Acetylcholine - A neurotransmitter that appears to be involved in learning and memory. Acetylcholine is severely diminished in Alzheimer's disease.

Alzheimer's disease (AD) - A progressive, neurodegenerative disease characterized by loss of function and death of nerve cells in several areas of the brain leading to loss of cognitive function such as memory and language. The cause of nerve cell death is unknown. Alzheimer's disease is the most common cause of dementia.

Apathy - Indifference, lethargy, or general lack of emotion or feeling.

Aspartate - A neurotransmitter; aspartate can be an excitotoxin.

Axons - The "arm" of a nerve cell that normally transmits outgoing signals. Each nerve cell has one axon, which can be over a foot long. A nerve cell communicates with another nerve cell by transmitting signals from the branches at the end of its axon.


Behavioral symptoms - In Alzheimer's disease, the symptoms that relate to action or emotion, such as wandering, depression, anxiety, hostility, and sleep disturbances. See section on behavioral symptoms for further explanation.

Brain - One of the two components of the central nervous system, the brain is the center of thought and emotion. It is responsible for the coordination and control of bodily activities, and the interpretation of information from the senses (sight, hearing, smell, etc.).


Calcium - An element taken in through the diet that is essential for a variety of bodily functions, such as neurotransmission, muscle contraction, and proper heart function. Imbalances of calcium can lead to many health problems, and excess calcium in nerve cells can cause their death.

Calcium channel blocker - A drug that blocks the entry of calcium into cells, thereby prefenting cell dealth and loss of function caused by excess calcium. Calcium channel blockers are used primarily in the treatment of certain heart conditions and stroke, but are being studied as potential treatments for Alzheimer's disease.

Caregiver - The primary person in charge of care of an Alzheimer patient, usually a family member or a designated health care professional.

Cell - The fundamental unit of all organisms; the smallest structural unit that is capable of independent functioning.

Cell body - In nerve cells, this is the central portion containing the cell nucleus, from which axons and dendrites sprout. The cell body is primarily concerned with carrying out the life- sustaining functions of a cell.

Cell membrane - The outer boundary of the cell; the cell membrane helps control what substances enter or exit the cell.

Central nervous system (CNS) - One of the two major divisions of the nervous system. Composed of the brain and spinal cord, the CNS is the control center for the entire body.

Chelation - The process of binding and removing metal ions from the body. Chelation is used to treat metal poisoning, such as lead poisoning.

Choline - A natural substance required by the body that is obtained from various foods, such as eggs; one essential component of acetylcholine.

Choline acetyltransferase (CAT) - An enzyme that controls the production of acetylcholine; appears to be depleted in the brains of Alzheimer patients.

Cholinergic system - The system of nerve cells that uses acetylcholine as its neurotransmitter; nerve cells in the cholinergic system are damaged in the brains of Alzheimer patients.

Cholinesterase - An enzyme that breaks down acetylcholine to stop its action.

Clinical trial - Carefully controlled studies to test the value of various treatments, such as drugs or surgery for disease, in human beings.

Cognitive symptoms - Symptoms that relate to disorders in thought processes, such as learning, comprehension, memory, reasoning, and judging. These symptoms are prominant features of AD. See cognitive symptoms section for further explanation.

Cerebral cortex - The outer portion of the brain, consisting of layers of nerve cells and the pathways that connect them. The cerebral cortex is the part of the brain in which thought processes take place. In Alzheimer's disease, nerve cells in the cerebral cortex die.


Dementia - Loss of intellectual functions, (such as thinking, remembering, and reasoning) of sufficient severity to interfere within an individuals daily functioning.

Dendrites - Branched extensions of the nerve cell body which receives signals from other nerve cells. Each nerve cell usually has many dendrites.

Dialysis - A medical procedure used to remove poisons and excessive amounts of drugs or other substances from blood. Often used in persons with kidney disease.

Dopamine - A neurotransmitter that is essential for normal movement, such as walking. The brains of Parkinson's disease patients are deficient in dopamine.

Dopaminergic system - The system of nerve cells that uses dopamine as its neurotransmitter.

Double-blind, placebo-controlled study - A research procedure in which neither researchers nor patients knows who is receiving the experimental substance or treatment and who is receiving a placebo.


Enzymes - Proteins produced by living organisms that promote or otherwise influence chemical reactions.

Excitotoxin - A chemical substance that can damage and kill nerve cells by overstimulating them.


Glutamate - A neurotransmitter that is normally involved in learning and memory. Under ceratin circumstances it can be an excitotoxin, and appears to cause the death of nerve cells in a variety of neurodegenerative disorders. Early research has shown that glutamate may cause nerve cell death in AD, and further research is being performed to learn more about its possible role in AD.


Hippocampus - A part of the brain that is important for learning and memory.

Informed consent - The agreement of a person (or his or her legally authorized representative) to serve as a research subject, in full knowledge of all anticipated risks and benefits of the experiment.


Metabolism - The complex chemical and physical processes of living organisms that promote growth, sustain life, and enable all other bodily functions to take place.

Monoamine oxidase (MAO) - An enzyme that breaks down certain neurotransmitters, including dopamine, serotonin, and noradrenaline.

Monoamine oxidase inhibitor (MAOI) - A drug that interferes with the action of monoamine oxidase, slowing the breakdown of certain neurotransmitters. Used in the treatment of depression.

Multi-infarct dementia (MID) - Also known as vascular dementia, this form of dementia is caused by a number of strokes in the brain. These strokes can cause specific symptoms, depending on their severity and location, and can cause general symptoms of dementia. MID cannot be treated; once the nerve cells die, they cannot be replaced. However, the underlying condition leading to strokes (e.g., high blood pressure, diabetes) can be treated, which may help prevent further damage.

Multiple sclerosis (MS) - A neurodegenerative disease that damages myelin, the insulation that controls the movement of electrical signals along axons. MS patients show a variety of symptoms (such as loss of coordination, slurred speech, and dizziness), depending on where in the central nervous system the degeneration occurs.

nerve cell (neuron) - The basic working unit of the nervous system. The nerve cell is typically 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 muscle cells.


Nerve growth factor - A protein that promotes nerve cell growth and may protect some types of nerve cells from damage, including nerve cells in the cholinergic system.

Neuritic plaque - Abnormal cluster of dead and dying nerve cells, other brain cells, and protein. Neuritic plaques are one of the characteristic structural abnormalities found in the brains of Alzheimer patients. Upon autopsy, the presence of neuritic plaques and neurofibrillary tangles is used to positively diagnose AD.

Neurodegenerative disorder - A type of neurological disease marked by the loss of nerve cells. See Alzheimer's disease, Parkinson's disease.

Neurofibrillary tangle - Accumulation of twisted protein fragments inside nerve cells. Neurofibrillary tangles are one of the characteristic structural abnormalities found in the brains of Alzheimer patients. Upon autopsy, the presence of neuritic plaques and neurofibrillary tangles is used to positively diagnose AD.

Neurological disorder - Disturbance in structure or function of the central nervous system resulting from developmental abnormality, disease, injury, or toxin.

Neurologist - A physician who diagnoses and treats disorders of the nervous system.

Neuropeptide Y - A substance that sometimes functions as a neurotransmitter. Some research shows that Neuropeptide Y may be involved in Alzheimer's disease.

Neurotransmission - Passage of signals from one nerve cell to another via chemical substances or electrical signals.

Neurotransmitter - Specialized chemical messenger (e.g., acetylcholine, dopamine, norepinephrine, serotonin) produced and secreted by nerve cells that sends a message from one nerve cell to another. Neurotransmitters play different roles throughout the body, many of which are not yet fully understood.

Neurotransmitter system - A group of nerve cells that use the same neurotransmitter to communicate.

Noradrenaline - A neurotransmitter, also called norepinephrine, that plays a role in mood, pain, and possibly learning and memory. Noradrenaline may be involved in AD.

Noradrenergic system - The system of nerve cells that uses noradrenaline (norepinephrine) as its neurotransmitter.

Nucleus - A large body within cells that contains DNA, the genetic material.


Parkinson's disease - A progressive, neurodegenerative disease characterized by the death of nerve cells containing the neurotransmitter dopamine in a specific area of the brain; the cause of nerve cell death is unknown. Parkinson patients have such symptoms as tremors, speech impediments, movement difficulties, and often dementia.

Peripheral nervous system (PNS) - One of the two major divisions of the nervous system. Nerves in the PNS connect the central nervous system (CNS) with sensory organs, other organs, muscles, blood vessels, and glands.

Placebo - A "sugar pill," or sometimes an active drug used for comparison in a drug study. See double-blind, placebo-controlled study.

Plaques and tangles - See neuritic plaque and neurofibrillary tangle.

Psychiatric symptoms - See behavioral symptoms.

Psychiatrist - A physician who specializes in the diagnosis and treatment of behavioral abnormalities and mental diseases.


Receptor - In the nervous system, a site on a nerve cell that receives a specific neurotransmitter; the "message receiver."

Receptor agonist - A substance that mimics a specific neurotransmitter, is able to attach to that neurotransmitter's receptor, and thereby produces the same action that the neurotransmitter usually produces. Drugs are often designed as receptor agonists to treat a variety of diseases and disorders when the original chemical substance is missing or depleted.


Serotonergic system - The system of nerve cells that uses serotonin as their neurotransmitter.

Serotonin - A neurotransmitter that plays a role in mood, sleep, and pain. Serotonin may be involved in sleep.

Side effect - An undesired effect of drug treatment that may range in severity from barely noticeable, to uncorfortable, to dangerous. Side effects are usually predictable.

Somatostatin - A substance that sometimes functions as a neurotransmitter. Some research indicates that somatostatin may be involved in Alzheimer's disease.

Spinal cord - One of the two components of the central nervous system. The spinal cord is the main relay for signals between the brain and the rest of the body.

Strokes - Damage to a group of nerve cells in the brain as a result of interrupted blood flow; usually caused by a blood clot or blood vessel bursting. Depending on the area of the brain that is damaged, a stroke can cause coma, paralysis, speech problems, and/or dementia.

Synapse - The junction where a signal is transmitted from the axon of one nerve cell to the dendrite of another nerve cell, usually by a neurotransmitter.

Synaptic vesicles - Small sac located in the area of nerve cell axons that contain neurotransmitters. During activity the vescles release their contents at the synapse, and the neurotransmitter stimulate receptors on other cells.


Toxin - A substance that can cause illness, injury or death. Toxins are produced by living organisms.


Vitamins - Various substances found in plants and animals that are required for life-sustaining processes.

Samuel Lewis copyright

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