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Neurology in Health & Disease > L16 Basal Ganglia > Flashcards

L16 Basal Ganglia Flashcards

1
Q

Components of the Basal Ganglia (4 Neuroanatomical Structures)

A
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2
Q

Where is the Nucelus Accumbens Located?

A

Ventral Part of the Caudate Nucleus of Striatum

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3
Q

Three Key Elements of Basal Ganglia Circuit?

A
  1. Input from other brain regions into Basal Ganglia (Striatum)
  2. Circuits within Basal Ganglia
  • Striatum => Globus Pallisus (Striatopallidal Tract)
  • Striatum => Substantia Nigra (Striatonigral Tract)
  1. Output from Basal Ganglia
  • Internal Pallidal Segment (GPi)
  • Substantia Nigra Pars Reticulata (SNr)
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4
Q

_________________ is the receivers of input to the Basal Ganglia. It receives _______________input from multiple regions:

  • _____________________
  • _____________________
  • _____________________
  • ____________________
A

STRIATUM is the receivers of input to the Basal Ganglia. It receives excitatory input from multiple regions:

  • CEREBRAL CORTEX
  • HIPPOCAMPUS
  • AMYDGALA
  • THALAMUS
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5
Q

Signals into the STRIATUM (Basal Ganglia) are relayed to the _________________and ________________by _______________ neurons

A

Signals into the STRIATUM (Basal Ganglia) are relayed to the Globus Pallidus and Substantia Nigra by INHIBITORY (GABAergic) neurons

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6
Q

Components of the Substantia Nigra:

  • Projections?
  • Neuron Type?
A

Pars Compacta (SNc)

  • Contains neuromelanin (Black Color)
  • DOPAMINERGIC Neuron Project to STRIATUM (Nigrostrital)

Pars Reticulata (SNr)

  • GABAergic Neurons project to THALAMUS (Nigrothalamic) and BRAINSTEM
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7
Q

Dopamine Receptors

  • How do they elicit their various functions?
  • What type of receptor are they?
  • How are different types essential to Basal Ganglia Function?
A

Dopamine Receptors:

□ Single transmitter => multiple receptors => multiple outcomes

□ All are G-Protein Coupled Receptors (NOT Ion Channels, no action potential on their own but alter excitability)

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8
Q

Outputs From the Basal Ganglia:

  • Names?
  • Type of Neurons?
  • Targets?
A
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9
Q

_______________________(___________):

  • Activates adenylyl cyclase => INCREASED cAMP
  • EXCITATORY
A

D1-Like Receptors (D1 & D5):

  • Activates adenylyl cyclase => INCREASED cAMP
  • EXCITATORY
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10
Q

_______________________(___________):

  • Inhibits adenylyl cyclase => INCREASED cAMP
  • INHIBITORY
A

D2-Like Receptors (D2, D3, D4):

  • Inhibits adenylyl cyclase => INCREASED cAMP
  • INHIBITORY
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11
Q

Circuit of the Basal Ganglia

§ ___________ is the main receiver of INPUT into the Basal Ganglia

§ ____________________ and _______________________=>OUTPUT

§ _____________________ regulates direct and indirect pathways through release of Dopamine => effects on striatal outputs depend on post-synaptic receptor:

  • D1 (_________)=> _________________
  • D2(______) => _________________
A

Circuit of the Basal Ganglia

§ Striatum is the main receiver of INPUT into the Basal Ganglia

§ Globus Pallidus Internal Pallidal Segment (Gpi) and Sunstantia Nigra Pars Reticulata (SNr) =>OUTPUT

§ Pars Compacta (SNc) regulates direct and indirect pathways through release of Dopamine => effects on striatal outputs depend on post-synaptic receptor:

  • D1(D1 & D5) => ACTIVATION
  • D2 (D2, D3, D4) => INHIBITION
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12
Q

Functions of Direct vs. Indirect Basal Ganglia Thalamocortical Pathway?

What Regulates the Balance?

A

Direct: Facilitates Movement

Indirect: Inhibits Movement

Balance between DIRECT and INDIRECT pathways regulated by Dopamine from Pars Compacta (SNc): SNc does not generate the signal but rather permits a signal to pass through the circuit

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13
Q

Direct Basal Ganglia Thalamocortical Pathway

  • Striatum (D__)=> __________________ => ______________
  • Pathway _________ by Dopamine from Pars Compacta (SNc)
  • ___________Thalamus => __________________
A

Direct Basal Ganglia Thalamocortical Pathway

  • Striatum (D1) => Globus Pallidus Internal Segment (Gpi) => Thalamus
  • Pathway ACTIVATED by Dopamine from Pars Compacta (SNc)
  • REMOVES INHIBITION from Thalamus => Movement
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14
Q

Indirect Basal Ganglia Thalamocortical Pathway

  • Striatum (D__) => _______________=> __________________ => ____________________=> Thalamus
  • Pathway ____________ by Dopamine from Pars Compacta (SNc)
  • ___________Thalamus => ___________________
A

Indirect Basal Ganglia Thalamocortical Pathway

  • Striatum (D2) => Globus Pallidus External Segment (GPe)=> Subthalamic Nucleus (STN)=> Globus Pallidus Internal Segment (Gpi) => Thalamus
  • Pathway INHIBITED by Dopamine from Pars Compacta (SNc)
  • INHIBITS Thalamus => No Movement
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15
Q

Which part of the Basal Ganglia is involved in cognitive control of Motor Activity (Intention, Initiation, Selection)?

A

Caudate Nucleus

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16
Q

Which part of the Basal Ganglia is involved in the execution of learned motor programs?

17
Q

Functions of the Basal Ganglia?

18
Q

What do lesions to the Spinal Cord Result in?

A

Paralysis below site of lesion

19
Q

What do lesions to the cortex result in?

A

Weakness of Muscle Contraction, Periodic Paralysis

20
Q

What do lesions to the cerebellum result n?

A

Deficits in motor EXECUTION, but not initiation

21
Q

What do lesions to the Basal Ganglia Result in?

A

Interference with STRATEGIC PLANNING and INITIATION OF MOVEMENT

22
Q

Characteristics of Hemiballismus:

  • Clinical Signs
  • Cause
A

Hemiballismus (Basal Ganglia Disfunction):

  • Rare and severe movement disorder characterized by involuntary Balistic Firing movement of limbs (CONTRALATERAL to injury)
  • Results from damage to Subthaalaic Nuceli => Decreased activity of the indirect pathway =>decreased suppression of undesired movements
23
Q

Characteristics of Huntington’s Disease?

  • Clinical Signs
  • Cause
A

Huntington’s Disease (Basal Ganglia Dysfunction):

  • Underlying Striatal damage due to mutation in the huntingtin gene (htt)
  • Characterised by Chorea (Random, jerky, uncontrollable movements)
  • Aditional cognitive deficits
24
Q

Characteristics of Parkinson’s Disease?

  • Clinical Signs
  • Cause
A

Parkinson’s Disease (Basal Ganglia Dysfunction):

  • Underlying Substantia Nigra damage
  • Characterised by Tremor, Rigidity, Slow Movement
  • Later cognitive problems/dementia
  • Preceded by autonomic dysfunction
25
Q

Cerebellar Ataxia vs. Parkinsonian Gait?

  • Walk?
  • Postural Sway?
  • Stride Length?
A

Ataxic Gait:

□ Unsteady, uncoordinated, irregular walk, feet thrown out, wide base- Results from inappropriate timing of movement (Dysmetria)

□ INCREASED postural sway

□ Disproportionate increase in stride length with increasing velocity

Parkinsonian Gait:

□ Slow, short steps, with tremors and rigidity

□ DECREASED postural sway

□ LINEAR increase in stride length with increasing velocity

Neurology in Health & Disease (18 decks)

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