The Effects on your Health of Alzheimer's

Alzheimer's disease leads to nerve cell death and tissue loss throughout the brain. Over time, the brain shrinks dramatically, affecting nearly all its functions.

In the Alzheimer's brain:

• The cortex shrivels up, damaging areas involved in thinking, planning and remembering.

• Shrinkage is especially severe in the hippocampus, an area of the cortex that plays a key role in formation of new memories.

• Ventricles (fluid-filled spaces within the brain) grow larger.

Scientists can also see the terrible effects of Alzheimer's disease when they look at brain tissue under the microscope:

• Alzheimer's tissue has many fewer nerve cells and synapses 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.

Scientists are not absolutely sure what causes cell death and tissue loss in the Alzheimer's brain, but plaques and tangles are prime suspects.

Plaques form when protein pieces called beta-amyloid (BAY-tuh AM-uh-loyd) clump together. Beta-amyloid comes from a larger protein found in the fatty membrane surrounding nerve cells.

Beta-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 the plaques themselves. The small clumps may block cell-to-cell signaling at synapses. They may also activate immune system cells that trigger inflammation and devour disabled cells.