Seniors and Elderly Health

The Changing Brain of Alzheimers

To date no exact cause has been attributed to Alzheimer's Disease, however research has shown that the brains of Alzheimer's patients have an abundance of two abnormal structures - beta amyloid plaques and neurofibrillary tangles.

The human brain is a complex, not very well understood, but extremely important organ.

Groups of neurons in the brain have special jobs. For example, some are involved with thinking, learning, and memory. Others are responsible for receiving sensory information. Still others communicate with muscles, stimulating them into action.

Several processes all have to work smoothly together for neurons to survive and stay healthy.

These processes are:

1. Communication between neurons and cells a process involving electrical nerve impulses and chemical neurotransmitters.

2. Turning chemicals and nutrients into energy to keep the neurons working

3. Repair, in an adult, when neurons die because of disease or injury, they are not usually replaced. If cell cleanup and repair slows down or stops for any reason, the nerve cell cannot function well. Eventually, it dies.

Alzheimer's disease disrupts each of the three processes that keep neurons healthy: communication, metabolism, and repair. This disruption causes certain nerve cells in the brain to stop working, lose connections with other nerve cells, and finally, die. The destruction and death of nerve cells causes the memory failure, personality changes, problems in carrying out daily activities, and other features of Alzheimer's Disease.

To date no exact cause has been attributed to Alzheimer's Disease, however research has shown that the brains of Alzheimer's patients have an abundance of two abnormal structures - beta amyloid plaques and neurofibrillary tangles. Although many older people also develop some plaques and tangles, the brains of Alzheimer's patients have them to a much greater extent.

Amyloid Plaques - are made of a protein fragment called beta-amyloid. These fragments clump together and are mixed with other molecules, neurons, and non-nerve cells. In Alzheimer's Disease, plaques develop in the hippocampus, a structure deep in the brain that helps to encode memories, and in areas of the cerebral cortex that are used in thinking and making decisions. We still don't know whether beta-amyloid plaques themselves cause Alzheimer's or whether they are a by-product of the disease process.

Neurofibrillary Tangles - Healthy neurons have an internal support structure partly made up of structures called microtubules. These microtubules act like tracks, guiding nutrients and molecules along the neuron. A special kind of protein, tau, makes the microtubules stable. In Alzheimer's, tau is changed chemically, it begins to pair with other threads of tau and they become tangled up together. When this happens, the microtubules disintegrate, collapsing the neuron's transport system, resulting in malfunctions in communication between neurons and later in the death of the cells

At this stage researchers are unsure if amyloid plaques and neurofibrillary tangles are harmful or if they are merely side effects of the disease process that damages neurons and leads to the symptoms of Alzheimer's.

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