Biology 202
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Alzheimer’s Disease

Alicia Ebbitt

I am extremely fascinated by the I-function and memory and how these concepts relate to each other and how they relate to the study of neurobiology. I am quite curious about the role that the memory plays in the concept of an I-function. I believe that memory and the I-function go hand in hand. A large part of a person’s identity is the memories they have of past experiences, so I feel that memory is a very large part of the I-function. Originally, for my second neurobiology paper, I wanted to study memory loss and determine what areas of the brain are believed to be involved in memory loss and what sort of damage to the nervous system causes memory loss. I was unable to find alot of specific information on memory loss, because it is such a broad topic, so I have decided instead to do my study on Alzheimer’s Disease. One of the symptoms of Alzheimer’s is a terrible memory loss. Through my study of Alzheimer’s, I have come to an understanding of what areas in the brain are affected by this disease and some of the indirect causes of the symptoms of Alzheimer’s, such as memory loss.

Alzheimer’s Disease is a progressive neurodegenerative disease. It attacks the nervous system and results in severe dementia which is characterized by impaired memory, thinking, and behavior. Dementia is a decline in intellectual functioning that in its later phases can seriously interfere with a person’s ability to perform daily activities. The likelihood that a person may develop Alzheimer’s increases considerably with age. The percentage of people over 85 with Alzheimer’s Disease is 47.2%.

Alzheimer’s develops gradually in an individual. It is characterized by symptoms such as memory loss and loss of intellectual functioning. This memory loss begins with a short term memory loss. What is quite interesting about the memory loss due to Alzheimer’s Disease is that certain things and daily activities may be forgotten, while others are not. This aspect of the disease raised many questions in my head. Why are only certain things forgotten? Is this a random process, or could it be that certain abilities are forgotten because they were inherited and genetic information is damaged? Or could it be that the I-function is damaged and learned things and abilities instead are forgotten? Unfortunately, the information I collected on Alzheimer’s did not deal with these questions. However I have speculated these questions and feel they are worth further investigation. A person with Alzheimer’s may have difficulty with language and communication and may make poor or decreased judgment as well. Those suffering from Alzheimer’s may also exhibit apathy, and a loss of spontaneity and interest in an active life, and a loss of initiative. (3. and 2.) Victims of Alzheimer’s may also experience confusion and disorientation in place and time, changes in behavior or personality, problems with abstract thinking, anxiety, and depression. Eventually Alzheimer’s patients become totally unable to care for themselves.(Alz. Assoc...) After detection of Alzheimer’s, a person may live anywhere from three to 20 or more years. However, Alzheimer’s leaves its patients less resistant to infections and other illnesses. These are often the ultimate cause of death.

There are may other diseases that cause dementia and are quite similar to Alzheimer’s. Often, these other diseases can be stopped, reversed, or even cured. For this reason, early detection and diagnosis of these diseases is quite important.

Diagnosis of Alzheimer’s Disease can be determined by microscopic brain tissue changes. These include the presence of fiber tangles within nerve cells(neurofibrillary tangles), which are malfunctions within neurons, and clusters of degenerating nerve endings(neuritic plaques), which are chemical deposits consisting of degenerating neurons combined with a form of protein called beta amyloid. These plaques and tangles are found in the areas of the brain that play an important role in memory and intellectual abilities. Plaques are made in part from protein molecules(amyloid precursor protein(APP)) that normally are essential components of the brain. Plaques are produced when an enzyme prematurely snips(APP) apart at a specific place and then leaves the fragments(beta amyloid) in the brain tissue. Here they come together in abnormal deposits. It has not yet been determined how neurofibrillary tangles are formed. Alzheimer’s Disease is also characterized by a reduced production of certain brain chemicals or neurotransmitters, especially acetylcholine. These chemicals are absolutely necessary for successful communication through neurons.

Alzheimer’s Disease begins in the entorhinal cortex of the brain and proceeds to the hippocampus(3). The hippocampus is a structure deep in the brain, involved in memory storage.(2.) As Alzheimer’s attacks the hippocampus, its neurons degenerate, causing short term memory loss. Then, Alzheimer’s spreads to other regions, particularly the cerebral cortex. The cerebral cortex is an outer area of the brain that plays an important role in functions such as language and reason. Here, Alzheimer’s causes a loss in language and communication abilities. Alzheimer’s attacks these regions of the brain causing the neurons to degenerate. As a result, these neurons lose their synapses with other neurons, causing them to be unable to communicate with other neurons and pass on information. Some of these neurons even die. (3)

At this point int time, no direct causes fro Alzheimer’s are entirely known. Currently, an intesive, investigative search for these causes is under way among scientist all over the world. It is suspected that genes, abnormal protein deposits in the brain, and other risk, and environmental factors play an important role in the cause of Alzheimer’s Disease. All of these suspicions however are only speculations and unfortunetely there is no absolute proof as to the specific cause of Alzheimer’s.

Biochemical Changes in Growth Trophic Factors may contridute to the causation of Alzheimer’s Disease. This theory is that naturally occuring substances in the brain may affect the nervous system and contribute to the dysfunction or death or brain cells in a patient with Alzheimer’s. Nerve Growth Factor is one of these naturally occuring subsatnces. It helps to maintain the functioning of brain cells. In many Alzheimer’s patients a severe rise or decline in this sustance is seen. From this people have theorized that this may be one of the causes of Alzheimer’s.

Chemical deficiencies are also believed to possibly contribut to the occurrence of Alzheimer’s Disease. Neurotransmitters are necessary for communication between neurons. Many victims of Alzheimer’s display diminished levels of acetylcholine. This may influence the decrease in intellectual functioning and behaior that is typical among Alzheimer’s patiernts.

A high level of toxic chemicals may also cause stress that can lead to Alzheimer’s. This includes a rise In the levels of aluminum and mercury among Alzheimer’s patients. It has however been determined that the increase in the levels of these substances is actually probably on of the results of Alzheimer’s rather than a cause.

There are many genetic theories circulating about Alzheimer’s Disease. Though it has not been proven that Alzheimer’s is completely genetic, nor is it always hereditary, there are a few chromosomes that have been identified as carrying Alzheimer’s related genes. These genes show abnormalities that are much more common among people with Alzheimer’s than among peopel who do not have Alzheimer’s. There are genetic markers on Chromosomes 14 and 21 that have been associated with patients that have experienced early onset Alzheimer’s Disease. The genetic markers discovered on Chromosome 19 have been associated with patients that have experienced a later development of Alzheimer’s. All of the genetic information however, is still unclear.

Another theory about the cause of Alzheimer’s Disease is the Autoimmune Theory. This theory suggests that among some patients with Alzheimer’s, their immune system attacks the body’s tissues, specifically brain tissues. Certain anti-brain antibodies have been discovered, but further research is being done to determine their exact role in Alzheimer’s Disease.

There is also a theory that Alzheimer’s is caused ny a virus that changes brain tissues, but a specific virus and its

Works Cited

1.) The Alzheimer’s Association Homepage. This page offers basic information about Alzheimer’s Disease.

2.) About Alzheimer’s: Alzheimer’s Association, Northwestern Virginia. This page also offers basic information about Alzheimer’s Disease.

3.) ..... This page offers basic information about Alzheimer’s as well as information on Alzheimer’s and genetics and Alzheimer’s effects on the nervous system.

4.) The Genetics of Alzheimer’s Disease. This page offers genetic information about Alzheimer’s.

5.) More Information About Neurofibrillary Tangles.

6.) Senile Plaques and Neurofibrillary Tangles.

7.) Risk Factors for Alzheimer’s Disease: Who is at Risk.

8.) New Findings on Alzheimer’s Disease Offers Clues on Causes, Diagnosis, and Treatment. This page offers basic information on Alzheimer’s as well as information about genetics and treatment.