People with Parkinson’s disease often experience tremors at rest because of a specific disruption in the brain’s control of movement caused by the loss of dopamine-producing nerve cells. These nerve cells are located in an area called the substantia nigra, which is part of a larger brain system known as the basal ganglia. The basal ganglia play a crucial role in regulating smooth and coordinated muscle movements. When dopamine levels drop due to neuron degeneration, this balance is disturbed, leading to involuntary shaking or tremors that typically occur when muscles are relaxed and not actively being used.
To understand why these tremors happen specifically at rest, it helps to know how normal movement control works. In healthy individuals, dopamine acts like a chemical messenger that helps fine-tune signals between different parts of the brain involved in starting and stopping movements smoothly. It suppresses unwanted muscle activity when you’re not moving so your limbs stay steady. In Parkinson’s disease, because dopamine is deficient, this suppression weakens — resulting in rhythmic oscillations or shaking even when muscles should be still.
This resting tremor usually appears as a slow back-and-forth motion most commonly seen in hands or fingers but can also affect other body parts like legs or chin. It tends to diminish during voluntary movement because active muscle use temporarily overrides the abnormal signaling causing the tremor.
The exact mechanism behind these resting tremors involves complex changes within neural circuits:
– The loss of dopamine disrupts communication between neurons in the basal ganglia.
– This causes abnormal firing patterns and increased synchronization among certain groups of neurons.
– These irregular signals then lead to involuntary contractions alternating with relaxation cycles—felt externally as trembling.
Additionally, other neurotransmitters besides dopamine may contribute by altering excitability within motor pathways.
Parkinsonian resting tremor differs from other types such as essential tremor (which occurs mainly during action) because it reflects underlying neurodegeneration rather than just an overactive nervous system response.
Besides trembling at rest, people with Parkinson’s also experience symptoms like muscle stiffness (rigidity), slowness of movement (bradykinesia), and impaired balance—all linked to similar disruptions caused by reduced dopamine availability affecting motor control networks.
In summary, **resting tremors** arise primarily due to **dopamine deficiency** disrupting normal inhibitory signals within motor circuits controlled by the basal ganglia; this leads to involuntary rhythmic shaking when muscles are relaxed but improves with intentional movement engaging those muscles actively.