Exam2Lec8BasalGanglia

Question 1

What is the function of the basal ganglia?

Answer 1

• Influence movement by regulating activity of upper motor neurons

Question 2

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

Answer 2

False

Question 3

List the motor componetns of the basal ganglia (4)

Answer 3

• 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

Question 4

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

Answer 4

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

Question 5

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

Answer 5

Modulate activity in anticipation and during movements

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

Question 6

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

Answer 6

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

Question 7

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

Answer 7

• Primary motor cortex
• Premotor cortex
• Supplementary motor cortex

Question 8

Where does the oculomotor loop originate in? (2)

Answer 8

• Frontal Eye Fields
• Supplementary Eye Fields

Question 9

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

Answer 9

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

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

Striatum

Question 13

What are the two parts of the Globus Pallidus?

Answer 13

• Internal Segment
• External Segment

Question 14

What is the Lenticular Nucleus?

Answer 14

The Globus pallidus and Putamen together

Appears as biconvex lens in 3D

Question 15

What are the parts of the Substantia nigra?

Answer 15

• Pars compacta
• Pars reticula

Question 16

What is contained in the Substantia nigra pars compacta?

Answer 16

Dopaminergic neurons

Question 17

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

Answer 17

Substantia nigra pars compacta

Question 18

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

Answer 18

Straitum

Question 19

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

Answer 19

Medium Spiny Neurons (MSN)

Question 20

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

Answer 20

• Globus pallidus
• Substantia nigra pars reticulata

Question 21

Where does the substantia nigra pars reticulata project into?

Answer 21

Superior colliculus

Influences visually guided behavior

Question 22

What are the two types of MSNs dopamine receptors?

Answer 22

• D1
• D2

Question 23

For D1 MSN list the:

• Neurotransmitter
• How dopamine is expressed
• Dendritic pattern
• “Excitability”

Answer 23

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

Question 24

For D2 MSN list the:

• Neurotransmitter
• How dopamine is expressed
• Dendritic pattern
• “Excitability”

Answer 24

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

Question 25

What are the OUTPUT pathways of the basal ganglia?

Answer 25

* Direct Pathway * Indirect Pathway

Question 26

What does the DIRECT pathway promote?

Answer 26

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

Question 27

# 1 of 5 Explain the steps of the DIRECT Pathway

Answer 27

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.

Question 28

D1 MSNs of the DIRECT pathway facilitates __________ movement

Answer 28

Wanted

Question 29

What does the INDIRECT pathway do?

Answer 29

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

Question 30

Explain the steps of INDIRECT pathway?

Answer 30

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.** 5. This **increases inhibition of the VA/VL complex** and **prevents Glutamate release** onto the frontal cortex. **Thus we supress movement.** 6. HOWEVER, when the **substantia nigra pars compacta** releases **Dopamine** there is **inhibition of D2 MSN** and this **pathway halts.**

Question 31

D2 MSNs of the INDIRECT pathway supressed __________ movement

Answer 31

Unwanted

Question 32

Cortisol excitation of the STN also ___________ movement

Answer 32

Suppress

Question 33

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

Answer 33

TRUE

Question 34

Explain how direct and indirect pathway cooperate

Answer 34

* Direct pathway:**Activation of intended** movement/motor program * Indirect pathway: **Suppression of extraneous or inappropriate** motor program

Question 35

How did "Optogentic" experiments so evidence for the two pathways?

Answer 35

* 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.

Question 36

How does Dopamine facilitates movement?

Answer 36

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

Question 37

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

Answer 37

cholinergic (ChAT) striatal interneurons

Question 38

How do Cholinergic interneurons affect the striatum?

Answer 38

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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

Inhibition via M2 muscarinic ACh receptors

Question 41

How does post-synaptic facilitation of D2 MSNs occur?

Answer 41

* Activation via M1 muscarinic ACh receptors * Receptors not found in D1 MSNs

Question 42

What action can be reflected in dopamine neuron activity? ## Footnote Low yield

Answer 42

Reward “value” of a salient stimulus

Question 43

Explain the Reward "value" of a salient stimuls caused by dopamine neuron activity? ## Footnote Low yield

Answer 43

* 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.

Question 44

What does dopamine reniforcement contribute to? ## Footnote Low yield

Answer 44

HABIT formation

Question 45

Explain Habit formation ## Footnote Low yield

Answer 45

* 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. ## Footnote Dopamine contributes to the ability to form a habit

Question 46

What is Parkinson's disease (PD)?

Answer 46

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

Question 47

List the main motor signs of Parkinson's Disease (PD)? | "T.R.A.P."

Answer 47

* **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.

Question 48

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

Answer 48

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

Question 49

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

Answer 49

Bradykinesia

Question 50

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

Answer 50

α-synuclein

Question 51

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

Answer 51

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

Question 52

# 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

Answer 52

Are inhibitory and release GABA

Question 53

# 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

Answer 53

Motor units | Measures muscle activity

Question 54

What do we use to prove D1 and D2?

Answer 54

Optogenetics by using channelrhodopsins

Question 55

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

Answer 55

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

Question 56

What is lost in parkinson's disease

Answer 56

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

Question 57

What type of motor disorder is parkinson?

Answer 57

hypokinetic

Question 58

What are serveral genes that have linked to PD?

Answer 58

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

Question 59

Meds for PD fall into 3 categories

Answer 59

* 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

Question 60

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

Answer 60

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

Question 61

The limbic loop plays a major role in what?

Answer 61

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

Question 62

signs of HD

Answer 62

* 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

Question 63

HD is what type of disorder?

Answer 63

autosomal dominant * CAG repeats Also hyperkinesia

Question 64

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

Answer 64

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

Question 65

Where are cells lost in HD?

Answer 65

Caudate and putamen->striatum