Parkinson's disease is most closely associated with destruction of the myelin sheath
stimulation of action potentials decreases in levels of dopamine
an increase in the number of synapses
reduced availability of acetylcholine

The Second one

Explanation:

Parkinson's disease is caused by a loss of nerve cells in the part of the brain called the substantia nigra. Nerve cells in this part of the brain are responsible for producing a chemical called dopamine.

between the two muscle layers is the myenteric or auerbach's plexus, which controls peristalsis. in the colon, the muscularis externa is much thicker because the feces are large and heavy, requiring more force to push along. the stomach has a third layer of muscularis externa: the inner oblique layer.