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Neurobiology II > Basal Ganglia (Exam 2) > Flashcards

Basal Ganglia (Exam 2) Flashcards

1
Q

What is the basal ganglia and what does it influence?

A
  • Collection of gray matter nuclei located deep within the white matter of the cerebral hemisphere
  • Influence the descending motor system without directly projecting to periphery
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2
Q

What are the main components of the Basal Ganglia?

A
  • Caudate Nucleus
  • Putamen
  • Globus Pallidus (Internal & External Sement)
  • Subthalamic Nucleus
  • Substantia nigra
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3
Q

What makes up the striatum?

A
  • Caudate nucleus
  • Putamen
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4
Q

What makes up the lentiform nucleus?

A

Putamen
Globus Pallidus (internal & external segment)

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5
Q

In the striatum what separates and connects the caudate nucleus & putamen?

A
  • Separated by internal capsule
  • Connected by cellular bridges
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6
Q

What is the subthalamic nucleus and what is it derived from?

A
  • Spindle or cigar shaped structures just under thalamus
  • Derived embryologically from midbrain
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7
Q

Substantia nigra pars reticulate is what part of the substatia nigra? what is it?

A
  • Ventral portion
  • Cells similar to globus pallidus
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8
Q

Substantia nigra pars compact is what part of the substantia nigra and what comes from there?

A
  • Dorsal portion
  • Dopamine producing neurons
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9
Q

What arteries supply blood to the basal ganglia?

A
  • Lenticulostriate (branches of MCA)
  • Anterior choroidal (branch of ICA)
  • Recurrent artery of Heubner (branch of ACA)
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10
Q

Describe the motor channel of the Basal Ganglia
Function?
Thalamic Relay Nuclei?
Cortical Targets of Output?

A

Function: General motor control

Thalamic Relay Nuclei: Ventral lateral nucleus & ventral anterior nucleus

Cortical Target of Output: Supplementary motor area, premotor cortex, primary motor cortex

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11
Q

Describe the Oculomotor channel of the Basal Ganglia
Function?
Thalamic Relay Nuclei?
Cortical Targets of Output?

A

Function: Regulation of eye movements

Thalamic Relay Nuclei: Ventral anterior nucleus & Mediodorsal nucleus

Cortical Targets of Outputs: Frontal eye fields, supplementary eye fields

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12
Q

Describe the prefrontal channel of the Basal Ganglia
Function?
Thalamic Relay Nuclei?
Cortical Targets of Output?

A

Function: Cognitive functions

Thalamic Relay Nuclei: Ventral anterior nucleus & mediodorsal nucleus

Cortical Target of Output: prefrontal cortex

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13
Q

Describe the limbic channel of the Basal Ganglia
Function?
Thalamic Relay Nuclei?
Cortical Targets of Output?

A

Function: Regulation of emotions & motivational drives

Thalamic Relay Nuclei: Mediodorsal nucleus & ventral anterior nucleus

Cortical Target of Outputs: Anterior cingulate gyrus, orbital frontal cortex

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14
Q

What are the 3 thalamic relay nuclei?

A
  • Ventral lateral nucleus
  • Ventral anterior nucleus
  • Mediodorsal nucleus
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15
Q

Inputs to the Basal Ganglia, what is the neurotransmitter coming from the area and is it excitatory or inhibitory?
- Cerebral Cortex
- Substantia Nigra pars compacta
- Intralaminar nuclei of thalamus

A
  • Cerebral Cortex: glutamate (excitatory)
  • Substantia Nigra pars compacts: Dopamine (excitatory/inhibitory)
  • Intralaminar nuclei of thalamus: Glutamate (excitatory)
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16
Q

What are the modulatory inputs from subcortical systems?

A
  • Acetylcholine
  • Serotonin
  • Noradrenalin
  • Histamine
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17
Q

What is the input nuclei to the Basal Ganglia?

A

Striatum

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18
Q

What are the output nuclei from the Basal Ganglia?

A
  • Globus pallidus internal segment (GPi) (motor control of body)
  • Substantia nigra pars reticulate (SNr) (Motor control of head & neck)
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19
Q

Describe the Direct pathway broadly

A
  • Input from cortex to striatum
  • Striatum connect directly to GPi/SNr
  • Output to thalamic nuclei
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20
Q

Within the Direct pathway what neurotransmitter does each area give off and it it inhibitory or excitatory?

A

Cortex: Glutamate (Excitatory)
Striatum: GABA & Substance P (Inhibitory)
GPi/SNr: GABA (inhibitory)
Thalamus: Glutamate (excitatory)

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21
Q

What does the direct pathway allow and how does it happen?

A
  • Allows movement to occur
  • Excitation of the basal ganglia by the cortex leads to increased excitation of the motor cortex by disinhibition of the thalamus
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22
Q

Describe broadly the Indirect Pathway

A
  • Input from cortex to striatum
  • Striatum connects indirectly to GPi/SNr by stopping at the globus pallidus external segment and then the sub thalamic nuclei
  • Output to thalamic nuclei
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23
Q

Within the indirect pathway what neurotransmitter does each area give off and is it inhibitory or excitatory?

A

Cortex: Glutamate (Excitatory)
Striatum: GABA & Enkephalin (Inhibitory)
GPe: GABA (inhibitory)
STN: Glutamate (excitatory)
GPi/SNr: GABA (inhibitory)

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24
Q

In regards to the indirect pathway, in the resting state what is tonically active?

A

Both output nuclei (GPi/SNr) & GPe

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25
Q

In regards to the indirect pathway what is the basal ganglia doing to the thalamus and what happens with excitation?

A
  • At rest basal ganglia is inhibiting the thalamus
  • With excitation of the indirect pathway by the cortex inhibitors outflow is increased
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26
Q

Overall what does the indirect pathway do ti movement?

A
  • Inhibits unwanted movements
27
Q

When is dopamine excitatory and when is it inhibitory?

A
  • Dopamine is excitatory when it bind to D1 receptors of the direct pathway
  • Dopamine is inhibitory when it binds to D2 receptors of the indirect pathway
28
Q

What effect does dopamine have on the direct pathway?

A
  • Dopamine increase activity of the direct pathway
  • Promotes movement
29
Q

What effect does dopamine have on the indirect pathway?

A
  • Dopamine inhibits the activity of the indirect pathway
  • It inhibits movement inhibition
  • Promotes movement
30
Q

Who is broadly categorized as having a movement disorder?

A

Patients with lesions or damage to the basal ganglia present with abnormal movements and movement patterns

31
Q

What is the presentation of those with a hyperkinetic movement disorder?

A
  • Excessive
  • Uncontrolled
  • Involuntary movement
32
Q

What is the presentation of those with a hypokinetic movement disorder?

A
  • Rigidity
  • Slowness
  • Difficulty initiating movements
33
Q

If a lesion is unilateral to the basal ganglia where would the movement disorder symptoms be?

A

Contralateral

34
Q

In addition to motor symptoms what else can disorder of the basal ganglia cause?

A

Dysfunction in control of eye movements, cognition & emotional regulation

35
Q

What is bradykinesia?

A

slow movement

36
Q

What is hypokinesia?

A

Small movement or decreased amount of movement

37
Q

What is akinesia?

A

Absence of movement

38
Q

What are bradykinesia, hypokinesia & akinesia caused by?

A
  • Increased inhibitory outflow from the basal ganglia to the thalamus
  • May result from lesions in several regions
  • Common symptoms associated with Parkinson’s disease
39
Q

Is rigidity velocity or directional dependent?

A

No

40
Q

What is lead pipe rigidity?

A

Continuous resistance through range

41
Q

What is cogwheel rigidity?

A

ratchet-like interruptions in tone felt throughout range

42
Q

what is dystonia?

A

Co-contraction of agonist & antagonist muscles resulting in abnormal distorting positions of limbs, trunk or face

43
Q

Describe dystonia

A
  • Tend to be slower & somewhat sustained
  • Generalized, unilateral or focal
  • Treated with anticholinergic medications or Botox
  • Occurs with many disorders of basal ganglia
  • Commonly seen with acute or long term use of dopaminergic antagonist
44
Q

What is athetosis?

A

Writhing, twisting movements of limbs, face & trunk

45
Q

What is chorea?

A
  • Nearly continuous involuntary movements of extremities, trunk, neck, face & respiratory muscles
  • Low amplitude (may conceal w/ voluntary movements)
  • Large amplitude (may disrupt voluntary movements)
46
Q

What is ballismus?

A

Larger amplitude movements of proximal limb movements with rotary or flinging quality

47
Q

What is a tremor?

A

Rhythmic or semi-rhythmic oscillating movements

48
Q

What is a resting tremor?

A
  • Most prominent when limbs are relaxed
  • Common with Parkinson’s disease
49
Q

What is Postural tremor?

A
  • Seen when holding limbs active but still
50
Q

What is intention tremor?

A

Occurs when patients attempts to move limb to a target

51
Q

What is Parkinson’s Disease?

A
  • Common idiopathic neurodegenerative disorder
  • Loss of dopaminergic neurons in substantia nigra pars compacta
52
Q

What are some common symptoms of Parkinson’s disease?

A
  • Resting tremor
  • Bradykinesia
  • Rigidity
  • Postural instability/ gait disturbance
53
Q

In Parkinson’s disease what impact would loss of dopamine have on the direct pathway?

A
  • Less excitation of D1 receptors
  • Less activation of direct pathway
  • Less disinhibition
  • Less Movement
54
Q

In Parkinson’s disease what impact would loss of dopamine have on the indirect pathway?

A
  • Less inhibition of D2 receptors
  • Less inhibition of the indirect pathway
  • More inhibitory outflow from BG to thalamus
  • Less movement
55
Q

Overall in Parkison individuals have less dopamine what impact does this have on movement?

A
  • Inhibitory outflow of Basal Ganglia to thalamus is unusually high in individuals with too little dopamine
  • Movement is less likely to occur
  • Hypokinetic Movement Disorder
56
Q

What are some red flags that would lead you to believe that it is not idiopathic Parkinsons?

A
  • More symmetrical
  • Rapidly progressing
  • Little response to dopamine
  • Multiple system atrophy
  • Progressive supra nuclear palsy
  • Dementia with Lewy bodies
  • Corticobasal degeneration
  • Wilson’s dises
  • Drug induce Parkinsonism
57
Q

What is Huntington’s Disease?

A
  • Autosomal dominant neurodegenerative condition
  • Progressive atrophy of striatum
    • Initially degeneration of enkephalin containing stratal neurons
    • Later degeneration of all striatal neurons
58
Q

What are clinical symptoms of Huntington’s disease?

A
  • Chromatic movement disorder
  • Abnormal eye movements
  • Dementia
  • Psychiatric & emotional disturbances
59
Q

How would degeneration of enkephalin- containing striatal neurons impact on the function & output of the basal ganglia?

A
  • Enkephalin containing neurons are specifically those with D2 receptors that function as part of INDIRECT pathway
  • Unable to inhibit GPe so it continues to inhibit the STN
  • STN is unable to excite the output nuclei to increase inhibition
  • Less inhibition of unwanted movement (HYPERkinetic movement disorder)
60
Q

How would degeneration of all striatal neurons impact on the function & output of the basal ganglia?

A
  • Indirect
    • Reduced inhibition of unwanted movement
  • Direct
    - Increased inhibition of movement
61
Q

Huntington’s disease is what movement in beginning and what movement disorder in end?

A

Beginning disease is hyperkinetic movement disorder
-Later stages more hypo kinetic

62
Q

Describe stereotactic neurosurgery

A
  • External reference system place on patient & CT or MRI performed
  • Allows computer calculation of exact brain region in relation to the external reference system
  • Therapeutic ablation of brain tissue in specific regions
  • Lesions at specific locations can be used to alter function of basal ganglia in individuals with movement disorders
  • Irreversible
63
Q

Describe Deep brain stimulation

A
  • Electrodes placed in deep brain structures
  • Stimulation causes a depolarization block
  • Reversible dysfunction of neurons at the tip of the electrode
  • Reversible and adjustable
64
Q

What locations are targeted during deep brain stimulation when treating Parkinson’s Disease?

A
  • Subthalamic nucleus
  • Globus pallidus (internal segment)

Neurobiology II (14 decks)

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