The cause of Parkinson's disease is the death of brain cells that produce:

Explanation

Parkinson's disease is a neurodegenerative disorder that affects movement. It is caused by the death of brain cells in a region of the brain that produces dopamine, a neurotransmitter that helps to regulate movement and emotional responses. The death of these cells leads to a deficiency of dopamine in the brain, resulting in the characteristic symptoms of Parkinson's disease, such as involuntary tremors, diminished motor power, and rigidity, which causes difficulty with balance and coordination. While the exact cause of the death of these brain cells is not known, it is thought to be related to a combination of genetic and environmental factors, like head trauma.