Parkinson’s disease is a progressive neurological disorder that impacts movement and gradually worsens over time. This condition arises from changes within the brain, which relies on intricate networks of chemical messengers for its proper functioning. Understanding the specific chemical deficiency at the heart of Parkinson’s disease helps to clarify its effects on the body.
Understanding Brain Messengers
The brain’s vast communication network depends on specialized chemical messengers called neurotransmitters. These substances transmit signals between nerve cells, known as neurons, across tiny gaps called synapses. Neurotransmitters play a role in regulating many bodily functions, including movement, mood, and cognitive processes.
There are over a hundred different types of neurotransmitters, each with a specific role. They can either excite a target neuron to trigger a signal or inhibit it to prevent a signal, influencing how information flows throughout the brain.
Dopamine and Its Role
The primary neurotransmitter deficiency linked to the motor symptoms of Parkinson’s disease is dopamine. Dopamine is a chemical messenger involved in various brain functions, including movement, motivation, and reward. Balanced levels of dopamine are necessary for coordinating smooth, purposeful movements and preventing movement disorders.
Dopamine is mainly produced by specialized neurons located in the substantia nigra, a region deep within the midbrain. From the substantia nigra, dopamine travels along pathways to other brain areas, including the striatum, where it helps control motor function. Its influence also extends to aspects of executive functions, arousal, and reinforcement.
The Mechanism of Deficiency
In Parkinson’s disease, the nerve cells in the substantia nigra that produce dopamine begin to degenerate and die. This progressive loss of dopamine-producing neurons leads to a significant reduction in dopamine levels in the brain. By the time motor symptoms become noticeable, a substantial number of these dopamine-producing cells, often 60% to 80% or more, have already been lost or impaired.
This decrease in dopamine disrupts the delicate balance of chemical signals required for effective communication within the brain’s movement control circuits. The impaired signaling results in the characteristic motor symptoms of Parkinson’s disease, such as tremors, muscle rigidity, slowed movement (bradykinesia), and problems with balance and coordination.
Other Brain Chemical Connections
While dopamine deficiency is central to the motor symptoms of Parkinson’s disease, the condition is more complex and involves other brain chemicals. Other neurotransmitters, such as norepinephrine, serotonin, and acetylcholine, can also be affected as the disease progresses.
These additional chemical imbalances contribute to the wide array of non-motor symptoms experienced by individuals with Parkinson’s. Non-motor symptoms can include issues like depression, anxiety, sleep disturbances, fatigue, and cognitive changes. For instance, the loss of norepinephrine may explain symptoms such as fatigue and blood pressure changes, highlighting the widespread impact of Parkinson’s disease beyond just motor control.