches fro the Middle Cerebral artery.

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15
Q

Describe the blood supply to the lower internal capsule?

A 
Anterior Limb 
- medial striatea. from ACA 
Genu 
- Internal carotid artery branches 
Posterior Limb
- Anterior choroidal artery from middle cerebral artery.
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16
Q

Striatum and Pallidum

Distinguish which does output and which does input

A

Striatum - Input

Pallidum - Output

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17
Q

Describe the direct pathway?

A

BG removes inhibition of thalamus.

  • Promotes excitation of motor areas.
  • Increases activity
  • involves Globus Pallidus (internal)
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18
Q

Describe how Parkinson’s disease may occur?

A

Degeneration of dopamingeric neurons of substantia nigra.
Neuron loss in the Pars Compacta.
Depletion of striatal dopamine.

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19
Q

Describe the striatum?

A

Striatum consists: Caudate nucleus and putamen, connected across internal capsule
- Striatum receives cortical information

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20
Q

What provides inhibitory control during visual processing within the thalamus?

A

Release of GABA from local interneurons in the dorsal lateral geniculate nucleus.

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21
Q

In the direct pathway, what effect does the Basal Ganglia have on the thalamus?

A

Basal ganglia removes inhibition of thalamuss

  • promotes excitation of motor areas
  • increases activity
  • inhibition of the inhibition
  • involves globus pallidus internal
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22
Q

Describe how the basal ganglia reinforce thalamic inhibition?

A
  • Prevent excitation of motor areas by the thalamus.
  • decreases activity
  • promotes inhibition
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23
Q

What area of the Pallidum is iinvolved in the indirect pathway?

A

Globus Pallidus externus

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24
Q

Briefly describe how a basal ganglia disorder may arise?

A

Imbalance between direct and indirect pathway.
- Hypokinetic (Parkinson’s)
Excess indirect output, limited direct output
- Hyperkinetic (Huntington’s)
- Excess direct output, limited indirect output

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25
Q

What area of brain is involves in Parkinson’s disease?

A

Substantia Nigra

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26
Q

What pathway is affected in Parkinson’s disease?

A

Nigostriatal pathway

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27
Q

What are some key symptoms of Parkinson’s?

A

Resting tremor
Postural instability
Slowness of movement (Hypokinesia)

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28
Q

What kind of condition is Huntington’s disease?

A

Genetic condition.
Autosomal Dominant.
Hyperkinetic disorder characterised by involuntary movements.

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29
Q

How may Huntington’s disease arise?

A

Mutation of the Huntingtin protein.

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30
Q

How do UMN carry information from cerebral cortex?

A

Descending motor pathways

  • pyramidal tracts (generation of voluntary movement)
  • extrapyramidal tracts (coordination of voluntary movement)
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31
Q

What is the difference between the pyramidal tracts and extrapyramidal tracts?

A

Pyramidal tracts - generation of voluntary movement

Extrapyramidal tracts - coordination of voluntary movement

32
Q

State examples of pyramidal tracts?

A

Corticospinal

Corticobulbar

33
Q

State examples of Extrapyramidal tracts?

A

Rubrospinal
Reticulospinal
Vestibulospinal
Tectospinal

34
Q

Describe the corticospinal tract?

A

Fine voluntary motor control of limbs.

Pathway also controls voluntary body posture adjustments.

35
Q

Describe the corticobulbar tract?

A

Controls facial and masticatory musculature

movements of the tongue and swallowing.

36
Q

In the Cortictospinal tract where does the UMN synapse?

A

Required spinal cord level at the anterior motor horn.

37
Q

Where are the LMN carried in the corticospinal tract?

A

In spinal nerves

38
Q

In the corticobulbar tract where do the UMN synapse?

A

Brainstem

- cranial nerve nuclei

39
Q

Where are the LMN carried in the corticobulbar tract?

A

Cranial nerves

40
Q

Function of rubrospinal tract?

A

Involved in INVOL adjustment of arm position, in reposnse to balance information.
Support of the body.

41
Q

Function of reticulospinal tract?

A

Regulates various involuntary motor activities and assists in balance (leg extensors)

  • stepping
  • e.g. pattern movements
42
Q

Function of vestibulospinal tract?

A

Responsbile for adjusting posture to maintain balance.

43
Q

Function of Tectospinal tract?

A

Controls head and eye movements.

Involved in voluntary adjustment of head position in response to visual information.

44
Q

Where do upper motor neuron lesions occur?

A

CNS

  • brain
  • brainstem
  • spinal cord
45
Q

Where do lower motor neurons occur?

A

PNS

- cranial and spinal nerves

46
Q

What are some symptoms of lesions in upper motor neuron’s?

A
  • Muscle spasticity
  • weakness without muscle atrophy
  • More reflexes
  • Babinski sign
  • loss of superficial reflex
47
Q

Lesions affecting pyramidal tract will cause…

A

Loss of voluntary movement

but tone / coordination / posture is maintained.

48
Q

What are symptoms of a lesion in a lower motor neuron?

A
  • flaccid paralysis
  • hyporeflexia
  • muscle atrophy
  • hypotonicity
  • fasciculations
49
Q

A lesion affecting pyramidal and extrapyramidal systems will cause?

A

Voluntary movement and tone / coordination / posture compromised?

50
Q

Compare and contract UMN and LMN?

A

LMN lesion affects signal from both systems
- loss of voluntary movement
- loss of coordination, posture and tone
UMN affects movement signals not muscles themselves.
UMN - muscle atrophy through disuse, LMN through denervation
UMN cause muscle spasticity, LMN cause muscle flaccidity.

51
Q

Contrast the ways that lesions in either UMN or LMN can cause muscle atrophy?

A

UMN
- through disuse
LMN
- through denervation

52
Q

Superior oblique is innervated by?

A

CN IV

- trochlear

53
Q

Lateral rectus is innervated by?

A

CN VI

- abducent

54
Q

Inferior oblique & Inferior , superior and medial rectus is innervated by?

A

CN III

- occulomotor

55
Q

A lesion in CN III would cause?

A
  • loss of SR, IR, IO, MR action
  • Ptosis
  • loss of reflexes (accomodation and light)
56
Q

A lesion in CN IV would cause?

A

Loss of SO action

- diplopia

57
Q

A lesion in CN VI would cause?

A

Loss of LR action

- unopposed adduction of the eye.

58
Q

What are the three branches of the Trigeminal nerve?

A
  • Opthalmic V1 (s)
  • Maxillary V2 (s)
  • Mandibular V3 (m)

motor = muscles of mastication

59
Q

Can is the key symptom of a neuropathic disorder caused by either of the trigeminal branches?

A

INTENSE FACIAL PAIN

60
Q

What is Bell’s Palsy?

A 
Unknown facial paralysis. 
Unilateral.
Can occur overnight. 
- drooping of face 
- inability to close eye on affected side
61
Q

What are the 3 sensory ascending tracts?

A
  • Spinothalamic
  • Spinocerebellar
  • Dorsal Column / Medial lemniscus
62
Q

Where does the corticospinal tract run through?

A

Posterior limb of internal capsule.

63
Q

Where does decussation occur in the corticospinal tract?

A 
Medullary pyramids 
- 80% fibers decussate 
- lateral corticospinal tract 
20% no decussation 
- anterior corticospinal tract
64
Q

Where does the corticobulbar tract run through?

A
  • Runs through genu of internal capsule
65
Q

Describe decussation of the cranial nerves in the corticobulbar tract?

A 
Midbrain
- CN III, IV 
Pons
- CN V, VI, VII 
Medulla
- CN IX, X, XI, XII
66
Q

What does the spinothalamic tract detect?

A

Pain, pressure, touch and temperature

67
Q

What are the synapse points for the 1st, 2nd and 3rd order neurons respectively

A

Dorsal Horn - 1st
Thalamus - 2nd
Sensory cortex - 3rd

68
Q

What role does the spinocerebellar tract have?

A

Non-conscious proprioception

- position sense information from joint information

69
Q

Spinocerebellar tract consists of…

A

Ventral and dorsal tract

70
Q

Where does the ventral portion of the spinocerebellar tract enter?

A

Via superior cerebellar peduncle.

71
Q

Where does the dorsal portion of the spinocerebellar tract enter?

A

Dorsal enters via inferior cerebellar peduncle.

72
Q

What are the dorsal columns / medial lemniscus?

A

Ascending sensory pathway.
Dorsal columns
- cuneate fasciculus
- gracile fasciculus

73
Q

Describe the cuneate fasciculus?

A

Upper limb afferents

74
Q

Describe the gracile fasciculus?

A

Lower limb afferents

75
Q

Describe respectively where the 1s, 2nd and 3rd order neurons synapse in the dorsal columns?

A

Cuneate or gracile fasciculus 1st
Thalamus 2nd
Sensor cortex 3rd

76
Q

What are some functions of the dorsal columns?

A
  • conscious proprioception
  • fine touch
  • vibration
  • two-point discrimination

Neurology Y2 (24 decks)

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