Alzheimer’s disease is a progressive condition that damages the brain’s ability to function. Common symptoms of AD include forgetfulness, problems remembering things, confusion about time, and inability to recognize loved ones.
AD is not a simple matter of “not trying hard enough” or “not paying attention”. Alzheimer’s disease is caused by physical changes in the structure of the brain. Researchers are still trying to determine whether these physical changes are the cause or the result of Alzheimer’s disease.
Amyloid plaques
The brain is made up tens of billions of nerve cells called neurons. These neurons communicate by sending electrical impulses across connections known as synapses. Normally, signals pass freely from one neuron to the next.
Researchers estimate that one neuron can be connected and passing signals to as many as 7,000 other neurons at any time.
In AD, fragments of the protein beta-amyloid cluster together to form amyloid plaques that build up between neurons. This prevents the signals from passing from one neuron to another which hinders the brain’s ability to think and form new memories.
Scientists are not sure if beta-amyloid plaques cause AD, or a result of the disease.
Tau tangles
A rich supply of blood is critical to support the function of cells in the brain. Between 20 and 25 percent of the blood in the human body travels to the brain to deliver a fifth of the body’s total oxygen and fuel.
In a healthy brain, nutrients and oxygen travel down organized paths known as microtubules. These are often compared to railroad tracks because they run parallel to each other and help guide nutrients from the center to the extremities of each cell.
A protein called tau is believed to help support the structure of these microtubules.
In AD, changes to the tau protein cause it to clump and cause tangles. These tangles block the microtubules and disrupt the transport system that moves nutrients and oxygen through the nerve cells.
Brain cells that do not receive enough oxygen are more likely to disintegrate and die.
Shrinking brain
Amyloid plaques and tau tangles both interfere with the ability of neurons to connect and pass signals to other neurons. When a neuron loses connections, it stops functioning and eventually dies.
As brain cells die, liquid-filled spaces inside the brain expand as the brain itself shrinks.
Typically, this brain shrinkage is most severe in areas of the brain that help form new memories.
Researchers believe the physical changes in the brain in connection with Alzheimer’s may begin as long as 20 years before any symptoms appear.
Age is the best-known risk factor for developing Alzheimer’s. Over 90 percent of patients diagnosed with AD are over the age of 60.
If you have questions or concerns about Alzheimer’s disease, talk to your health care provider.
Sources:
National Institute on Aging. A Primer on Alzheimer’s Disease and the Brain. Web. November 17, 2014.
http://www.nia.nih.gov/alzheimers/publication/2011-2012-alzheimers-disea...
Bright Focus Foundation. How the Brain and Nerve Cells Change During Alzheimer’s Disease. Web. November 17, 2014.
http://www.brightfocus.org/alzheimers/about/understanding/brain-nerve-ce...
Alzheimer’s Association. Braintour: Supply lines. Web. November 17, 2014.
http://www.alz.org/braintour/blood_vessels.asp
Healthline. What Does Alzheimer’s Do to the Brain? Treacy Colbert. Web. November 17, 2014.
http://www.healthline.com/health-slideshow/alzheimers-and-brain#1
Reviewed November 18, 2014
by Michele Blacksberg RN
Edited by Jody Smith