Tuesday, September 1, 2009

Alzheimer's Disease World: Glossary

When you, members of your family, or your friends enter the new world – The World of Alzheimer’s Disease – there is a new language associated with multiple scientific words, which you never have any use before. Now you need to learn the language to understand the deep meanings of the diagnosis, treatments, and doctors’ recommendations.

For your convenience, I have compiled a brief summary of the specific terms, you might stumble upon in the posts on this blog, in other related articles, during consultations with the medical professionals, or trying to understand the documentation and prescriptions.

  • Acetylcholine—a neurotransmitter that plays an important role in many neurological functions, including learning and memory.
  • Activities of daily living (ADLs) - Personal care activities necessary for everyday living, such as eating, bathing, grooming, dressing and using the toilet.
  • Adjuvant therapy - Treatment provided in addition to the primary treatment.
  • Adverse reaction - An unexpected effect of drug treatment that may range from minor to serious to life- threatening, such as an allergic reaction.
  • Agnosia - An impaired ability to recognize or identify objects, even though sensory abilities are intact.
  • Allele - One of two or more alternative forms of a gene. For example, one allele of the gene for eye color codes for blue eyes, while another allele codes for brown eyes.
  • Ambulation - The ability to walk and move about freely.
  • Amino acids - The basic building blocks of proteins. There are 20 amino acids necessary for human growth and function.
  • Amygdala—an almond-shaped structure involved in processing and remembering strong emotions such as fear. It is part of the limbic system and located deep inside the brain.
  • Amyloid plaque—a largely insoluble deposit found in the space between nerve cells in the brain. Plaques are made of beta-amyloid, other molecules, and different kinds of nerve and non-nerve cells.
  • Amyloid precursor protein (APP)—the larger protein from which beta-amyloid is formed.
  • Aphasia - Difficulty understanding the speech of others and/or expressing oneself verbally.
  • Apolipoprotein E—a protein that carries cholesterol in blood and that appears to play some role in brain function. The gene that produces this protein comes in several forms, or alleles: ε2, ε3, and ε4. The APOE ε2 allele is relatively rare and may provide some protection against AD (but it may increase risk of early heart disease). APOE ε3 is the most common allele and appears to play a neutral role in AD. APOE ε4 occurs in about 40 percent of all people with AD who develop the disease in later life; it increases the risk of developing AD.
  • Apraxia - Difficulty performing motor activities, even though the person's movement, senses, and ability to comprehend what is being asked are still intact. Apraxia is basically a disconnect between the idea of a task and its execution.
  • Asymptomatic - When there are no symptoms or no clear sign that disease is present.
  • Autonomy - A person’s ability to make independent choices.
  • Axon—the long extension from a neuron that transmits outgoing signals to other cells.
  • Beta-amyloid—a part of the amyloid precursor protein found in plaques, the insoluble deposits outside neurons.
  • Biomarker - Used to indicate or measure a biological process; for example, levels of a specific protein in blood or spinal fluid. Detecting biomarkers specific to a disease can aid in the identification, diagnosis and treatment of affected individuals, as well as people who may be at risk but who do not yet have symptoms.
  • Brain-derived neurotrophic factor (BDNF)—a growth factor that stimulates survival, growth, and adaptability of some neurons.
  • Brain stem—the portion of the brain that connects to the spinal cord and controls automatic body functions, such as breathing, heart rate, and blood pressure.
  • Calcium channel blocker - A drug that blocks the entry of calcium into cells, thereby reducing activities that require calcium, such as the transmission of nerve impulses. Calcium channel blockers are used primarily in the treatment of certain heart conditions, but are being studied as potential treatments for Alzheimer’s disease.
  • Capillary—a tiny blood vessel. The brain has billions of capillaries that carry oxygen, glucose (the brain’s principal source of energy), nutrients, and hormones to brain cells so they can do their work. Capillaries also carry away carbon dioxide and cell waste products.
  • Cerebellum—the part of the brain responsible for maintaining the body’s balance and coordination.
  • Cerebral cortex—the outer layer of nerve cells surrounding the cerebral hemispheres.
  • Cerebral hemispheres—the largest portion of the brain, composed of billions of nerve cells in two structures connected by the corpus callosum. The cerebral hemispheres control conscious thought, language, decision making, emotions, movement, and sensory functions.
  • Cerebrospinal fluid—the fluid found in and around the brain and spinal cord. It protects these organs by acting like a liquid cushion and by providing nutrients.
  • Chromosome—a threadlike structure in the nucleus of a cell that contains DNA. DNA sequences make up genes. Most human cells have 23 pairs of chromosomes containing approximately 30,000 genes.
  • Choline acetyltransferase (CAT) - An enzyme that controls the production of acetylcholine. CAT appears to be depleted in the brains of individuals with Alzheimer’s disease.
  • Cholinergic system - The system of nerve cells that uses acetylcholine as its neurotransmitter and is damaged in the brains of individual’s with Alzheimer’s disease.
  • Clinical trial—a research study involving humans that rigorously tests safety, side effects, and how well a medication or behavioral treatment works.
  • Cognitive functions—all aspects of conscious thought and mental activity, including learning, perceiving, making decisions, and remembering.
  • Combativeness - Incidents of aggression.
  • Computed tomography (CT) scan—a diagnostic procedure that uses special x-ray equipment and computers to create cross-sectional pictures of the body.
  • Corpus callosum—thick bundles of nerve cell fibers that connect the two cerebral hemispheres.
  • Dementia—a broad term referring to a decline in cognitive function to the extent that it interferes with daily life and activities.
  • Dendrite—a branch-like extension of a neuron that receives messages from other neurons.
  • Differential diagnosis - The clinical evaluation of possible causes of dementia to rule out all other factors before settling on Alzheimer’s disease as a diagnosis.
  • DNA (deoxyribonucleic acid)—a long, double-stranded molecule within the nucleus of the cell that forms chromosomes and genes.
  • Double-blind, placebo-controlled study - A research procedure in which neither researchers nor patients know who is receiving the experimental substances or treatment and who is receiving a placebo.
  • Dysphasia - The inability to find the right word or understand the meaning of a word.
  • Early-onset Alzheimer’s disease—a rare form of AD that usually affects people between ages 30 and 60. It is called familial AD (FAD) if it runs in the family. Early-onset Alzheimer’s disease sometimes is associated with mutations in genes located on chromosomes 1, 14 and 21.
  • Entorhinal cortex—an area deep within the brain where damage from AD often begins.
  • Enzyme—a protein that causes or speeds up a biochemical reaction.
  • Estrogen - A hormone produced by the ovaries and testes. It stimulates the development of secondary sexual characteristics and induces menstruation on women. Estrogen is important for maintaining normal brain function and development of nerve cells.
  • Excitotoxicity - The over-stimulation of nerve cells by nerve impulses. Excitotoxicity often leads to cell damage or cell death.
  • Fatty acids - Acids within the body derived from the breakdown of fats.
  • Free radical—a highly reactive molecule (typically oxygen or nitrogen) that combines easily with other molecules because it contains an unpaired electron. The combination with other molecules sometimes damages cells.
  • Gait - A person’s manner of walking. People in the later stages of Alzheimer’s disease often have a "reduced gait," which means their ability to lift their feet as they walk has diminished.
  • Gene—the biologic unit of heredity passed from parent to child. Genes are segments of DNA and contain instructions that tell a cell how to make specific proteins.
  • Genetic risk factor—a variant in a cell’s DNA that does not cause a disease by itself but may increase the chance that a person will develop a disease.
  • Glial cell—a specialized cell that supports, protects, or nourishes nerve cells.
  • Glutamate - A chemical in the brain that plays a key role in memory, learning, and information processing. Dysfunction of the glutamate system has been associated with Alzheimer’s.
  • Hippocampus—a structure in the brain that plays a major role in learning and memory and is involved in converting short-term to long-term memory.
  • Hypothalamus—a structure in the brain under the thalamus that monitors activities such as body temperature and food intake.
  • Incontinence - Loss of bladder and/or bowel control.
  • Inflammatory response - The immune system’s normal response to tissue injury or abnormal stimulation caused by a physical, chemical or biological substance.
  • Instrumental activities of daily living (IADLs) - Secondary level of activities (different from ADLs, such as eating, dressing and bathing) important to daily living, such as cooking, writing and driving.
  • Late-onset Alzheimer’s disease The most common form of Alzheimer’s disease, usually occurring after age 65. Late-onset Alzheimer’s disease affects almost half of all people over the age of 85 and may or may not be hereditary.
  • Layering - Behavior that involves inappropriately changing or layering clothing on top of one another.
  • Limbic system—a brain region that links the brain stem with the higher reasoning elements of the cerebral cortex. It controls emotions, instinctive behavior, and the sense of smell.
  • Magnetic resonance imaging (MRI)—a diagnostic and research technique that uses magnetic fields to generate a computer image of internal structures in the body. MRIs are very clear and are particularly good for imaging the brain and soft tissues.
  • Metabolism—all of the chemical processes that take place inside the body. In some metabolic reactions, complex molecules are broken down to release energy. In others, the cells use energy to make complex compounds out of simpler ones (like making proteins from amino acids).
  • Microglia (microglia cells) - A type of immune cell found in the brain. Microglia cells are scavengers, engulfing dead cells and other debris. In Alzheimer’s disease, microglia cells are found associated with dying nerve cells and amyloid plaques.
  • Microtubule—an internal support structure for a neuron that guides nutrients and molecules from the body of the cell to the end of the axon.
  • Mild cognitive impairment (MCI)—a condition in which a person has memory problems greater than those expected for his or her age, but not the personality or cognitive problems that characterize AD.
  • Mini-Mental State Examination - A standard mental status exam routinely used to measure a person’s basic cognitive skills, such as short-term memory, long-term memory, orientation, writing and language.
  • Mitochondria - Components found in cells that serve as primary energy sources for cellular functions.
  • Mutation—a permanent change in a cell’s DNA that can cause a disease.
  • Myelin—a whitish, fatty layer surrounding an axon that helps the axon rapidly transmit electrical messages from the cell body to the synapse.
  • Nerve cell (neuron) - The basic working unit of the nervous system. The nerve cell typically is composed of a cell body containing the nucleus, several short branches (dendrites), and one long arm (the axon) with short branches along its length and at its end. Nerve cells send signals that control the actions of other cells in the body, such as other nerve cells and muscle cells.
  • Nerve growth factor (NGF)—a substance that maintains the health of nerve cells. NGF also promotes the growth of axons and dendrites, the parts of the nerve cell that are essential to its ability to communicate with other nerve cells.
  • Neurodegenerative disease—a disease characterized by a progressive decline in the structure, activity, and function of brain tissue. These diseases include AD, Parkinson’s disease, frontotemporal lobar degeneration, and dementia with Lewy bodies. They are usually more common in older people.
  • Neurofibrillary tangle—a filamentous collection of twisted and hyperphosphorylated tau found in the cell body of a neuron in AD.
  • Neurotransmitter—a chemical messenger between neurons. These substances are released by the axon on one neuron and excite or inhibit activity in a neighboring neuron.
  • Nucleus—the structure within a cell that contains the chromosomes and controls many of its activities.
  • Oxidative damage—damage that can occur to cells when they are exposed to too many free radicals.
  • Peripheral nervous system (PNS) - One of the two major divisions of the nervous system. Nerves in the PNS connect the central nervous system with sensory organs, other organs, muscles, blood vessels and glands.
  • Perseveration - The persistent repetition of an activity, word, phrase or movement, such as tapping, wiping and picking.
  • Pillaging - Taking things that belong to someone else. A person with dementia may think something belongs to him or her, even when it clearly does not.
  • Positron emission tomography (PET)—an imaging technique using radioisotopes that allows researchers to observe and measure activity in different parts of the brain by monitoring blood flow and concentrations of substances such as oxygen and glucose, as well as other specific constituents of brain tissues.
  • Presenilins - Proteins that may be linked to early-onset Alzheimer’s disease.
  • Prions - Protein segments that may cause infection and may lead to some forms of dementia.
  • Pseudodementia - A severe form of depression resulting from a progressive brain disorder in which cognitive changes mimic those of dementia.
  • Psychosis - A general term for a state of mind in which thinking becomes irrational and/or disturbed. Psychosis refers primarily to delusions, hallucinations and other severe thought disturbances.
  • Receptor agonist - A substance that mimics a specific neurotransmitter, is able to attach to that neurotransmitter’s receptor and thereby produces the same action the neurotransmitter usually produces. Drug often are designed as receptor agonists to treat a variety of diseases and disorders in which the original chemical substance is missing or depleted.
  • Reminiscence - A life review activity aimed at surfacing and reviewing positive memories and experiences.
  • Repetitive behavior - Repeated questions, stories and outbursts or specific activities done over and over again, common in people with dementia.
  • Safe Return - The Alzheimer’s Association’s nationwide identification, support and registration program that assists in the safe return of individuals with Alzheimer’s disease or other dementias who wander and become lost.
  • Secretase - A group of enzymes found in brain cells (alpha-secretase, beta-secretase, and gamma-secretase. The secretases function to degrade APP. The abnormal degradation of APP can result in the accumulation of amyloid in the brain and the development of Alzheimer's disease.
  • Shadowing - Following, mimicking and interrupting behaviors that people with dementia may exhibit.
  • Single photon emission computed tomography (SPECT)—an imaging technique that allows researchers to monitor blood flow to different parts of the brain.
  • Sundowning  - Unsettled behavior evident in the late afternoon or early evening.
  • Synapse—the tiny gap between nerve cells across which neurotransmitters pass.
  • Tau—a protein that helps to maintain the structure of microtubules in normal nerve cells. Abnormal tau is a principal component of the paired helical filaments in neurofibrillary tangles.
  • Thalamus—a small structure in the front of the cerebral hemispheres that serves as a way station that receives sensory information of all kinds and relays it to the cortex; it also receives information from the cortex.
  • Transgenic—an animal that has had a gene (like human APP) inserted into its chromosomes. Mice carrying the mutated human APP gene often develop plaques in their brains as they age.
  • Ventricle—a cavity within the brain that is filled with cerebrospinal fluid.
  • Vesicle—a small container for transporting neurotransmitters and other molecules from one part of the neuron to another.

Sources and Additional Information:
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