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Y2 Neuroscience and Mental Health > Cortical motor function, basal ganglia and cerebellum > Flashcards

Cortical motor function, basal ganglia and cerebellum Flashcards

1
Q

What is the location of the primary motor cortex

A

Precentral gyrus

Anterior to the central sulcus

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2
Q

What is the function of the primary motor cortex

A

Controls fine, discrete, precise, voluntary movement (input from cerebellum)
Provides descending signals to execute movement
Penfield’s motor homunculus

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3
Q

Describe the corticobulbar pathway (hypoglossal example)

A
  1. Originates from head region of motor cortex
  2. Passes through the internal capsule of basal ganglia
  3. Synapse in the medulla at the hypoglossal nucleus
  4. Hypoglossal nerve fibres pass out
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4
Q

Where is the premotor cortex found

A

Frontal lobe, anterior to primary motor cortex

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5
Q

What is the function of the premotor cortex

A

Planning of movements

Regulates externally cued movements

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6
Q

Where is the supplementary motor area

A

Frontal lobe, anterior to primary motor cortex, medially

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7
Q

What is the function of the supplementary motor area

A

Planning complex movements
Programming sequencing of movements
Regulates internally driven movements e.g. speech
Becomes active when thinking about a movement before executing it

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8
Q

What are the association cortexes

A

Brain areas whose activity does not correlate with motor output/act
Posterior parietal cortex - ensures movements are targeted accurately to objects in external space
Prefrontal cortex - involved in selection of appropriate movements for a particular course of action

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9
Q

Define lower motor neurone and upper motor neuron

A

Spinal cord, Brainstem

Corticospinal, corticobulbar

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10
Q

Define pyramidal and extrapyramidal

A

Lateral corticospinal tract

Basal ganglia, cerebellum

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11
Q

What is the consequence of an upper motor neuron lesion

A

Loss of function

  • Paresis: graded weakness of movements
  • Paralysis (plegia): complete loss of muscle activity

Increased abnormal motor function due to loss of inhibitory descending inputs

  • spasticity: increased muscle tone
  • Hyper-reflexia: exaggerated reflexes
  • Clonus: abnormal oscillatory muscle contraction

Babinski’s sign

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12
Q

What is apraxia

A

Disorder of skilled movement. Patients are not paretic but have lost information about how to perform skilled movements
Stroke and dementia most common causes

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13
Q

Which areas of the brain does apraxia involve

A

Lesion of the inferior parietal lobe, the frontal lobe (premotor cortex, supplementary motor area)

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14
Q

What are the clinical features of a lower motor neurone lesion

A 
Weakness
Hypotonia 
Hyporeflexia 
Muscle atrophy 
Fasciculations
Fibrillations
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15
Q

What are fasciculations

A

Damaged motor units produce spontaneous action potentials, resulting in a visible twitch

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16
Q

What are fibrillations

A

Spontaneous twitching of individual muscle fibres

Recorded during needle electromyography examination

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17
Q

What is motor neurone disease

A

Progressive neurodegenerative disorder of the motor system
Spectrum of disorders
Amyotrophic laurel sclerosis (ALS)

18
Q

What are the upper motor neuron signs of MND

A 
Increased muscle tone (spasticity of limbs and tongue)
Brisk limbs and jaw reflexes 
Babinski’s sign
Loss of dexterity
Dysarthria
Dysphagia
19
Q

What are the lower motor neurone signs of MND

A 
Weakness
Muscle wasting
Tongue fasciculations and wasting
Nasal speech
Dysphagia
20
Q

What makes up the basal ganglia

A

Caudate nucleus
Lentiform nucleus (putamen + external globus pallidus)
Subthalamic nucleus
Substantia nigra
Ventral pallidum, claustrum, nucleus accumbens, nucleus basalis of Meynert

21
Q

What are the functions of the basal ganglia

A

Elaborating associated movements (e.g. swinging arms when walking; changing facial expression to match emotions)

Moderating and coordinating movement (suppressing unwanted movements)

Performing movements in order

22
Q

Describe the circuitry of the basal ganglia

A

cortex -> globus pallidus, striatum, substantia nigra

Globus pallidus -> subthalamic nucleus -> globus pallidus -> thalamus -> SMA -> substantia nigra (C) -> substantia nigra (r)

23
Q

What is the neuropathology of parkinson’s

A

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

24
Q

What are some clinical features of Parkinson’s

A 
Shaking palsy (paralysis agitans)
Involuntary motion, with lessened muscular power 
Propensity to bend the trunk forward  and to pass from a walking to a running pace
25
Q

What are the main motor signs of Parkinson’s

A

Bradykinesia (slowness of small movements)
Hypomimic face (expressionless)
Akinesia (difficulty in initiation of movements)
Rigidity (increased muscle tone)
Tremor at rest (4-7Hz, in one hand then other body parts)

26
Q

Describe the nigro-striatal pathway

A

-

27
Q

Describe Huntington’s disease

A

Genetic neurodegenerative disorder
Chromosome 4, autosomal dominant
CAG repeat (>35)
Degeneration of GABAergic neurons in the striatum, caudate and then putamen

28
Q

What are the motor signs of Hungtington’s disease

A 
Choreic movements (chorea)
Speech impairment
Difficulty swallowing 
Unsteady gait
Later - cognitive decline and dementia
29
Q

What are choleric movements

A

Rapid jerky involuntary movements of the body; hands and face affected first; then legs and rest of body

30
Q

How are purkinje cells connected to other cells in the cerebllum

A

Inferior olive projects to purkinje cells via climbing fibres
All other inputs to fragile cells are via mossy fibres and then parallel fibres onwards
All output from purkinje cells are via deep nuclei

31
Q

What are the divisions of the cerebellum

A

Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum

32
Q

Describe the vestibulocerebellum

A

Regulation of gait, posture and equilibrium

Coordination of head movements with eye movements

33
Q

Describe the spinocerebellum

A

Coordination of speech
Adjustment of muscle tone
Coordination of limb movements

34
Q

Describe the cerebrocerebellum

A

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

35
Q

Describe Vestibulocerebellar Syndrome

A

Damage (tumour) causes syndrome similar to vestibular disease leading to gait ataxia and tendency to fall (even when patient sitting and eyes open)

36
Q

Describe Spinocerebellar syndrome

A

Damage (degeneration and atrophy associated with chronic alcoholism) affects mainly legs, causes abnormal gait and stance (wide-based)

37
Q

Describe Cerebrocerebellar or Lateral Cerebellar Syndrome

A

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

38
Q

What are the main signs of cerebellar dysfunction

A

Ataxia - general impairments in coordination and accuray
Dysmetria - inappropriate force and distance
Intention tremor - increasingly oscillatory trajectory of a limb
Dysdiadochokinesia - inability to perform rapidly alternating movements
Scanning speech - staccato, due to impaired coordination of speech muscles

39
Q

Describe the motor system hierarchy

A

-

40
Q

Describe the motor homunculus

A

From centre in - Leg, arm, face, tongue

41
Q

Describe the lateral corticospinal pathway

A
  1. Primary motor cortex
  2. Fibres pass down pass through the internal capsule of the basal ganglia
  3. Descent down through the midbrain and pons
  4. In the Medullary pyramids the fibres cross over (decussation, no synapse)
  5. Descent through the spinal cord in the lateral corticospinal tract
  6. Projection to the ventral root in the relevant spinal level
42
Q

Describe the anterior corticospinal pathway

A
  1. Primary motor cortex
  2. Fibres pass down pass through the internal capsule of the basal ganglia
  3. Descent down through the midbrain and pons
  4. Through the medulla
  5. Descent through the spinal cord in the anterior corticospinal tract
  6. Decussation at the level of the spinal cord

Y2 Neuroscience and Mental Health (22 decks)

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