Biology

Parkinson's disease is a neurodegenerative disorder that affects movement.

In Parkinson's, there is a progressive loss of dopamine-producing neurons in the substantia nigra of the brain. The lack of dopamine leads to motor symptoms such as tremors (shaking), muscle rigidity (stiffness), bradykinesia (slowness of movement), and problems with balance and coordination.

The other options are incorrect:

Alzheimer's is primarily a neurodegenerative disorder that affects memory, thinking, and behavior. While it may eventually lead to some motor symptoms as the disease progresses, its main characteristics are cognitive decline such as memory loss, confusion, and problems with language and judgment.