The image on the left is a side view of the outside of the brain, 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.
yet weighs only about three pounds. It has a texture similar to firm jelly.
The Three Main Parts:
1. The cerebrum fills up most of your skull. It is involved in remembering, problem solving, thinking, and feeling. It also controls movement.
2. The cerebellum sits at the back of your head, under the cerebrum. It controls coordination and balance.
3. The brain stem sits beneath your cerebrum in front of your cerebellum. It connects the brain to the spinal cord and controls automatic functions such as breathing, digestion, heart rate and blood pressure.
The real work of your brain goes on in individual cells. An adult brain contains about 100 billion a. nerve cells , or neurons, with b. branches that connect at more than 100 trillion points. Scientists call this dense, branching network a "neuron forest.“ c . Signals travel through the neuron forest form the basis of memories, thoughts, and feelings.
Neurons are the chief type of cell destroyed by Alzheimer's disease.
Signals that form memories and thoughts move through an individual nerve cell as a . tiny electrical change
Nerve cells connect to one another at b . synapses . When a charge reaches a synapse, it may trigger release of tiny bursts of chemicals called c . neurotransmitters . The neurotransmitters travel across the synapse, carrying signals to other cells. Scientists have identified dozens of neurotransmitters.
Alzheimer's disease disrupts both the way electrical charges travel within cells and the activity of neurotransmitters.
100 billion nerve cells… 100 trillion synapses… dozens of neurotransmitters… This “strength in numbers” provides your brain’s raw material. Over time, our experiences create patterns in signal type and strength. These patterns of activity explain how, at the cellular level, our brains code our thoughts, memories, skills and sense of who we are.
The positron emission tomography (PET) scan on the left shows typical patterns of brain activity associated with:
a. Reading words
b. Hearing words
c. Thinking about words
d. Saying words
Activity is highest in red areas and then decreases through the other colors of the rainbow from yellow to blue - violet .
Specific activity patterns change throughout life as we meet new people, have new experiences and acquire new skills. The patterns also change when Alzheimer’s disease or a related disorder disrupts nerve cells and their connections to one another.
Plaques form when protein pieces called a. beta- amyloid (BAY-tuh AM-uh-loyd) clump together. Beta-amyloid comes from a larger protein found in the fatty membrane surrounding nerve cells.
Beta-amyloid is chemically "sticky" and gradually builds up into b. plaques.
The most damaging form of beta-amyloid may be c. groups of a few pieces rather than the plaques themselves. The small clumps may block cell-to-cell signaling at synapses. They may also activate immune system cells that trigger inflammation and devour disabled cells.
In mild to moderate stages, brain regions important in a. memory and b. thinking and planning develop more plaques and tangles than were present in early stages. As a result, individuals develop problems with memory or thinking serious enough to interfere with work or social life. They may also get confused and have trouble handling money, expressing themselves and organizing their thoughts. Many people with Alzheimer’s are first diagnosed in these stages.
Plaques and tangles also spread to area
c. Speaking and understanding speech
d. Your sense of where your body is in
relation to objects around you
As Alzheimer’s progresses, individuals may experience changes in personality and behavior and have trouble recognizing friends and family members.
In advanced Alzheimer’s disease, most of the cortex is seriously damaged. The brain shrinks dramatically due to widespread cell death. Individuals lose their ability to communicate, to recognize family and loved ones and to care for themselves.
Progressive mental deterioration in old age has been recognized and described throughout history. However, it was not until 1906 that a German physician, Dr. Alois Alzheimer, specifically identified a collection of brain cell abnormalities as a disease. One of Dr. Alzheimer’s patients died after years of severe memory problems, confusion and difficulty understanding questions. Upon her death, while performing a brain autopsy, the doctor noted dense deposits surrounding the nerve cells (neuritic plaques). Inside the nerve cells he observed twisted bands of fibers (neurofibrillary tangles). Today, this degenerative brain disorder bears his name, and when found during an autopsy, these plaques and tangles mean a definite diagnosis of Alzheimer's disease (AD).
Since its discovery more than 100 years ago, there have been many scientific breakthroughs in AD research. In the 1960s, scientists discovered a link between cognitive decline and the number of plaques and tangles in the brain. The medical community then formally recognized Alzheimer’s as a disease and not a normal part of aging. In the 1970s, scientists made great strides in understanding the human body as a whole, and AD emerged as a significant area of research interest. This increased attention led in the 1990s to important discoveries and a better understanding of complex nerve cells in the brains of AD patients. More research was done on AD susceptibility genes, and several drugs were approved to treat the cognitive symptoms of the disease.
Over the last decade, scientists have substantially progressed in understanding potential environmental, genetic and other risk factors for AD, the processes leading to formation of plaques and tangles in the brain, and the brain regions that are affected. Specific genes related to both the early-onset and late-onset forms of AD have been identified, but genetic risk factors alone do not fully explain its causes, so researchers are actively exploring environment and lifestyle to learn what role they might play in the development of this disease. More effective treatment options have been approved by the Food and Drug Administration (FDA). However, AD is still incurable. The drugs currently in use treat only the symptoms, not the cause of the disorder, and they only slow the progression of cognitive decline.
Dementia is a decline in cognitive function or mental ability – thinking, reasoning and remembering. People with dementia have difficulty independently carrying out daily tasks they have performed routinely throughout their lives. The most common forms of dementia in the elderly are Alzheimer’s disease and vascular dementia, a hardening of the arteries in the brain that causes blockage in blood flow. These two conditions account for the vast majority of cases, and although their symptoms can sometimes be managed, they are irreversible. The dementia associated with Alzheimer’s will progressively worsen.
Dementia can also be caused by infection; drug interactions; metabolic disorders of the thyroid, liver, pancreas or kidneys; nutritional deficiencies, especially the lack of vitamin B-12; head injury; brain tumors; depression; or other progressive diseases such as Parkinson's, Lewy-body, Huntington’s or Pick’s.
If a decline in mental function makes an impression on friends and family, and begins to interfere with daily activities, employment tasks, social interactions, and family chores, set up an appointment with a doctor to accurately determine the underlying cause of the symptoms.