Final answer:
Parkinson's disease is linked to the degeneration of dopamine neurons in the substantia nigra, resulting in motor symptoms and cognitive decline. Serotonergic, noradrenergic, cholinergic, and glutamatergic systems are also disrupted in PD.
Step-by-step explanation:
Parkinson's disease (PD) is linked to the degeneration of dopamine neurons in the substantia nigra. Loss of these neurons leads to a reduction of dopaminergic innervation, resulting in primary motor symptoms such as tremor, bradykinesia, muscular rigidity, and postural instability. In addition to motor symptoms, PD can also cause cognitive decline, depression, and anxiety. Studies suggest disruption in serotonergic, noradrenergic, cholinergic, and glutamatergic systems in PD patients.