Diseases and Disorders

The Spreading of Alzheimer’s Disease Through the Brain

Ali Bauer


Introduction

Alzheimer’s disease was first discovered in 1907 by the German Psychiatrist Alois Alzheimer. The disease has a slow progression affecting one out of ten people over the age of sixty-five.  It takes eight to ten years for the disease to reach its critical stage, ending in death, and presently there is no preventive medication {2}. The disease is mainly caused by the accumulation of two unusual proteins that lead to neurodegeneration. Neurofibrillary tangles and senile plaque are the two protein types causing Alzheimer’s disease. They do this by disrupting neurons and destroying important cells necessary for life {3}.  Scientists are curious as to what might cure this disease, but a remedy has not yet been identified.


 

Long Term Damage and the Effects

    The condition affects the brain and causes loss of the normal ability to function.  Alzheimer’s disease comes in phases and gradually worsens over a long period of time {2}.  In the initial stages of the disease, the patient will suffer just from lack of memory. As the disease progresses, the patent will battle loss of language recognition and the ability to make gestures {1}.  Death will soon follow, as cells are depleted, and there is no known cure for this deadly disease {2}.

 

Senile Plaque and Neurofibrillary Tangles

    Alzheimer’s disease mainly involves two different types of  abnormal proteins: senile plaque and neurofibrillary tangles.  A large protein, amyloid precursor protein or APP, is found on the surface of neurons.  APP is normally sectioned by enzymes which free amyloid beta proteins and then cleared from the body.  In the case of Alzheimer’s disease, there is an abundance of amyloid beta due to an imbalance and lack of regulation.  The surplus of the protein is assembled together and form senile plaques.

    Additionally, the neurons in the human brain transfer information by sending a signal from its soma to the synapse as a form of communication.  The information transferred passes through the neuronal skeleton, which is composed of microtubules. The microtubules of the neuronal skeleton are stabilized by the normal tau proteins.  In the case of Alzheimer’s disease, the tau protein becomes abnormal and detaches from the microtubules, breaking apart the vital neuronal skeleton. The defective tau proteins come together and produce filaments in the neuron.  Without the skeleton, the neuron unravels and connections between it and other neurons are broken. The unnatural accumulation of tau filaments in the neuron makes neurofibrillary tangles, which eventually destroys the entire neuron.

    The plaques and tangles originate in the hippocampus, the area in the brain where memories are formed, and eventually spread throughout the brain.  Over the course of many years, the plaques and tangles destroy the hippocampus, and memories, as a result, are harder to form.  The tangles and plaques then spread to the front of the brain where language is processed. Neurons are destroyed by the infestation of abnormal proteins, and it is harder for the patient to speak and understand speech.  The plaques and tangles continue to progress and attack the section of the brain where logical thoughts are processed. The victim might suffer from hallucinations, as it becomes harder for them to distinguish reality from delusion. Next, the area of the brain in which emotions are regulated gets consumed.  The patient loses complete control over their emotional capabilities and mood. Finally, the plaques and tangles travel to the prefrontal cortex, where executive function is regulated. The progressive neurodegeneration of different brain regions ultimately becomes fatal{3}.

    The oldest and most impactful memories are forgotten and the brain cannot distinguish between what did and did not happen.  Senses are distorted, and their feelings do not correspond to what is happening around them {1}. At the critical stage, balance and coordination is majorly impaired, and, eventually, regulations of breathing and circulation fail. These failures in the respiratory and cardiovascular systems result in death. The lack of preventive measures for the onset of Alzheimer's leads to the progression of this disease, and inevitably, death {4}.

 

Searching for a Solution

    Awareness of the disease has grown greatly over the years, but a cure is still greatly needed.  Scientists are investigating the evolution of senile plaques and neurofibrillary tangles and are searching for a solution.  With more research being gathered every day, the hope of finding a cure continues to flourish {1}.


References


  1. Howard, Crystal. “Alzheimer's Disease: Symptoms, Stages, Life-Expectancy.” MedicineNet, www.medicinenet.com/alzheimers_disease_causes_stages_and_symptoms/article.htm.

  2. Smith, BPharm Yolanda. “Alzheimer's tangles and plaques: what's the difference?” News-Medical.net, 10/12/15, www.news-medical.net/health/Alzheimere28099s-tangles-and-plaques-whate28099s-the-difference.aspx.

  3. “Alzheimer's Disease Fact Sheet.” National Institute on Aging, U.S. Department of Health and Human Services, 17/9/16, www.nia.nih.gov/health/alzheimers-disease-fact-sheet.

  4. “Memory Loss & 10 Early Signs of Alzheimer's.” Alzheimer's Association, Alzheimer's Association, 2009, www.alz.org/alzheimers_disease_10_signs_of_alzheimers.asp.

Ali Bauer

Ali Bauer


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