Neurotransmitters: The Messengers
AD also destroys the way some neurons “talk” to each other. Normally, a neuron receives messages from other neurons at its dendrites. The information passes to the cell body and down its axon as and electrical impulse. This electrical impulse triggers chemicals called neurotransmitters to empty into the small gap (synapse) and the massages continues. AD attacks the neurotransmitter acetylcholine ( located at the nucleus basalis of Meynert) and causes a profound effect on memory loss.
Affected Areas of the Brain
Alzheimer’s affects the cerebral cortex of the temporal, parietal, and frontal lobes of the brain, gradually impairing their normal functions. The critical structures deep inside the brain that process and relay information to the cerebral cortex and other areas are also affects; these structures include the hippocampus, the amygdala, and the nucleus basalis of Meynert
Amyloid Plaques (also called senile plaques) are clumps of beta amyloid protein that are surrounded by abnormal nerve endings called neuritis. These plaques are found between the neurons in the cerebral cortex of the brain. Recent research indicates that random amyloid plaques are seen in normal elderly as well as those with early AD. However, when these plaques occur in clusters, they create a harmful effect and contribute to the development of AD. Researchers are developing medications that would stop or reverse the development of beta amyloid protein.
Physical Changes in the Cerebral Cortex
The brain in formed of two tissue types know as the grey and white matter. The grey matter in the cerebral cortex is the outer brain tissue that contains neuron cell bodies. The part of neurons called axons extend deep into the inner tissue, or white matter, to form pathways connecting the different functional areas of the brain. When large numbers of neurons are damaged, gaps occur in communication severely limiting one’s ability to think and remember. In AD, the greatest loss of neurons occurs in the cortex of the temporal and parietal lobes, causing the grey matter of that area to shrink or atrophy.
Abnormal Cellular Structures Involved in Alzheimer’s Disease
How and why neurons die in AD is largely unknown. However, several characteristic abnormal cellular structures in the neurons and brain, which scientists believe cause cell malfunction or cell death, are found in the brains of many AD patients. These structures include excessive granulovacuoles, neurofibrillary tangles, and amyloid plaques.
Granulovacuolar Degeneration
Is found inside the neurons of the hippocampus. An abnormally high number of fluid-filled spaces, called vacuoles, enlarge the cell’s body possibly causing the cell to malfunction or die.
Neurofibrillary Tangles
are bundles of filaments inside the neurons that abnormally twist around one another. Many neurofibrillary tangles are found in areas of the brain associated with memory and learning (hippocampus), fear and aggression (amygdala), and thinking (cerebral cortex). Scientists believe the neurofibrillary tangles play a role in the memory loss and personality changes seen in Alzheimer’s Disease.
Alzheimer’s Disease
The most common form of demaintia is Alzheimer’s Disease (AD), a slowly progressive disorder that destroys the neurons and communication pathways of the brain. It is the seventh leading cause of death in adults in the U.S. and it is perhaps the most devastating chronic disease for patients and their families.
The Aging Brain and Dementia
At birth, the brain contains as many nerve cell called neurons as it will ever have – many billions of neurons! Unlike other cell of our body, such as skin or bone, neuron cannot reproduce themselves. Therefore, as we age, neurons that die from normal wear and tear and injury are not replaced. The normal effects of aging can cause mild forgetfulness and reduced reflexes. However, there are diseases known as dementias that mimic these age-related changes in their early stages. Dementia id characterized by the progressive, yet dramatic, decline of cognitive function.
Diagnosing Alzheimer’s Disease
Unfortunately, certain diagnosis of AD is done only by examining the brain at the time of death when and autopsy can supply and adequate sample of brain tissue. However, a thorough workup can help identify some of the hallmark features of AD and guide doctors toward this diagnosis. For example, blood tests to eliminate the possibility of infectious or metabolic disturbances; an MRI scan to reveal structural problems or history of strokes; and finally, neuropsychological tests to evaluate memory, spatial tasks, reaction time, and executive functioning, all of these tests help identify the areas of cognition that are impaired and distinguish one type of dementia from anther.
Risk Factors
• Age. AD affects 1-2% of seniors 65, and quickly rises to 35-50% by age 85.
• 0n average, people with AD live 8-10 years after they are diagnosed.
• Genetics. Although the causes of AD are largely unknown, in some cases genetic factors are responsible. About 20% of patients with AD will have one or more siblings or parents affected.
• Gender. Women are at a slightly greater risk of developing AD than men, the reason for this still remains unknown.
• Education. An educated, or a higher functioning brain, appears to have an “extra reserve” that can delay the onset or decrease the risk of AD. However, crossword puzzles and other mental exercises have not been shown to protect against AD.
• Exercise. Some studies have suggested that ongoing physical exercise may be helpful in slowing the development or progression of AD.
Stages of Alzheimer’s Disease
Managing AD involves two important consideration:
1. Enabling patients to be as independent as possible while maintaining their quality of life.
2. Providing support for the families. By understanding the general stages of AD, patients and their families can plan for the future.
Stage 1: Early or mind Phase
Some early symptoms of AD go unnoticed because the patient’s social skills cover up these difficulties:
• Continual forgetfulness.
• Difficulty recalling new names and recent conversations.
• Personality changes, such as decreased motivation and drive, or becoming easily upset or anxious.
• Disorientation or becoming lost in familiar surroundings.
Stage 2: Middle or Moderate Phase
• Worsening of memory, especially with current events.
• Depression, withdrawal or agitation.
• Requiring help in decision making and managing personal finances.
• Increasing dependence on others for daily care.
Stage 3: Late or Severe Phase
• Unawareness of time and place.
• Inability to identify close family members at times.
• Increasing insecurity, suspicion and agitation
• Disturbed sleep.
• Slower and more difficult movement and coordination.
• Constant dependence on others for daily care; this may require families to seek nursing home care for their loved one.