Why is there extreme slowness of movement in Parkinson's disease?

Extreme slowness of movement in Parkinson's disease, known as bradykinesia, is primarily due to the degeneration of dopamine-producing neurons in the substantia nigra region of the brain. Dopamine is crucial for coordinating smooth and controlled movements, and its deficiency disrupts the communication between the brain and muscles. This results in difficulty initiating and performing voluntary movements, leading to the characteristic slowness observed in individuals with Parkinson's. Additionally, the disease affects other neural pathways involved in motor control, further contributing to movement challenges.