& x20;What causes the resting tremors in Parkinson's disease? - INI-CET EXAM -2026

INI-CET EXAM -2026

Medical & Surgical Nursing

Hard

Appeared in: INI-CET EXAM -2026

Explanation

In Parkinson's disease, the loss of dopaminergic neurons in the substantia nigra leads to a disruption of the basal ganglia circuits.
This disruption causes the indirect pathway to become overactive, leading to hyperactivity of the subthalamic nucleus (STN).
The hyperactive STN provides excessive excitatory input to the globus pallidus interna (GPi).
This over-excitation of the GPi is a key step in the pathophysiology.
The overactive GPi then excessively inhibits the thalamus, which in turn reduces excitatory signals to the motor cortex, resulting in motor symptoms like tremors.

Option A: The globus pallidus externa (GPe) is actually more inhibited by the striatum in Parkinson's disease, not less inhibited. This is a key step in the overactivation of the indirect pathway.
Option B: While the direct pathway's inhibitory input to the GPi is reduced, the dominant effect is the powerful excitation from the subthalamic nucleus (STN). The net result is GPi overactivity, not just a loss of its inhibition.
Option D: The globus pallidus externa (GPe) is inhibited by the striatum in Parkinson's disease, not excited. This increased inhibition of the GPe is what disinhibits the subthalamic nucleus.

Clinical Relevance

Nursing practice connection: Knowing Pathophysiology of Parkinson's Disease helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding this pathophysiology is crucial for nurses to grasp why medications like Levodopa (a dopamine precursor) and surgical treatments like Deep Brain Stimulation (DBS) of the STN or GPi are used. These treatments aim to restore balance to this disrupted circuit.
The classic motor symptoms of Parkinson's—Tremor (at rest), Rigidity, Akinesia/Bradykinesia, and Postural instability (TRAP)—are all direct consequences of the thalamic inhibition caused by the overactive GPi.
What if? If a patient had a lesion in the subthalamic nucleus (STN) instead of dopamine loss, they would likely develop hemiballismus (a hyperkinetic, or excessive movement, disorder), not parkinsonism. This is because a damaged STN cannot excite the GPi, leading to less inhibition of the thalamus and thus uncontrolled movements.

How to Approach the Question

First, identify the core concept: the pathophysiology of Parkinson's disease and its effect on the basal ganglia.
Recall the two main pathways of the basal ganglia: the direct (facilitates movement) and indirect (inhibits movement) pathways.
Remember that dopamine from the substantia nigra is depleted in Parkinson's. Dopamine normally excites the direct pathway and inhibits the indirect pathway.
Analyze the consequence of dopamine loss: The indirect pathway becomes disinhibited (overactive).
Trace the steps of the overactive indirect pathway: Striatum inhibits GPe -> GPe stops inhibiting STN -> STN becomes hyperactive -> STN excites GPi.
Conclude that the final common step leading to thalamic inhibition is the excitation of the globus pallidus interna (GPi).

Concept Tested & Keywords

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