Control Of Movement Flashcards

1
Q

What is motor control?

A
  • Refers to brain mechanisms that produce purposeful, coordinated movements
  • The brain adapts motor outputs to responds to changing sensory inputs from the body and the external environments
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2
Q

Which structures of the brain are involved in motor control?

A
  • Prefrontal cortex
  • Pareital cortex
  • Cerebellum
  • Brainstem centres
  • Spinal cord
  • Key structure: Basal ganglia which is connected to all of these structures
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3
Q

What are the structures of the basal ganglia?

A
  • Stratium: Caudate Nucleus & Putamen
  • Globus pallidus
  • Subthalamic nucleus
  • Substantia nigra
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4
Q

What type of connections does the basal ganglia receive?

A
  • Receives afferent and efferent connections
  • A: Basal ganglia major structures, MD medial dorsal, VA ventral dorsal, ventral nuclei of thalamus
  • B: Major afferents to basal ganglia
  • C: Intrinsic connections
  • D: Efferent connections
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5
Q

How does the basal ganglia work in regards to motor control?

A

The basal ganglia takes massive inputs from multiple cortical and brainstem regions and output to selected parts of these same areas
- Initiation of movement
- Focussing function
- Scaling movement: Amplitude, Velocity, rhythm

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6
Q

What does the Basal ganglia do?

A
  • Integrate diverse inputs from the entire cerebral cortex and funnel these influence via the thalamus to the motor cortex
  • Focus attention on what is relevant among the plethora of activities going on at any time
  • Favours certain channel activity over others
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7
Q

What arises due to the abnormal function of the basal ganglia?

A

Movement disorders
- Neurological conditions determining slowed or absent voluntary movement (hypokinesia) or excessive and involuntary movement (hyperkinesia)

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8
Q

List some Hypokinectic movement disorders

A

Slowed or absent voluntary movement
- Parkinsonism
- Parkinson’s disease
- Atypical parkinsonisms

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9
Q

List some Hyperkinectic movement disorders

A

Excessive and involuntary movements
- Tremor
- Dystomia, Chorea
- Tics
- Myoclonus

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10
Q

What is Parkinson’s disease characterised by?

A

Bradykinesia
- Progressive reduction of amplitude
- Progressive reduction of speed
- Lack of spontaneous movements
- Difficulty to execute internally generated movements > externally paced movements

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11
Q

Other than motor processing, what else does the basal ganglia control?

A

Non motor processing
- Basal ganglia are separated anatomically (and functionally) between different loops (motor, associative, limbic) and within loops

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12
Q

List the non motor functions of the basal ganglia

A
  • Attention
  • Explicit and implicit learning
  • Reward related behaviour
  • Habit formation
  • Time estimation
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13
Q

What basic functions does the basal ganglia controls?

A
  • Movement
  • Behaviour
  • Cognition
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14
Q

Where are the 3 basic loops into the basal ganglia connected?

A
  • Motor circuit: connected to the primary model right up to the supplementary grand motor area?.??
  • Associative circuit: Connected to the prefrontal areas
  • Limbic circuit: Connected to the limbic system
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15
Q

What is the importance of the basal ganglia loop?

A
  • The main output of the basal ganglia is inhibitory, so more activity = less movement
  • Two pathways through the basal ganglia exist, one which decreases output activity (increases movement) and one which increases output output activity (decreases movement)
  • Dopamine has different effects on these two pathways
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16
Q

Describe these two pathways

A

Called the rate model
- Has a stop pathway And a direct Go pathway

17
Q

Describe the indirect stop pathway in more detail

A

INPUT (STRATIUM - medium spiny neurons) -> OUTPUT (Gpi/SNr) via indirect stop pathway -> Thalamus/CTX
- Reduce movement

18
Q

Describe the direct go pathway in more detail

A

INPUT (STRATIUM - medium spiny neurons) -> OUTPUT (Gpi/SNr) via direct go pathway -> Thalamus/CTX via thalamic inhibition
- Increases movement by reducing thalamic inhibition

19
Q

What does a change in the firing rate determine?

A

Determines the degree of thalamic inhibition and therefore the amount of movement possible

20
Q

Describe the dopamine direct pathway

A
  • Dopamine activates the dotted pathway to the one receptor
  • The dotted pathway exert focus inhibition of the GPI
  • Which is the output component of the model loop of the basal ganglia
  • The reduced inhibition of GpI resulted in even increase of activity of the motor cortex because of reduced inhibition from the mouse
  • So focus inhibition of these GPI is the excitatory pathway or the motor loop
21
Q

Describe the indirect pathway

A
  • Mediated by the tourist sector
  • Exerts divergent excitation of the STN
  • The thalamic nucleus is an excitatory nucleus that produces glutamate that activate GPI to increase inhibitory action
  • More inhibition from the child almost to the cortex
22
Q

Describe the role of dopamine in the loop

A

Dopamine facilitates the direct pathway
- Dopamine inhibits the indirect pathway = Promotes movement
- Loss of dopamine will lead to increase of activity in GPi/SNr and leads to inhibition of thalamocortical pathways during the inhibition of motor function