Chapter 2 Key Terms and Definitions
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| 302554312 | neuron | The information-processing cell of the nervous system; also called nerve cell. Most neurons use action potentials to send signals over a distance, and all neurons communicate with one another using synaptic transmission. | |
| 302554313 | glial cell | A support cell in the nervous system. Glia are classified into four categories: astrocytes, oligodendroglia, Schwann cells, and microglia. Astrocytes regulate the extracellular environment of the brain, oligodendroglia and Schwann cells provide myelin, and microglia scavenge debris. | |
| 302554314 | histology | The microscopic study of the structure of tissues. | |
| 302554315 | Nissl stain | A class of basic dyes that stain the somata of neurons; named for its discoverer, German histologist Franz Nissl (1860-1919). | |
| 302554316 | cytoarchitecture | The arrangement of neuronal cell bodies in various parts of the brain. | |
| 302554317 | Golgi stain | A method of staining brain tissue that shows neurons and all of their neurites; named for its discoverer, Italian histologist Camillo Golgi (1843-1926). | |
| 302554318 | cell body | The central region of the neuron containing the nucleus; also called soma or perikaryon. | |
| 302554319 | soma | The central region of the neuron containing the nucleus; also called cell body or perikaryon. | |
| 302554320 | perikaryon | The central region of the neuron containing the nucleus; also called soma or cell body. | |
| 302554321 | neurite | A thin tube extending from a neuronal cell body; the two types are axons and dendrites. | |
| 302554322 | axon | A neurite specialized to conduct nerve impulses, or action potentials, normally away from the soma. | |
| 302554323 | dendrite | A neurite specialized to receive synaptic inputs from other neurons. | |
| 302554324 | neuron doctrine | The concept that the neuron is the elementary functional unit of the brain and that neurons communicate with each other by contact, not continuity. | |
| 302554325 | cytosol | The watery fluid inside a cell. | |
| 302554326 | organelle | A membrane-enclosed structure inside a cell; examples are the nucleus, mitochondrion, endoplasmic reticulum, and Golgi apparatus. | |
| 302554327 | cytoplasm | Cellular material contained by the cell membrane, including the organelles but excluding the nucleus. | |
| 302554328 | nucleus | (1) The roughly spherical organelle in a cell body containing the chromosomes. (2) A clearly distinguishable mass of neurons, usually deep in the brain. | |
| 302554329 | chromosome | A structure in the cell nucleus containing a single linear thread of DNA. | |
| 302554330 | DNA (deoxyribonucleic acid) | A double-stranded molecule constructed from four nucleic acids that contains the genetic instructions for a cell. | |
| 302554331 | gene | A unit of heredity; a sequence of DNA that encodes a single polypeptide or protein. | |
| 302554332 | gene expression | The process of transcribing the information from a gene into messenger RNA; a gene is a segment of DNA carrying the instructions for a single protein. | |
| 302554333 | protein | A polymer of amino acids strung together by peptide bonds. | |
| 302554334 | protein synthesis | The assembly of protein molecules in the cell's cytoplasm according to genetic instructions. | |
| 302554335 | mRNA (messenger ribonucleic acid) | A molecule constructed from four nucleic acids that carries the genetic instructions for the assembly of a protein from the nucleus to the cytoplasm. | |
| 302554336 | transcription | The process of synthesizing a messenger RNA molecule according to genetic instructions encoded in DNA. | |
| 302554337 | promoter | A region of DNA that binds RNA polymerase to initiate gene transcription. | |
| 302554338 | transcription factor | A protein that regulates the binding of RNA polymerase to a gene promoter. | |
| 302554339 | RNA splicing | The process by which introns, the regions of a primary RNA transcript that are not used to code protein, are removed. | |
| 302554340 | amino acid | A chemical building block of protein molecules, containing a central carbon atom, an amino group, a carboxyl group, and a variable R group. | |
| 302554341 | translation | The process of synthesizing a protein molecule according to genetic instructions carried by a messenger RNA molecule. | |
| 302554342 | ribosome | A cellular organelle that assembles new proteins from amino acids according to the instructions carried by messenger RNA. | |
| 302554343 | rough endoplasmic reticulum (rough ER) | A membrane-enclosed cellular organelle with ribosomes attached to its outer surface; a site of synthesis for proteins destined to be inserted into membrane or to be enclosed by membrane. | |
| 302554344 | polyribosome | A collection of several ribosomes floating freely in the cytoplasm. | |
| 302554345 | smooth endoplasmic reticulum (smooth ER) | A membrane-enclosed cellular organelle that is heterogeneous and performs different functions in different locations. | |
| 302554346 | Golgi apparatus | An organelle that sorts and chemically modifies proteins that are destined for delivery to different parts of the cell. | |
| 302554347 | mitochondrion | An organelle responsible for cellular respiration. Mitochondria generate adenosine triphosphate using the energy produced by the oxidation of food. | |
| 302554348 | adenosine triphosphate (ATP) | The molecule that is the cell's energy source. The hydrolysis of ATP to produce adenosine diphosphate (ADP) releases energy that fuels most of the biochemical reactions of the neuron. ADP is converted back to ATP in the mitochondria. | |
| 302554349 | neuronal membrane | The barrier, about 5 nm thick, that separates the inside of a nerve cell from the outside; consists of a phospholipid bilayer with proteins embedded in it; encloses the intracellular organelles and vesicles. | |
| 302554350 | cytoskeleton | The internal scaffolding that gives a cell its characteristic shape; consists of microtubules, neurofilaments, and microfilaments. | |
| 302554351 | microtubule | A polymer of the protein tubulin, forming a straight, hollow tube 20 nm in diameter. Microtubules, a component of the cytoskeleton, play an important role in axoplasmic transport. | |
| 302554352 | microfilament | A polymer of the protein actin, forming a braided strand 5 nm in diameter; a component of the cytoskeleton. | |
| 302554353 | neurofilament | A type of intermediate filament found in neurons, 10 nm in diameter; an important component of the neuronal cytoskeleton. | |
| 302554354 | axon hillock | A swelling of the axon where it joins the soma. | |
| 302554355 | axon collateral | A branch of an axon. | |
| 302554356 | axon terminal | The end region of an axon, usually a site of synaptic contact with another cell; also called terminal bouton or presynaptic terminal. | |
| 302554357 | terminal bouton | The end region of an axon, usually a site of synaptic contact with another cell; also called axon terminal. | |
| 302554358 | synapse | The region of contact where a neuron transfers information to another cell. | |
| 302554359 | terminal arbor | Branches at the end of an axon terminating in the same region of the nervous system. | |
| 302554360 | innervation | The provision of synaptic input to a cell or collection of cells. | |
| 302554361 | synaptic vesicle | A membrane-enclosed structure, about 50 nm in diameter, containing neurotransmitter and found at a site of synaptic contact. | |
| 302554362 | synaptic cleft | The region separating the presynaptic and postsynaptic membranes of neurons. | |
| 302554363 | synaptic transmission | The process of transferring information from one cell to another at a synapse. | |
| 302554364 | neurotransmitter | A chemical released by a presynaptic element upon stimulation that activates postsynaptic receptors. | |
| 302554365 | axoplasmic transport | The process of transporting materials down an axon. | |
| 302554366 | anterograde transport | Axoplasmic transport from a neuron's soma to the axon terminal. | |
| 302554367 | retrograde transport | Axoplasmic transport from an axon terminal to the soma. | |
| 302554368 | dendritic tree | All the dendrites of a single neuron. | |
| 302554369 | receptor | (1) A specialized protein that detects chemical signals, such as neurotransmitters, and initiates a cellular response. (2) A specialized cell that detects environmental stimuli and generates neural responses. | |
| 302554370 | dendritic spine | A small sac of membrane that protrudes from the dendrites of some cells and receives synaptic input. | |
| 302554371 | unipolar neuron | A neuron with a single neurite. | |
| 302554372 | bipolar neuron | A neuron with two neurites. | |
| 302554373 | multipolar neuron | A neuron with three or more neurites. | |
| 302554374 | stellate cell | A neuron characterized by a radial, starlike distribution of dendrites. | |
| 302554375 | pyramidal cell | A neuron characterized by a pyramid-shaped cell body and elongated dendritic tree; found in the cerebral cortex. | |
| 302554376 | spiny neuron | A neuron with dendritic spines. | |
| 302554377 | aspinous neuron | A neuron lacking dendritic spines. | |
| 302554378 | primary sensory neuron | A neuron specialized to detect environmental signals at the body's sensory surfaces. | |
| 302554379 | motor neuron | A neuron that synapses on a muscle cell and causes muscle contraction. | |
| 302554380 | interneuron | Any neuron that is not a sensory or motor neuron; also describes a CNS neuron whose axon does not leave the structure in which it resides. | |
| 302554381 | astrocyte | A glial cell in the brain that supports neurons and regulates the extracellular ionic and chemical environment. | |
| 302554382 | oligodendroglial cell | A glial cell that provides myelin in the central nervous system. | |
| 302554383 | Schwann cell | A glial cell that provides myelin in the peripheral nervous system. | |
| 302554384 | myelin | A membranous wrapping, or sheath, around axons provided by oligodendroglia in the central nervous system and Schwann cells in the peripheral nervous system. | |
| 302554385 | node of Ranvier | A space between two consecutive myelin sheaths where an axon comes in contact with the extracellular fluid. | |
| 302554386 | ependymal cell | A type of glial cell that provides the lining of the brain's ventricular system. | |
| 302554387 | microglial cell | A type of cell that functions as a phagocyte in the nervous system to remove debris left by dead or dying neurons and glia. |
