Final answer:
Parkinson's disease is a neurodegenerative disorder caused by the loss of dopamine-producing neurons in the substantia nigra, leading to symptoms like tremors and slowed movement.
Step-by-step explanation:
Parkinson's disease is a neurodegenerative disease that presents characteristic symptoms such as tremors, slowed movement, speech changes, balance and posture problems, and rigid muscles. It is caused by the degeneration of neurons in the substantia nigra, a region of the midbrain. These neurons are responsible for producing and releasing the neurotransmitter dopamine, which plays a critical role in coordinating movement. As these dopaminergic neurons degenerate, the resulting dopamine deficiency leads to the various motor and sometimes cognitive symptoms associated with the disease. Treatment for Parkinson's disease often includes medication aimed at increasing dopamine levels, such as the provision of L-DOPA, which is a precursor to dopamine that can cross the blood-brain barrier.