What are plaques and tangles?
As mentioned before, an abnormal amount of senile plaques alongside neurofibrillary tangles are the primary markers for Alzheimer's disease. Both of the proteins involved, beta amyloid and tau, are involved in how the cell wall is developed by assisting the formation of microtubules.
Researchers aren't sure yet about how plaques and tangles develop, but they do have their ideas. The tangles, for example, may be from the body attempting to protect against further damage. What is known is that the nerve cells so entangled are dead and dying.
Both of these proteins damage and even kill nerve cells when they act abnormally. However, this abnormal activity can exist in the brain for a decade or more before Alzheimer's symptoms even show.