week 10 PD

Question 1

Q10. How does dopamine loss in the substantia nigra affect thalamic activity and motor cortex output?

Answer 1

Model Answer:
Dopamine loss leads to overactivation of the indirect pathway, causing increased inhibition of the thalamus by GPi/SNr. This reduces thalamic excitation of the motor cortex, leading to slowness and difficulty initiating movement.

Question 2

Q1. List and briefly describe three motor symptoms of Parkinson’s Disease.

Answer 2

Model Answer:

Bradykinesia: Slowness of movement, including reduced amplitude and velocity.

Resting tremor: Involuntary, rhythmic tremor seen when muscles are at rest.

Rigidity: Increased muscle tone causing stiffness, often seen in neck and limbs.

Question 3

Q2. What is festinating gait, and how does it relate to Parkinson’s Disease?

Answer 3

Model Answer:
Festinating gait is characterized by rapid, short steps and a forward-leaning posture, commonly seen in Parkinson’s patients. It results from impaired motor planning and postural instability due to basal ganglia dysfunction.

Question 4

Q3. Identify three non-motor symptoms of Parkinson’s Disease.

Answer 4

Model Answer:

Sleep disturbances: Insomnia or REM sleep behavior disorder.

Mood disorders: Anxiety, depression.

Autonomic dysfunction: Constipation, urinary incontinence, orthostatic hypotension.

Question 5

🧠 Section 2: Pathogenesis and Neural Circuits
Q4. What is the primary neural change in Parkinson’s Disease?

Answer 5

Model Answer:
Progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta, leading to decreased dopamine signaling in the nigrostriatal pathway.

Question 6

Q5. Describe the role of Lewy bodies in Parkinson’s Disease.

Answer 6

Model Answer:
Lewy bodies are intracellular aggregates composed mainly of α-synuclein, found in surviving dopaminergic neurons. They are a pathological hallmark of the disease and reflect ongoing neurodegeneration.

Question 7

Q6. Explain the difference between the direct and indirect pathways in the basal ganglia and how they are affected in Parkinson’s Disease.

Answer 7

Model Answer:

Direct pathway (via D1 receptors): Facilitates movement.

Indirect pathway (via D2 receptors): Inhibits competing movements.
In Parkinson’s Disease, dopamine loss understimulates the direct and overstimulates the indirect pathway, leading to reduced movement initiation.

Question 8

🧠 Section 3: Treatments
Q7. Name two pharmacological treatments for Parkinson’s Disease and explain how they work.

Answer 8

Model Answer:

Levodopa: A dopamine precursor that crosses the blood-brain barrier and is converted to dopamine.

MAO-B inhibitors: Block the enzyme that breaks down dopamine, increasing its availability in the brain.

Question 9

Q8. What is Deep Brain Stimulation (DBS), and which brain areas are commonly targeted?

Answer 9

Model Answer:
DBS involves implanting electrodes into brain regions such as the subthalamic nucleus (STN) or globus pallidus internus (GPi). Electrical stimulation helps restore motor function by modulating abnormal neural activity.

Question 10

Q9. What are some limitations of pharmacological treatment for Parkinson’s Disease?

Answer 10

Model Answer:

Reduced efficacy over time (tolerance).

“On-off” phenomenon: Fluctuations in motor performance.

Dyskinesia: Involuntary, erratic movements due to chronic dopaminergic therapy.

Question 11

Flashcard 1
Q: What is the function of the direct pathway in the basal ganglia?

Answer 11

A: It facilitates voluntary movement by reducing inhibitory output from the GPi/SNr to the thalamus, allowing the motor cortex to activate.

Question 12

Flashcard 2
Q: Which dopamine receptor subtype is involved in the direct pathway?

Answer 12

A: D1 dopamine receptors.

Question 13

Flashcard 3
Q: What is the function of the indirect pathway in the basal ganglia?

Answer 13

A: It suppresses unwanted movement by increasing inhibitory output from the GPi/SNr to the thalamus, reducing motor cortex activation.

Question 14

Flashcard 4
Q: Which dopamine receptor subtype is involved in the indirect pathway?

Answer 14

A: D2 dopamine receptors.

Question 15

Flashcard 5
Q: What is the role of dopamine in the direct and indirect pathways?

Answer 15

A: Dopamine stimulates the direct pathway (via D1) and inhibits the indirect pathway (via D2), promoting movement.

Question 16

Flashcard 6
Q: What happens to the direct pathway in Parkinson’s Disease?

Answer 16

A: It becomes underactive due to loss of dopamine → reduced movement facilitation.

Question 17

Flashcard 7
Q: What happens to the indirect pathway in Parkinson’s Disease?

Answer 17

A: It becomes overactive due to loss of dopamine inhibition → excessive movement suppression.

Question 18

Flashcard 8
Q: What is the net effect of dopamine loss in Parkinson’s Disease on movement?

Answer 18

A: Increased inhibition of the thalamus → decreased motor cortex activity → bradykinesia and rigidity.

Question 19

Flashcard 9
Q: Which basal ganglia nuclei are involved in both direct and indirect pathways?

Answer 19

A: Striatum, GPi, GPe, STN, SNr, SNc.

Question 20

Flashcard 10
Q: How does Deep Brain Stimulation (DBS) help in Parkinson’s Disease?

Answer 20

A: It targets STN or GPi to reduce excessive inhibition on the thalamus, improving motor cortex output and movement.