Understanding the Nature of Parkinson’s Disease: A Neurological Movement Disorder

Parkinson’s disease is one of those conditions that quietly reshapes a person’s entire life – not all at once, but gradually, movement by movement. It is a progressive neurological disorder that primarily affects how the body moves, and understanding its nature requires looking deep inside the brain, at the level of individual nerve cells and the chemical signals they rely on. For anyone working in education, caregiving, or disability support, grasping how and why this condition develops is essential to offering meaningful, informed support.

What is Parkinson’s disease? 🔗

Parkinson’s disease is formally defined under India’s Rights of Persons with Disabilities (RPwD) Act, 2016 as a progressive disease of the nervous system marked by tremor, muscular rigidity, and slow, imprecise movement, primarily affecting middle-aged and elderly people. It is associated with degeneration of the basal ganglia of the brain and a deficiency of the neurotransmitter dopamine. This legal recognition is significant – it places Parkinson’s disease among the 21 categories of disability recognized under the RPwD Act, 2016, broadening access to support and benefits for those living with the condition.

At its core, Parkinson’s is a movement disorder – but that description barely captures its full impact. The condition worsens over time and affects not just physical movement but, in many cases, cognitive functioning and emotional wellbeing as well. Research indicates that Parkinson’s disease has affected approximately 0.58 million people in India alone, and this number is expected to rise in the coming decades.

The role of the central nervous system 🔗

To understand Parkinson’s disease, we first need to understand the system it disrupts: the Central Nervous System (CNS). The CNS consists of the brain and the spinal cord. Together, they serve as the command centre for the entire body – receiving information from the environment, processing it, and sending out instructions that control everything from heartbeat to handwriting.

As MedlinePlus explains, the nervous system is made up of billions of neurons that communicate with each other constantly. When the brain initiates an impulse – say, to lift an arm – that impulse travels through a network of nerve pathways, passing through key brain regions before reaching the muscles. One of the most critical of these regions for movement control is the basal ganglia.

The basal ganglia: the brain’s movement coordinator 🔗

The basal ganglia are a group of structures located deep within the brain, beneath the cortex. According to the MSD Manual, the basal ganglia help initiate and smooth out voluntary muscle movements, suppress unwanted movements, and coordinate changes in posture. When the brain sends a movement signal, it passes through the basal ganglia, which fine-tune that signal before it reaches the muscles.

Within the basal ganglia lies a specific region called the substantia nigra – a Latin term meaning “black substance,” named for the dark pigment produced by the dopamine precursor found there. The substantia nigra is where dopamine, the neurotransmitter most critical to movement control, is produced.

How neurons and neurotransmitters work 🔗

Neurons are the fundamental building blocks of the nervous system. Each neuron has three key parts: dendrites, which receive incoming signals; the cell body (soma), which processes those signals; and the axon, which carries the outgoing signal to the next cell. However, neurons don’t actually touch each other. Between any two neurons lies a tiny gap called a synapse.

For a signal to cross this gap, it must be converted from an electrical impulse into a chemical message. This chemical signal is called a neurotransmitter. The sending neuron releases neurotransmitter molecules into the synapse; those molecules then bind to receptors on the receiving neuron and trigger the next signal in the chain. This process – happening billions of times per second across the nervous system – is what allows the brain to coordinate every thought, sensation, and movement.

As Cleveland Clinic describes, neurotransmitters carry chemical signals from one neuron to the next target cell, which can be another nerve cell, a muscle cell, or a gland. The body simply cannot function without them.

Dopamine: the movement messenger 🔗

Among the many neurotransmitters in the brain, dopamine holds a particularly important role in movement. It is produced primarily in the substantia nigra and acts as a key modulator within the basal ganglia circuit. According to research published on NCBI, dopamine plays an essential role in several brain functions, including learning, motor control, reward, and executive functions.

In terms of movement specifically, Mayfield Brain & Spine explains that dopamine-producing nerve cells in the substantia nigra are responsible for relaying messages that plan and control body movement. When dopamine is released into the basal ganglia, it helps balance two competing pathways – one that promotes movement (the direct pathway) and one that suppresses it (the indirect pathway). This balance is what allows us to move smoothly and purposefully.

The impact of dopamine deficiency in Parkinson’s disease 🔗

In Parkinson’s disease, the dopamine-producing neurons in the substantia nigra begin to degenerate and die. The reason this happens is not yet fully understood, but the consequences are well-documented. According to current research, by the time the motor symptoms of Parkinson’s become noticeable, between 50 and 80 percent of all dopaminergic neurons in the substantia nigra may have already degenerated.

As dopamine levels fall, the carefully maintained balance between the direct and indirect pathways in the basal ganglia is disrupted. Research published in the journal Neuron explains that when dopamine is lost, the direct (movement-promoting) pathway becomes underactive while the indirect (movement-suppressing) pathway becomes overactive. The net effect is excessive inhibition of the brain regions that initiate movement – meaning the brain essentially has too many brakes and not enough acceleration.

This neurological disruption produces the hallmark symptoms of Parkinson’s disease:

• Tremor at rest – involuntary shaking, typically in the hands, that decreases with purposeful movement
• Bradykinesia – slowness of movement, affecting everything from walking pace to facial expression
• Muscular rigidity – stiffness in the limbs and trunk that makes movement effortful
• Postural instability – balance problems that increase the risk of falls

As Mayfield Clinic notes, when approximately 80 percent of dopamine is lost, these symptoms of Parkinson’s disease – including tremor, slowness of movement, stiffness, and balance problems – become clinically apparent.

Why the disruption spreads beyond movement 🔗

While the basal ganglia have traditionally been seen as the central region affected by Parkinson’s, research published in npj Parkinson’s Disease proposes that the disorder should be understood as a dysfunction of the broader basal ganglia-cortex-cerebellum system. This wider perspective helps explain why Parkinson’s disease can also affect cognition, mood, and autonomic functions like digestion and sleep – well beyond simple movement impairment.

Additionally, the death of dopamine-producing cells is often accompanied by the formation of abnormal protein clumps called Lewy bodies – misfolded proteins (primarily alpha-synuclein) that accumulate inside neurons. These Lewy bodies are found not just in the substantia nigra, but also in the cortex, the amygdala, and structures linked to heart rate and digestion, which helps explain the range of symptoms that people with Parkinson’s experience.

A condition that progresses over time 🔗

The word “progressive” in the definition of Parkinson’s disease is important. The condition does not appear overnight, nor does it remain static. Neurons continue to degenerate over time, and symptoms typically worsen gradually. Research from India notes that Parkinson’s disease primarily affects those over the age of 60, though younger-onset cases do occur. As more people are diagnosed at younger ages, the importance of early recognition and long-term support continues to grow.

For educators, disability support professionals, and families, understanding this progressive nature means recognizing that the level of support a person with Parkinson’s needs today may be very different from what they will need a year from now. Flexibility, awareness, and ongoing adaptation are essential.

What do you think? Considering that Parkinson’s disease progressively disrupts the brain’s own communication system, how might this understanding change the way educators and support professionals design learning environments or daily routines for individuals living with the condition? And given that dopamine deficiency affects not just movement but also mood and cognition, how should disability support training be updated to reflect this broader neurological impact?

References

1. https://www.disabilityrightsindia.com/2017/04/what-21-disabilities-covered-in-rights.html
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC6436405/
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC10637607/
4. https://medlineplus.gov/ency/anatomyvideos/000089.htm
5. https://www.msdmanuals.com/home/brain-spinal-cord-and-nerve-disorders/movement-disorders/parkinson-disease-pd
6. https://www.neurolab360.com/blog/basalgangliaandpd
7. https://my.clevelandclinic.org/health/articles/22513-neurotransmitters
8. https://www.ncbi.nlm.nih.gov/books/NBK539894/
9. https://mayfieldclinic.com/pe-pd.htm
10. https://en.wikipedia.org/wiki/Parkinson%27s_disease
11. https://www.sciencedirect.com/science/article/pii/S0896627319302119
12. https://www.nature.com/articles/npjparkd201625