Parkinson’s results from destruction of dopamine-producing neurons in part of the brain (substantia nigra).
A lack of these neurons causes decreased excitation of the motor part of the brain. This results in the classic signs of a resting tremor
(“pill-rolling”), slowness of movement (shuffling steps), rigidity (resistance to being moved), and postural instability (balance issues).
Answer assisted by Erin Brennan, Medical Student