Alzheimer's Disease

Alzheimer's disease leads to nerve cell death. In an Alzheimer's brain: The cortex shrivels up damaging areas involved in thinking, planning and remembering. Shrinkage is especially severe in the hippocampus. Ventricles (fluid filled spaces within the brain) grow larger. Alzheimer's tissue has a lot fewer synapses and nerve cells than a healthy brain. Plaques, abnormal clusters of protein fragments, build up between nerve cells. Dead and dying nerve cells contain tangles, which are made up of twisted strands of another protein. Scientsts are not absolutely sure what causes cell death and tissue loss in an Alzheimer's brain, but plaques and tangles are the main suspect. Plaques form when protein pieces called beta-amyloid clump together. Beta-amyloid comes from a larger protein found in the fatty membrane surrounding nerve cells. Bet-amyloid is chemically 'sticky' and gradually builds up into plaques The most damaging form of beta-amyloid may be groups of a few pieces rather than plaques themselves. The small clumps may block the cell-to-cell signaling at synapses. In healthy areas of the brain: The transport system is organised in orderly parallel strands somewhat like railroad tracks. A protein called Tau helps the tacks to stay straight. In areas where tangles are forming: Tau collapses into twisted strands called tangles. The tracks can no longer stay straight. They fall apart and disintegrate. Nutrients and other essential supplies can no longer move through the cell, which eventually dies. Plaques and tangles tend to spread through the cortex in a predictable pattern as Alzheimer's disease progresses. The rate of progression varies greatly. People with Alzheimer's live an average of 8 years, but some people may survive for up to 20 years.

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