Alzheimer Disease Progression and Stages

The brain is a three-pound fascinating organ that is enclosed and protected by the cerebrospinal fluid. The brain is responsible for the coordination of the human’s behavior, thoughts, and emotions. Part of the brain's information-processing network includes neurons, or cells that transmit signals throughout the brain. Neurons send signals through neurotransmitters, which are chemicals some release and others receive. These chemicals essentially let the parts of the brain communicate and maintain a normal function and pathology for the human body’s physiological system.

The essential neurotransmitters which keep the brain healthy are dopamine, serotonin, and norepinephrine. Dopamine acts as the communicator between nerve cells and the nervous system. It is responsible for the feelings of pleasure and positive emotions. Serotonin is the neurotransmitter associated with memory and learning. Serotonin is also linked to the regeneration of brain cells that also helps ease the symptoms of many mood disorders. Norepinephrine kicks the body into gear by stimulating the brain to signal the body for action. Pathological disease such as Alzheimer's disrupts the physiological network of the brain. The onset of Alzheimer’s disease gradually destroys these neurotransmitters leading to complications and ultimately death.

Alzheimer's disease’s signature sign is a loss of memory and other cognitive functions. Progression of the disease leads to disruption of brain and bodily functions, resulting in severe dementia. A major function of the brain is memory formation and regulation of hormones and chemicals of the body. This section of the paper will discuss the progression of the disease and how the underlying pathology selectively impairs the neurons involved in memory and storage and chemical hormone regulation.

The progression of Alzheimer’s disease can typically be identified with the presence of amyloid plaques and neurofibrillary tangles in the brain. The protein peptide plaques and neurofibrillary tangles eventually cause atrophy to the cortical and subcortical structures of the brain. Neurofibrillary tangles are the warped protein fibrils of the nerve cells in the tissue of the brain. These protein fibrils are supporting structures in the microtubules in the nervous system. In a healthy function, the fibrils supports the neurons by aiding in the transportation of nutrients to the rest of the cells. Alzheimer’s disease destroys these protein fibrils by the invasion of phosphate molecules which attaches onto the protein. Due to the overwhelming amount of the phosphate molecules the microtubule becomes destabilized, thus, creating more tangles in the brain. As a result, the entire neuronal network of the brain is gradually ravaged by neurofibrillary tangles.

The toxic effect the plaque and tangles have on the brain is detrimental to the neurotransmitters. For example, loss of neurons containing acetylcholine leads to cognitive impairment. Alzheimer’s disease is not isolated to a specific region of the brain but rather the chemical function as a whole. Further destruction of the major neurotransmitters of the brain includes reduced levels of serotonin in the cortical and hippocampal. Why are the serotonin receptors so important? Both G-protein-duo receptor groups and ligand-gated ion channels located in the central and peripheral nervous systems promote both excitatory and inhibitory neurotransmission.

The receptors of serotonin serve as the regulator of major neurotransmitters such as acetylcholine, dopamine, epinephrine / norepinephrine, epinephrine / norepinephrine, GABA, and glutamate. Aside from neurotransmitters, serotonin also regulates the release of many hormones like prolactin, vasopressin, cortisol, oxytocin, and corticotropin. When these serotonin receptors are disrupted, patients will start displaying various biological and neurological symptoms such as aggression, anxiety, loss of appetite, decreased of cognitive function--memory, mood, and thermoregulation.

The following are complications that arise from early to late stages of Alzheimer's disease The early preclinical stage of Alzheimer’s disease is gradual. Amyloid plaques and neurofibrillary tangles are already present in the brain. Patients will start to experience a decline in memory due to the disruption of serotonin in the brain. For example, patients may not be able to recall a recent conversation or appointments made. Decision making becomes difficult. As the Alzheimer’s disease progresses, further complications, due to the disruptions of the hormones secreted by the brain, is a change in personality. Norepinephrine which controls mood is affected so the patient will start to display anger and aggressive mood.

During the late to final stages of Alzheimer’s disease individuals lose track of where they are, the day of the week or the season. This is because the serotonin receptors are completely destroyed. Without these neurotransmitters, the brain is operating without a pilot. Patients will also undergo significant changes in personality and behavior. It's not unusual for people with moderate dementia stage to develop unfounded suspicions— for example, they may accuse friends and family of theft or wrongfully suspect their spouse of being unfaithful.

In the final stage of Alzheimer’s disease, the patient is in full severe dementia. Figuratively speaking, it is like an airplane losing control and dropping out of the sky because there is no controller behind the wheel. Mental functions cease to exist and the patient is lost in its shell. Movement and physical capabilities are inhibited. Patients may no longer speak coherently. Basic tasks such as going to the restroom or eating and swallowing is extremely difficult.