Bill's lack of control over his motor movements is caused by low levels of the neurotransmitter dopamine.
What is Parkinson's disease?
Parkinson's or Parkinsonism is brought on by a decline in dopamine levels in the brain. The most noticeable Parkinson's disease signs and symptoms are when the nerve cells in the basal ganglia of the brain, which control movement, are damaged or killed.
The brain cells that produce dopamine slowly deteriorate because, without it, the cells that regulate movement cannot properly communicate with the muscles.
Therefore, low levels of the neurotransmitter dopamine are the root cause of Bill's inability to control his motor actions.
To learn more about Parkinson's disease, refer to the link:
https://brainly.com/question/13508690
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