Parkinson's symptoms usually don't appear until 70-80% of the substantia nigra neurons have died.

Question

Quizplus · Accepted Answer

Parkinson's disease is a progressive disorder of the nervous system that affects movement. The substantia nigra is a specific area of the brain that produces a chemical called dopamine which is essential for normal movement. Studies suggest that Parkinson's symptoms usually don't appear until 70-80% of the dopamine-producing neurons in the substantia nigra have died. Therefore, option A is correct.

Parkinson's Symptoms Usually Don't Appear Until 70-80% of the Substantia