Final answer:
Parkinson's disease is associated with a deficiency of the neurotransmitter dopamine, leading to various motor and non-motor symptoms, and treatments aim to enhance dopamine levels.
Step-by-step explanation:
Parkinson's disease is caused by a lack of dopamine, a neurotransmitter essential for regulating movement and coordination. This neurodegenerative disease leads to the death of neurons in the substantia nigra, a part of the brain that produces dopamine.
The loss of these dopaminergic neurons results in symptoms such as tremors, bradykinesia, muscular rigidity, and balance and posture problems. Treatments focus on increasing dopamine levels or simulating its effects to improve these symptoms.