I am currently working on a project related to Parkinson's disease, and I learnt a lot about how PD develops. In this context, I ran into a question that I could not answer myself. As PD results in a degeneration of dopaminergic brain cell, it causes a deficit of the neurotransmitter dopamine. The symptoms that can be observed and that are typical for PD are mostly affecting the motor capabilities of a patient.
My question is: How can one explain the tremor in the hands of a patient for example?
I assumed that if there is a neurotransmitter missing, it would result in the affected body parts to become numb and immobile. However, for PD, the patient heavily struggles to perform voluntary movement, but involuntary movements seem to be present quite a lot.
Thank you for your help!