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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
What area of brain is involves in Parkinson's disease?
Substantia Nigra
26
What pathway is affected in Parkinson's disease?
Nigostriatal pathway
27
What are some key symptoms of Parkinson's?
Resting tremor Postural instability Slowness of movement (Hypokinesia)
28
What kind of condition is Huntington's disease?
Genetic condition. Autosomal Dominant. Hyperkinetic disorder characterised by involuntary movements.
29
How may Huntington's disease arise?
Mutation of the Huntingtin protein.
30
How do UMN carry information from cerebral cortex?
Descending motor pathways - pyramidal tracts (generation of voluntary movement) - extrapyramidal tracts (coordination of voluntary movement)
31
What is the difference between the pyramidal tracts and extrapyramidal tracts?
Pyramidal tracts - generation of voluntary movement Extrapyramidal tracts - coordination of voluntary movement
32
State examples of pyramidal tracts?
Corticospinal | Corticobulbar
33
State examples of Extrapyramidal tracts?
Rubrospinal Reticulospinal Vestibulospinal Tectospinal
34
Describe the corticospinal tract?
Fine voluntary motor control of limbs. Pathway also controls voluntary body posture adjustments.
35
Describe the corticobulbar tract?
Controls facial and masticatory musculature movements of the tongue and swallowing.
36
In the Cortictospinal tract where does the UMN synapse?
Required spinal cord level at the anterior motor horn.
37
Where are the LMN carried in the corticospinal tract?
In spinal nerves
38
In the corticobulbar tract where do the UMN synapse?
Brainstem | - cranial nerve nuclei
39
Where are the LMN carried in the corticobulbar tract?
Cranial nerves
40
Function of rubrospinal tract?
Involved in INVOL adjustment of arm position, in reposnse to balance information. Support of the body.
41
Function of reticulospinal tract?
Regulates various involuntary motor activities and assists in balance (leg extensors) - stepping - e.g. pattern movements
42
Function of vestibulospinal tract?
Responsbile for adjusting posture to maintain balance.
43
Function of Tectospinal tract?
Controls head and eye movements. | Involved in voluntary adjustment of head position in response to visual information.
44
Where do upper motor neuron lesions occur?
CNS - brain - brainstem - spinal cord
45
Where do lower motor neurons occur?
PNS | - cranial and spinal nerves
46
What are some symptoms of lesions in upper motor neuron's?
- Muscle spasticity - weakness without muscle atrophy - More reflexes - Babinski sign - loss of superficial reflex
47
Lesions affecting pyramidal tract will cause...
Loss of voluntary movement | but tone / coordination / posture is maintained.
48
What are symptoms of a lesion in a lower motor neuron?
- flaccid paralysis - hyporeflexia - muscle atrophy - hypotonicity - fasciculations
49
A lesion affecting pyramidal and extrapyramidal systems will cause?
Voluntary movement and tone / coordination / posture compromised?
50
Compare and contract UMN and LMN?
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
Contrast the ways that lesions in either UMN or LMN can cause muscle atrophy?
UMN - through disuse LMN - through denervation
52
Superior oblique is innervated by?
CN IV | - trochlear
53
Lateral rectus is innervated by?
CN VI | - abducent
54
Inferior oblique & Inferior , superior and medial rectus is innervated by?
CN III | - occulomotor
55
A lesion in CN III would cause?
- loss of SR, IR, IO, MR action - Ptosis - loss of reflexes (accomodation and light)
56
A lesion in CN IV would cause?
Loss of SO action | - diplopia
57
A lesion in CN VI would cause?
Loss of LR action | - unopposed adduction of the eye.
58
What are the three branches of the Trigeminal nerve?
- Opthalmic V1 (s) - Maxillary V2 (s) - Mandibular V3 (m) motor = muscles of mastication
59
Can is the key symptom of a neuropathic disorder caused by either of the trigeminal branches?
INTENSE FACIAL PAIN
60
What is Bell's Palsy?
``` Unknown facial paralysis. Unilateral. Can occur overnight. - drooping of face - inability to close eye on affected side ```
61
What are the 3 sensory ascending tracts?
- Spinothalamic - Spinocerebellar - Dorsal Column / Medial lemniscus
62
Where does the corticospinal tract run through?
Posterior limb of internal capsule.
63
Where does decussation occur in the corticospinal tract?
``` Medullary pyramids - 80% fibers decussate - lateral corticospinal tract 20% no decussation - anterior corticospinal tract ```
64
Where does the corticobulbar tract run through?
- Runs through genu of internal capsule
65
Describe decussation of the cranial nerves in the corticobulbar tract?
``` Midbrain - CN III, IV Pons - CN V, VI, VII Medulla - CN IX, X, XI, XII ```
66
What does the spinothalamic tract detect?
Pain, pressure, touch and temperature
67
What are the synapse points for the 1st, 2nd and 3rd order neurons respectively
Dorsal Horn - 1st Thalamus - 2nd Sensory cortex - 3rd
68
What role does the spinocerebellar tract have?
Non-conscious proprioception | - position sense information from joint information
69
Spinocerebellar tract consists of...
Ventral and dorsal tract
70
Where does the ventral portion of the spinocerebellar tract enter?
Via superior cerebellar peduncle.
71
Where does the dorsal portion of the spinocerebellar tract enter?
Dorsal enters via inferior cerebellar peduncle.
72
What are the dorsal columns / medial lemniscus?
Ascending sensory pathway. Dorsal columns - cuneate fasciculus - gracile fasciculus
73
Describe the cuneate fasciculus?
Upper limb afferents
74
Describe the gracile fasciculus?
Lower limb afferents
75
Describe respectively where the 1s, 2nd and 3rd order neurons synapse in the dorsal columns?
Cuneate or gracile fasciculus 1st Thalamus 2nd Sensor cortex 3rd
76
What are some functions of the dorsal columns?
- conscious proprioception - fine touch - vibration - two-point discrimination

Neurology Y2 (24 decks)

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