This subtitled 4-minute video shows the intricate mechanisms involved in the progression of Alzheimer's disease in the brain.
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The human brain is a remarkable organ. Complex chemical and electrical processes take place within our brains that allow us to talk, move, see, remember, feel emotions and make decisions. Within a normal healthy brain, billions of cells called neurons constantly communicate with each other. They receive messages from each other as the electric charges travel through the axon to the end of the neuron. Electric charges release chemical messengers called neurotransmitters. Transmitters move through microscopic gaps, or synapses, between neurons. They bind to the receptor sites in the dendrites of the next neuron. This cellular circuit allows communication within the brain. Healthy neurotransmission is important for the brain to function well. Alzheimer's disease interrupts this intricate interaction. By compromising the ability of neurons to communicate with each other, disease eventually destroys memory and thinking skills. Scientific research has revealed some of the brain changes that occur in Alzheimer's disease. Abnormal structures called beta-amyloid plaques and neurofibrillary tangles are classic biological traits of the disease. Plaques are formed when specific proteins in the cell membrane of the neuron are processed differently. Normally, an enzyme called alpha-secretase cleaves the amyloid precursor protein, or APP, releasing a fragment. A second enzyme, Gamma-secretase, also cuts APP in another place. It is believed that these released fragments benefit the neurons. In Alzheimer's disease, the first cut is most often done by another enzyme, Beta-secretase. That, combined with the cut made by Gamma-secretase, results in the release of short fragments of APP called Beta-Amyloid. When these fragments cluster, they become toxic and interfere with the function of neurons. As more fragments are added, these oligomers increase in size and become insoluble, eventually forming Beta-Amyloid plaques. Neurofibrillary tangles are made when a protein called tau is modified. In normal brain cells, tau stabilizes structures critical to the cell's internal transport system. Nutrients and other cellular charges are transported up and down the structures called microtubules to all parts of the neuron. In Alzheimer's disease, abnormal tau is separated from the microtubules, causing them to crumble. The filaments of this tau combine to form entanglements within the neuron, disabling the transport system and destroying the cell. Neurons in certain brain regions become disconnected and eventually die, causing memory loss. As these processes continue, the brain shrinks and loses its function. We now know a lot about the changes taking place in the brain with Alzheimer's disease, but there is still much to learn. What other changes are taking place in the aging of the brain and its cells and what influence do other diseases, genetics and lifestyle factors have on the risk of developing Alzheimer's disease such as brain and body age? Scientific research is helping to unravel the mystery of Alzheimer's and related brain disorders As we learn more, researchers are increasingly approaching the discovery of ways to treat and prevent ulcally this devastating and fatal disease
Video credits to Alzheimer Universal YouTube channel