Question 35
NECO_MODEL_QUESTIONS_VOL1
•
2021
•
BIOLOGY
•
objective
In Parkinson's disease the loss of dopaminergic neurons in the substantia nigra disrupts the balance between the direct and indirect basal‑ganglia pathways. Explain how this imbalance leads to a resting tremor and why administration of levodopa alleviates the tremor.
Answer Options
A.
The loss of dopamine primarily affects the cerebellar circuits, causing increased thalamic output and a resting tremor; levodopa acts by directly stimulating muscle fibers to reduce tremor.
Correct Answer
B.
Dopamine loss weakens the direct pathway and disinhibits the indirect pathway, causing excessive thalamic inhibition and a resting tremor; levodopa restores dopamine, re‑balancing the pathways and reducing the tremor.
C.
Dopamine loss strengthens the direct pathway and inhibits the indirect pathway, leading to excessive thalamic excitation and a resting tremor; levodopa further suppresses dopamine, worsening the tremor.
D.
Dopamine deficiency reduces activity in the indirect pathway while leaving the direct pathway unchanged, resulting in reduced thalamic inhibition and a resting tremor; levodopa alleviates tremor by blocking GABA receptors.
Correct Answer
B
Correct Option:
Dopamine loss weakens the direct pathway and disinhibits the indirect pathway, causing excessive thalamic inhibition and a resting tremor; levodopa restores dopamine, re‑balancing the pathways and reducing the tremor.
About This Question
This is
Neco Model Questions Vol1
2021
Biology
Question 35.
It is one of the
objective
questions from the
2021
Neco Model Questions Vol1
Biology
examination.
Difficulty level:
Medium
.