The image on the left is the outside of the brain, viewed from the side, showing the major lobes (frontal, parietal, temporal and occipital) and the brain stem structures (pons, medulla oblongata, and cerebellum).
The image on the right is a side-view showing the location of the limbic system inside the brain. The limbic system consists of a number of structures, including the fornix, hippocampus, cingulate gyrus, amygdala, the parahippocampal gyrus and parts of the thalamus.The hippocampus is one of the first areas affected by Alzheimer's disease. As the disease progresses, damage extends throughout the lobes.
Glossary of Terms for an Anatomy of the Brain
Amygdala – limbic structure involved in many brain functions, including emotion, learning and memory. It is part of a system that processes "reflexive" emotions like fear and anxiety.
Cerebellum – governs movement.
Cingulate gyrus – plays a role in processing conscious emotional experience.
Fornix – an arch-like structure that connects the hippocampus to other parts of the limbic system.
Frontal lobe – helps control skilled muscle movements, mood, planning for the future, setting goals and judging priorities.
Hippocampus – plays a significant role in the formation of long-term memories.
Medulla oblongata – contains centers for the control of vital processes such as heart rate, respiration, blood pressure, and swallowing.
Limbic system – a group of interconnected structures that mediate emotions, learning and memory.
Occipital lobe – helps process visual information.
Parahippocampal gyrus – an important connecting pathway of the limbic system.
Parietal lobe – receives and processes information about temperature, taste, touch, and movement coming from the rest of the body. Reading and arithmetic are also processed in this region.
Pons – contains centers for the control of vital processes, including respiration and cardiovascular functions. It also is involved in the coordination of eye movements and balance.
Temporal lobe – processes hearing, memory and language functions.
Thalamus – a major relay station between the senses and the cortex (the outer layer of the brain consisting of the parietal, occipital, frontal and temporal lobes).
How the Brain and Nerve Cells Change During Alzheimer's Disease
Illustration by Bob Morreale, provided courtesy of the American Health Assistance Foundation.
One of the hallmarks of Alzheimer's disease is the accumulation of amyloid plaques between nerve cells (neurons) in the brain. Amyloid is a general term for protein fragments that the body produces normally. Beta-amyloid is a fragment of a protein that is snipped from another protein called amyloid precursor protein (APP). In a healthy brain, these protein fragments would be broken down and eliminated. In Alzheimer's disease, the fragments accumulate to form hard, insoluble plaques.
Neurofibrillary tangles consist of insoluble twisted fibers that are found inside of the brain's cells. They primarily consist of a protein called tau, which forms part of a structure called a microtubule. The microtubule helps transport nutrients and other important substances from one part of the nerve cell to another (the axon is the long threadlike extension that conducts nerve impulses away from the body of a nerve cell, and dendrites are any of the short branched threadlike extensions that conduct nerve impulses towards the nerve cell body. In Alzheimer's disease the tau protein is abnormal and the microtubule structures collapse.
There is an overall shrinkage of brain tissue as Alzheimer's disease progresses. In addition, the ventricles, or chambers within the brain that contain cerebrospinal fluid, are noticeably enlarged. In the early stages of Alzheimer's disease, short-term memory begins to decline when the cells in the hippocampus, which is part of the limbic system, degenerate. The ability to perform routine tasks also declines. As Alzheimer's disease spreads through the cerebral cortex (the outer layer of the brain), judgment declines, emotional outbursts may occur and language is impaired. Progression of the disease leads to the death of more nerve cells and subsequent behavior changes, such as wandering and agitation. The ability to recognize faces and to communicate is completely lost in the final stages. Patients lose bowel and bladder control, and eventually need constant care. This stage of complete dependency may last for years before the patient dies. The average length of time from diagnosis to death is 4 to 8 years, although it can take 20 years or more for the disease to run its course.
3D Hippocampal Segmentation & Shape Analysis in Alzheimer's Disease
The hippocampus – named for its shape – is a brain structure located inside the temporal lobe that plays a part in memory and navigation of a person. More importantly, it is one of the first regions in the brain to be attacked in individuals suffering from Alzheimer’s disease, and is thus an important indicator for early detection of the disease. With the aim being to characterize the shape and rate of change over time in patients and controls and linking such findings to clinical observations. This will then be extended to analyze other brain structures and examine how they change as this disease progresses.
These images represent a cross-section of the brain as seen from the front. The cross-section on the left represents a brain from a normal individual and the one on the right represents a brain with Alzheimer's disease.
In Alzheimer's disease, there is an overall shrinkage of brain tissue. The grooves or furrows in the brain, called sulci (plural of sulcus), are noticeably widened and there is shrinkage of the gyri (plural of gyrus), the well-developed folds of the brain's outer layer. In addition, the ventricles, or chambers within the brain that contain cerebrospinal fluid, are noticeably enlarged. In the early stages of Alzheimer's disease, short-term memory begins to decline (see box labeled ‘memory') when the cells in the hippocampus, which is part of the limbic system, degenerate. The ability to perform routine tasks also declines. As Alzheimer's disease spreads through the cerebral cortex (the outer layer of the brain), judgment declines, emotional outbursts may occur and language is impaired. Progression of the disease leads to the death of more nerve cells and subsequent behavior changes, such as wandering and agitation. The ability to recognize faces and to communicate is completely lost in the final stages. Patients lose bowel and bladder control, and eventually need constant care. This stage of complete dependency may last for years before the patient dies. The average length of time from diagnosis to death is 4 to 8 years, although it can take 20 years or more for the disease to run its course.
The formation of amyloid plaques and neurofibrillary tangles are thought to contribute to the degradation of the neurons (nerve cells) in the brain and the subsequent symptoms of Alzheimer's disease.
AMYLOID PLAQUES
One of the hallmarks of Alzheimer's disease is the accumulation of amyloid plaques between nerve cells (neurons) in the brain. Amyloid is a general term for protein fragments that the body produces normally. Beta-amyloid is a fragment of a protein that is snipped from another protein called amyloid precursor protein (APP). In a healthy brain, these protein fragments would be broken down and eliminated. In Alzheimer's disease, the fragments accumulate to form hard, insoluble plaques.
NEUROFIBRILLARY TANGLES
Neurofibrillary tangles consist of insoluble twisted fibers that are found inside of the brain's cells. They primarily consist of a protein called tau, which forms part of a structure called a microtubule. The microtubule helps transport nutrients and other important substances from one part of the nerve cell to another. In Alzheimer's disease, however, the tau protein is abnormal and the microtubule structures collapse.
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