acetylcholine: A chemical found in vertebrate neurons that carries information across the synaptic cleft, the space between two nerve cells.

Alzheimers Disease: 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.

axon: The threadlike extensions on a neuron, or nerve cell which conducts nerve impulses.

dementia: Loss of intellectual functions, (such as thinking, remembering, and reasoning) of sufficient severity to interfere within an individual's daily functioning.

dendrite: A long extension of the cytoplasm of a neuron with thin, treelike branches. It receives nerve signals an transmits them to the main body of the cell (called the cyton).

enzymes: Proteins that act as catalysts, speeding the rate at which biochemical reactions proceed but not altering the direction or nature of the reactions.

leukocyte: A pale, nucleated cell that acts as a part of the immune system by destroying invading cells and removing debris.

monocyte: A type of large, round leukocyte that engulfs and breaks down debris and invading cells. Monocytes are formed in bone marrow and have round or kidney-shaped nuclei.

macrophage: A type of large leukocyte that travels in the blood but can leave the bloodstream and enter tissue; like other leukocytes, it protects the body by digesting debris and foreign cells.

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's disease (AD) 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.

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's disease (AD) patients. Upon autopsy, the presence of neuritic plaques and neurofibrillary tangles is used to positively diagnose AD.

neuron: A nerve cell; it receives and conducts electrical impulses from the brain. It consists of a cell body called the cyton, an axon, axon terminals, and dendrites.

Parkinson's disease (parkinsonism): 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's patients have such symptoms as tremors, speech impediments, movement difficulties, and often dementia.

protein: A large molecule composed of one or more chains of amino acids in a specific order; the order is determined by the base sequence of nucleotides in the gene coding for the protein. Proteins are required for the structure, function, and regulation of the bodys cells, tissues, and organs, and each protein has unique functions. Examples are hormones, enzymes, and antibodies.

Jennifer McGilton
mcgilton@u.arizona.edu
6 November 1997
http://student.biology.arizona.edu/ad