Parkinson's Disease
The symptoms of Parkinson's Disease are tremors, muscle rigidity, slowed movements, and/or the inability to move and impaired balance and speech. Tremors are characterized by the uncontrolled shaking of extremities, specifically the hands. Muscle rigidity is the tightening of muscles. The disease is caused by the loss of the dopamine-producing cells within the substantia nigra of the midbrain. The lack of dopamine disables the substantia nigra-basal ganglion connection necessary for controlled movement.
There are two substantia nigra in the brain. One is on the right side and one is on the left side deep in the midbrain. The cells of the substantia nigra produce and use the neurotransmitter dopamine to send signals that coordinate movement. Because of an unknown factor harming the substantia nigra, cells in this region that produce dopamine continue to degenerate and die. The death of these dopamine-generating cells causes a disruption in the process of relaying messages to other important motor regions, such as basal ganglia. The effected substantia nigra slowly reduces the supply of dopamine to the region resulting in symptoms. These severe symptoms do not usually appear until 80% of dopamine-producing cells of the substantia nigra are lost. No cure has been discovered, although the drug L-dopa can elevate dopamine levels in the brain and reduce symptoms for some people suffering from Parkinson's disease.
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