A patient who is diagnosed with Parkinson's disease (PD) states, I can't tie my shoelaces anymore." The healthcare provider recognizes that this patient's problem is due to a deficiency in which of these neurotransmitters?

PD is a progressive neurodegenerative disease that impacts the motor system. Dopamine helps the brain control movement and coordination. Neurons in the brain slowly stop producing dopamine in patients who have PD, making it increasingly difficult to control muscles for movement, including fine motor movement needed to tie one's shoelaces.