Parkinson's disease leads to the degeneration of which type of cells?

Parkinson's disease primarily affects the brain cells, particularly the neurons in a specific area of the brain known as the substantia nigra. These neurons are responsible for producing dopamine, a neurotransmitter that plays a critical role in coordinating movement. As these brain cells degenerate and die, the levels of dopamine decrease, leading to the characteristic motor symptoms of Parkinson's disease, such as tremors, rigidity, and bradykinesia (slowness of movement).

While nerve cells could be considered a broad category that includes brain cells, the specificity of the question targets the degeneration linked to Parkinson's disease. Muscle cells and blood cells are not directly impacted by the disease's pathology, focusing the degeneration specifically on brain cells in the context of managing movement and coordination. This specificity underscores why the correct answer is brain cells, as they are pivotal in the disease's manifestation and symptoms.