Scientists believe that for most people, Alzheimer's disease results from a combination of genetic, lifestyle, and environmental factors that affect the brain over time. Alzheimer's disease is caused by specific genetic changes that virtually guarantee that a person will develop the disease. The causal effect of this disease is still unknown, with the fingers pointing to plaques and tangles in the brain. Although the causes of Alzheimer's disease are not yet fully understood, its effects on the brain are clear. Alzheimer's disease damages and kills brain cells. A brain with Alzheimer's disease has far fewer cells and far fewer connections between surviving cells than a healthy brain. As more and more brain cells die, Alzheimer's disease causes enormous brain shrinkage. When doctors examined the brain tissue of a patient with Alzheimer's disease under a microscope, they found two types of abnormalities believed to be the cause of the disease. One of these abnormalities is plaque clumping, a protein called beta-amyloid that damages and destroys brain cells. In patients with Alzheimer's disease, the plaques created interfere with cell-to-cell communication. The other abnormality observed involves tangles in the brain. Brain cells depend on an internal support and transportation system to transport nutrients and other essential materials along their long extensions. This system requires the normal structure and function of a protein called tau. In a patient with Alzheimer's disease, the tau protein strands twist into abnormal tangles inside brain cells, causing the transport system to fail. (Alzheimer's Association) (National Institutes of Health, 2012) There are three stages to Alzheimer's disease and one should be aware of the important signs and symptoms. For example, one must be aware of middle of paper ... Additionally, patients with Alzheimer's disease have difficulty understanding visual images and spatial relationships. In terms of perception, they may walk past a mirror and think someone else is in the room with them. They often have difficulty recognizing their own reflection. (Alzheimer's Association) (Mayo Clinic) Works Cited Alzheimer's Association. (nd). Alzheimer’s Association. Retrieved April 21, 2014, from Alzheimer's Association: http://www.alz.org/alzheimers_disease_what_is_alzheimers.aspMayo Clinic. (nd). Mayo Clinic. Retrieved April 21, 2014, from Alzheimer's Disease: http://www.mayoclinic.org/diseases-conditions/alzheimers-disease/basics/definition/con-20023871National Institutes of Health. (2012, September). Alzheimer's disease fact sheet. Retrieved from National Institute on Aging: http://www.nia.nih.gov/alzheimers/publication/alzheimers-disease-fact-sheet