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Neurosciences > Exam2Lec8BasalGanglia > Flashcards

Exam2Lec8BasalGanglia Flashcards

1
Q

What is the function of the basal ganglia?

A
  • Influence movement by regulating activity of upper motor neurons
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2
Q

True or False. The Basal Ganglia projects directly on lower motor neurons

A

False

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3
Q

List the motor componetns of the basal ganglia (4)

A
  • Straitum
    1. Caudate
    2. Putamen
  • Globus padillus (Internal and external portions)
  • Subthalamic nucleus
  • Substantia nigra (located in the brain stem)
    1. Pars compacta
    2. Pars retculata
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4
Q

What do motor components of the basal ganglia and midbrain create?

A

A sub-cortical loop that links much of the cerebral cortex with the primary motor and premotor cortices and the brainstem

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5
Q

What is the function of neurons in the subcorticol loop created by the components of the basal ganglia?

A

Modulate activity in anticipation and during movements

Their effects on upper motor neurons are required for normal performance of voluntary movements

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6
Q

What occurs if the basal ganglia or its associated structures are compromised?

A

The motor system cannot switch smoothly between commands that initiate movement and those that terminate movement

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7
Q

What cortex (es) does the motor loop originate in? (3)

A
  • Primary motor cortex
  • Premotor cortex
  • Supplementary motor cortex
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8
Q

Where does the oculomotor loop originate in? (2)

A
  • Frontal Eye Fields
  • Supplementary Eye Fields
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9
Q

What is the basic pathway (w/out specific structures) for the motor and oculomotor loops)

A

Primary Cortex→Cortical Input→Straitum→Pallidum→Thalamus→Primary Cortex

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10
Q

True or False: The Ventral lateral and ventral anterior nuclei (VA/VL complex) is part of the Basal Ganglia

A

FALSE
It is a relay station (thalamus) for the motor loop which sends signals form our principal nuclei back to the cerebral cortex

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11
Q

What are the two parts of the Stratium and what seperates them?

A
  • Caudate
  • Putamen
  • Seperated by the Internal Capsule (myelinated axons leaving and entering the cerebrum)
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12
Q

What region of the basal ganglia has the highest risk of stroke?

A

Striatum

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13
Q

What are the two parts of the Globus Pallidus?

A
  • Internal Segment
  • External Segment
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14
Q

What is the Lenticular Nucleus?

A

The Globus pallidus and Putamen together

Appears as biconvex lens in 3D

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15
Q

What are the parts of the Substantia nigra?

A
  • Pars compacta
  • Pars reticula
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16
Q

What is contained in the Substantia nigra pars compacta?

A

Dopaminergic neurons

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17
Q

All of the following receive output signals EXCEPT:

A. Globus pallidus internal segment
B. Substantia nigra pars reticulata
C. Globus pallidus external segment
D. Substantia nigra pars compacta

A

Substantia nigra pars compacta

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18
Q

What is the major recipient of INPUTs to the basal ganglia from the cerebral cortex and midbrain?

A

Straitum

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19
Q

What is the name of the neurons responsilbe for sending output signals from the striatum?

A

Medium Spiny Neurons (MSN)

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20
Q

What location(s) does the MSNs project from the striatum?

A
  • Globus pallidus
  • Substantia nigra pars reticulata
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21
Q

Where does the substantia nigra pars reticulata project into?

A

Superior colliculus

Influences visually guided behavior

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22
Q

What are the two types of MSNs dopamine receptors?

A
  • D1
  • D2
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23
Q

For D1 MSN list the:

  • Neurotransmitter
  • How dopamine is expressed
  • Dendritic pattern
  • “Excitability”
A
  • Neurotransmitter: GABA
  • How dopamine is expressed: Excites
  • Dendritic pattern: More dendrites
  • “Excitability”: Less
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24
Q

For D2 MSN list the:

  • Neurotransmitter
  • How dopamine is expressed
  • Dendritic pattern
  • “Excitability”
A
  • Neurotransmitter: GABA
  • How dopamine is expressed: Inhibits
  • Dendritic pattern: Fewer dendrites
  • “Excitability”: More
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25
Q

What are the OUTPUT pathways of the basal ganglia?

A
  • Direct Pathway
  • Indirect Pathway
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26
Q

What does the DIRECT pathway promote?

A

Promotes movement via disinhibition of the VA/VL thalamus making inputs to cortex more effective

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27
Q

1 of 5

Explain the steps of the DIRECT Pathway

A
  1. Glutamate from the cerebral cortex activates D1 MSN in the striatum.
  2. This triggers the release of GABA onto the globus palidus, internal segment which is tonically active at rest.
  3. GABA from the striatum will thus STOP the release of GABA from the globus palidus, internal segment onto the VA/VL and decrease its inhibition.
  4. Decreased inhibition of the VA/VL complex of the thalamus triggers the release of Glutamate onto the frontal cortex which facilitates movement.
  5. When Dopamine is being released from the substantia nigra pars compacta there will be an excitatory effect on D1 MSN. This will enhance D1 MSN activity and continue to facilitate the direct pathway and movement.
28
Q

D1 MSNs of the DIRECT pathway facilitates __________ movement

29
Q

What does the INDIRECT pathway do?

A

Makes direct pathway less effective – VA/VL complex inhibited more.

30
Q

Explain the steps of INDIRECT pathway?

A
  1. Glutamate from the cerebral cortex activates D2 MSN in the striatum.
  2. This triggers the release of GABA onto the globus pallidus, external segment which is tonically active at rest.
    3.GABA from the striatum will thus STOP the release of GABA from the globus pallidus, external segment onto the subthalamic nucleus AND the globus pallidus, internal segment.
    4.Disinhibition of both the subthalamic nucleus and the globus pallidus, internal segment thus increases tonic release of GABA onto the VA/VL complex of the thalamus.
  3. This increases inhibition of the VA/VL complex and prevents Glutamate release onto the frontal cortex. Thus we supress movement.
  4. HOWEVER, when the substantia nigra pars compacta releases Dopamine there is inhibition of D2 MSN and this pathway halts.
31
Q

D2 MSNs of the INDIRECT pathway supressed __________ movement

32
Q

Cortisol excitation of the STN also ___________ movement

33
Q

True or False. The release of Dopamine (regardless of direct or indirect pathway) will lead to movement.

34
Q

Explain how direct and indirect pathway cooperate

A
  • Direct pathway:Activation of intended movement/motor program
  • Indirect pathway: Suppression of extraneous or inappropriate motor program
35
Q

How did “Optogentic” experiments so evidence for the two pathways?

A
  • Activation of direct pathway MSNs reduced freezing and increased locomotion.
  • Bilateral excitation of indirect-pathway MSNs elicited a “Parkinsonian-like” state by
    increased freezing, bradykinesia, and decreased locomotor initiations.
36
Q

How does Dopamine facilitates movement?

A

By enhancing the direct pathway & moderating (limiting) the indirect pathway via the distinct actions on the two types of MSNs

37
Q

What else is found in the striatum that a role in modulatinf behavior?

A

cholinergic (ChAT) striatal interneurons

38
Q

How do Cholinergic interneurons affect the striatum?

A

Salient stimuli” can trigger the release of Acetylcholine at the striatum

39
Q

What does the release of ACh by cholinergic interneurons lead to?

A
  • Pre-synaptic inhibition of excitatory cortical inputs onto D1 & D2 MSNs
  • Post-synaptic facilitation of the indirect pathway via activation of D2 MSNs
40
Q

How does pre-synaptic inhibiton of D1 and D2 MSNs occur?

A

Inhibition via M2 muscarinic ACh receptors

41
Q

How does post-synaptic facilitation of D2 MSNs occur?

A
  • Activation via M1 muscarinic ACh receptors
  • Receptors not found in D1 MSNs
42
Q

What action can be reflected in dopamine neuron activity?

Low yield

A

Reward “value” of a salient stimulus

43
Q

Explain the Reward “value” of a salient stimuls caused by dopamine neuron activity?

Low yield

A
  • Sensory stimulus serving as a reward elicits a pause response in cholinergic interneurons, in the striatum
  • Simultaneously, burst discharges in dopamine (DA) neurons in the substantia nigra pars compacta
  • The pause in acetylcholine release amplifies the dopamine signal.
44
Q

What does dopamine reniforcement contribute to?

Low yield

A

HABIT formation

45
Q

Explain Habit formation

Low yield

A
  • Habits (mannerisms, customs, and rituals) are largely learned.
  • Habitual behaviors occur repeatedly & can become remarkably fixed.
    Fully acquired habits are
    performed almost automatically - allowing attention to be focused elsewhere.
    Habits tend to involve an ordered, structured action sequence that is prone to being elicited by a particular context
    or stimulus.

Dopamine contributes to the ability to form a habit

46
Q

What is Parkinson’s disease (PD)?

A

A chronic progressive neurodegenerative movement disorder caused by degeneration (lost) of dopaminergic inputs to the striatum.

47
Q

List the main motor signs of Parkinson’s Disease (PD)?

“T.R.A.P.”

A
  • Tremor, or trembling in hands, arms, legs, jaw, or head
  • Rigidity, or stiffness of the limbs and trunk
  • Bradykinesia, or slowness of movement [akinesia - absence, poverty, or loss of control of voluntary muscle
    movements]
  • Postural instability or impaired balance.
48
Q

Which of the following correctly describes the effects of glutamatergic signaling (from the cerebral cortex) on D1 MSN’s?

A. ↑ inhibition of Globus pallidus internal segment; ↓ inhibition of VA/VL complex
B. ↓ inhibition of Globus pallidus external segment; ↑ inhibition of VA/VL complex
C. ↓ inhibition of Globus pallidus internal segment; ↑ inhibition of VA/VL complex
D. ↑ inhibition of Globus pallidus external segment; ↓ inhibition of VA/VL complex

A

↑ inhibition of Globus pallidus internal segment; ↓ inhibition of VA/VL complex

49
Q

Scientists at the Morsani College of Medicine are studying a rare congenital defect which leads to excess production and release of acetylcholine within the basal ganglia. Which of the following symptoms would a patient suffering from this condition likely experience?

A. Athetosis
B. Motor impulsivity
C. Bradykinesia
D. Chorea

A

Bradykinesia

50
Q

Parkinson’s Disease is characterized by the loss of dopaminergic neuronal cells in the substantia nigra and abnormal accumulation of Lewy bodies within the brain. What protein is responsible for Lewy body aggregation?

A. Parkin
B. α-synuclein
C. DJ-1
D. PINK1

A

α-synuclein

51
Q

Huntington’s disease is a rare, congenital disorder that causes the progressive degeneration of structures responsible for voluntary movement. Which of the following correctly describes the pathology of this condition?

A. ↑ inhibition of Subthalamic nucleus; ↑ inhibition of VA/VL complex
B. ↓ inhibition of Globus pallidus external segment; ↑ inhibition of VA/VL complex
C. ↑ inhibition of Globus pallidus internal segment; ↓ inhibition of VA/VL complex
D. ↓ inhibition of Subthalamic nucleus; ↓ inhibition of VA/VL complex

A

↑ inhibition of Globus pallidus internal segment; ↓ inhibition of VA/VL complex

52
Q

Dr. Yao’s sample question

The medium spiny neurons of the striatum have which of the following characteristics?

A. Are excitatory and release dopamine
B. Are excitatory and release glutamate
C. Are inhibitory and release GABA
D. Are inhibitory and release dopamine

A

Are inhibitory and release GABA

53
Q

Dr. Yao’s in class sample question

The EMG (electromyography) directly measures of the electrical activity of:

A. Only alpha motor neurons
B. Only gamma motor neurons
C. Motor units
D. Muscle spindel afferents

A

Motor units

Measures muscle activity

54
Q

What do we use to prove D1 and D2?

A

Optogenetics by using channelrhodopsins

55
Q

What does the release of ACh by cholinergic interneurons lead to?

A
  • Pre-synaptic inhibition of excitatory cortical inputs onto D1 & D2 MSNs
  • Post-synaptic facilitation of the indirect pathway via activation of D2 MSNs
56
Q

What is lost in parkinson’s disease

A

dopaminergic inputs to the striatum are lost. This deficit changes the output of the direct and indirect pathways and impair motor control

57
Q

What type of motor disorder is parkinson?

A

hypokinetic

58
Q

What are serveral genes that have linked to PD?

A

a-synucelin: led to discovery that lewy bodies from people with the sporadic form of PD contained clumps of the a-synuelin protein with the B pleated sheet pattern-amyloids

Parkin: translated into a protein that normally helps cells break down and recycle proteins

DJ-1: notmally helps regulat gene activity and protect cells from oxidative stress

PINK1: codes for a protein active in mitochondria. Mutations in this gene appears to increase susceptibility to cellular stress

59
Q

Meds for PD fall into 3 categories

A
  • in/directly to increase level of dop. in brain (LEVODOPA)
  • affter other NT in body to ease some of the symtopms of the disease (ANTICHOLINERGIC DRUGS) to decrease tremors, and muscle stiffness
  • Control the non motor symptoms: depression is treated with antidepressants
60
Q

The associative circuit contributes to cognitive tasks referred to as _ _

A

executive functions:
* organizing behavorial responses
* rule infernece
* conflict management
* verbal skills in problem sloving
* working memory

61
Q

The limbic loop plays a major role in what?

A

socially appropriate behavior in response to social cues
* Emotional lability
* Irritability
* failure to response to social cues

62
Q

signs of HD

A
  • Uncontrolled mvt in fingers, feet, face, or trunk
  • Chora (uncontrolled, irregular, rapid, jerky mvts) often occuring with athelosis (writhing, involuntary mvts of flexion, ext, of muscles)
  • mild clumsiness ot problems with balance
63
Q

HD is what type of disorder?

A

autosomal dominant
* CAG repeats

Also hyperkinesia

64
Q

HD is triggered by the mutant protein. Both _ and _ mechanisms are involved

A

gain of function (of the mutant protein) and loss of function (of the normal protein)

65
Q

Where are cells lost in HD?

A

Caudate and putamen->striatum

Neurosciences (28 decks)

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