Final answer:
Parkinson's disease is a neurodegenerative disorder that causes the loss of dopaminergic neurons in the substantia nigra, resulting in symptoms like tremors and slowed movement. It also affects cognitive function, leading to memory loss and depression. The exact cause of the disease is not fully understood.
Step-by-step explanation:
Parkinson's disease is a neurodegenerative disorder that causes the loss of dopaminergic neurons in the substantia nigra. As a result, patients experience symptoms such as tremors, slowed movement, speech changes, balance and posture problems, and rigid muscles. The disease also affects cognitive function, leading to memory loss, depression, and eventually dementia. The exact cause of Parkinson's is still not fully understood, but research suggests that genetic and environmental factors, as well as excitotoxicity, may play a role.