antioxidant An enzyme or chemical that inactivates reactive oxygen species.

apoptosis A form of programmed cell death that has a characteristic structural appearance and occurs through the activation of intrinsic cell death pathways.

apoptosis-necrosis continuum The concept that neuronal cell death can occur as typical apoptosis, typical necrosis, or as intermediates or hybrids of cell death with varying, overlapping contributions of apoptosis and necrosis.

astroglia Glial cells in the central nervous system that have long radial processes that ensheathe neurons and synaptic complexes.

Astroglia regulate the extracellular chemical and ionic environment and secrete peptides, growth factors, cytokines, and chemokines.

axotomy Experimental injury to the neuronal axon (or bundles of axons) by transection, avulsion, or trauma.

central nervous system The brain and spinal cord.

death protein A protein that regulates programmed cell death.

excitotoxicity A neurotoxic process that is mediated by excessive activation of excitatory glutamate receptors.

experimental neuropathology The study of neurodegeneration in animal or cell culture model systems.

glial cell Nonneuronal cell in the nervous system (e.g., astrocyte, oligodendrocyte, microglial cell, Schwann cell).

glutamate receptor A family of cell membrane proteins located on neurons and glia that bind glutamate or related chemicals, causing depolarization by ionic conductance or activation of enzymes resulting in the production or release of intracellular second messengers.

microglia The resident small phagocytic cells of the brain and spinal cord that are related to the mononuclear phagocyte lineage and function as immune accessory cells that secrete cytokines and chemokines.

mutation Change in the DNA nucleotide sequence of a gene.

necrosis A form of cell death that has a characteristic structural appearance and occurs through the failure of homeostatic mechanisms (e.g., energy production, cell volume).

neurotransmitter Signaling molecule secreted by the presynaptic terminal of a neuron at chemical synapses to relay a signal to a postsynaptic neuron (e.g., glutamate).

NMDA receptor A type of ion channel glutamate receptor that controls neuronal excitation and is very important for synaptic plasticity. It regulates intracellular Ca2 + . Overactivation of NMDA receptors causes excitotoxic neuronal death.

oligodendroglia Glial cells that provide myelin sheaths for axons within the CNS and secrete peptide growth factors.

programmed cell death A form of cell death that is brought about by intrinsic cellular pathways involving specific death proteins.

Encyclopedia of the Human Brain Volume 3

Copyright 2002, Elsevier Science (USA).

All rights reserved.

reactive oxygen species An oxygen molecule containing an odd number of electrons rendering it chemically reactive due to an open bond (e.g., superoxide, hydroxyl radical, nitric oxide).

stem cell Relatively undifferentiated cell that can divide into daughter cells that can undergo terminal differentiation into particular cell types (e.g., neurons).

target deprivation The removal or ablation of a brain region or peripheral tissue that is the site with which a group of neurons connects.

Neurodegeneration is the pathology of neurons instigated by an acute insult or a chronic perturbation in cell function. The process of neurodegeneration can be rapid or it can be slow and progressive, and it can result in neuronal loss and neuronal dysfunction with neurological consequences. Acute neurodegeneration is caused by cerebral ischemia (stroke and cardiac arrest), toxins, and trauma. Chronic neurodegeneration is caused by diseases such as Alzheimer's disease, amyotrophic lateral sclerosis, Huntington's disease, and Parkinson's disease. In different neurological disorders, different groups of neurons are selectively vulnerable to the molecular pathology of the degenerative process. The basis for this selective vulnerability may be intrinsic to the different groups of neurons. Models of experimental neuropathology are essential for discovering the mechanisms for selective neuronal vulnerability to injury and neurodegenerative disease.

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