What is the result of the degeneration of dopamine in Parkinson's disease?

In Parkinson's disease, the degeneration of dopamine-producing neurons in the brain, particularly in an area known as the substantia nigra, leads to a significant functional deficit. Dopamine is a crucial neurotransmitter that helps to regulate movement and coordination. As the levels of dopamine decrease, individuals experience symptoms such as weak and slow movements—referred to as bradykinesia—and rigidity, which is characterized by increased muscle tone and stiffness. This combination of symptoms reflects the motor control issues that occur due to the lack of adequate dopamine signaling, ultimately resulting in impaired voluntary movements.

The nature of these symptoms underscores how critical dopamine is for smooth, coordinated motion. The muscle stiffness and reduced motion can make it difficult for individuals to initiate movements, leading to the characteristic shuffling gait often seen in those with Parkinson's disease. Understanding this degeneration helps clarify why the answer focuses on the effects of dopamine loss and its direct impact on physical movement and muscle function.