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Amacrine cell. Local interneuron lacking axon.
Antennal lobe. Major (possibly unique) deutocerebral processing center supplied by terminals of olfactory receptors that are situated in the third segment of the antenna and from the maxillary palps.
Antennal mechanosensory and motor center. Mechanosensory neurons reach this center mainly from the first and second (Johnston's organ) antennal segments.
Brain. See supra- and suboesophageal ganglia.
Commissure. A broad band of axons connecting the same neuropils each side of the brain.
Corpora allata. with C. cardiaca form the retrocerebral complex, a neurosecretory organ.
Corpora cardiaca.
Corpora pedunculata, see mushroom bodies.
Cartridge. Unit structure of the lamina neuropil. See also column.
Calyx. Neuropil containing the dendrites of mushroom body intrinsic cells (Kenyon cells) and receiving sensory interneuron afferents, mainly from the antennal lobes.
Central body complex. Complex of neuropils comprising the protocerebral bridge, superior arch, fan-shaped body, ellipsoid body, and noduli. Some authors include the ventral bodies as members of this complex.
Column. Generic term for the unit of optic neuropil, such as a lamina cartridge, corresponding with an overlying ommatidium in the compound eye, whence columnar neurons.
Columnar neurons. Neurons of the optic lobe with a representative in each column, or in particular subsets of columns, having a neurite orientated predominantly in a direction perpendicular to the neuropil surface.
Chiasma. A crossed projection of axons reversing their linear order between two neuropils. see Optic Chiasma.
Decussation. A tract of nerve fibers, passing between neuropils on opposite sides of the nervous system, organized such that the linear order of axons on one side is reversed on the other.
Dendrite. The region of a neuron receiving inputs from other neurons, typically a slender neurite, often branched. In insect neurons, this is often not a clear designation and often presynaptic sites co-extend with postsynaptic ones.
Dendritric tree. The arborization of dendrites, defined by the number, position, branching structure, density and stratification of its branches.
Dense body. Synaptic ribbon at neuromuscular junction.
Fan-shaped body. Region of the central body of the insect brain.
Fascicle. A slender bundle of axons linking one neuropil to another.
Ganglion (pl. ganglia) e.g thoracic ganglion. Any of a number of aggregations of neurons, glial cells and their processes, surrounded by a glial cell and connective tissue sheath.
Ganglion cell. The neuron of a ganglion.
Glomerulus. Roundish subunit structure of a neuropil, often ensheathed by glial lamellae. Also, unit structure of the antennal lobe.
Identifiable neuron, uniquely. Cells that can be recognized repeatedly and individually from animal to animal of a particular species or, of related forms of a taxonomic group, or characterizing a specific part of the CNS.
Interneuron. A neuron that is neither a sensory receptor nor a motorneuron. See: Local interneuron and Projection neuron.
Lamina (ganglionaris). First optic neuropil.
Lobula. Third optic neuropil. The final site of visual processing in the optic lobe. In holometabolous insects this neuropil is usually divided into a lobula and (posteriorly) a lobula plate.
Local interneurons. Small interneurons that have similarly shaped dendritic fields and have axons that extend only locally within a neuropil.
Medulla. Second optic neuropil, the major processing center for the visual pathway of the compound eye.
Mushroom bodies. Paired neuropils, thought to be crucial to olfactory associative learning and memory. Mushroom body neuropils are divided into calyces, pedunculus, and its subsequent lobes. In Drosophila these are the alpha, beta, and gamma lobes.
Neurite. One of the processes or extensions of a neuron, axon or dendrite or cell body fiber.
Neuropil. A delineated assemblage of processes from a population of neurons, the somata of which usually occupy the surrounding or nearby rind. A neuropil is the location of synaptic contacts between neurons. Typically the neuropil is organized into laminae or other defined architectures --- such as glomeruli --- with fiber pathways connecting between adjacent neuropils.
Optic Chiasma. The projection of axons between the lamina and medulla (1st optric chiasma) or between the medulla and lobula (2nd optic chiasma). The linear order of axons along each horizontal row of retinotopic columns (see optic cartridges) is reversed by the chiasma.
Optic lobe. Visual processing centers underlying the compound eyes.
Pars intercerebralis. A medial cleft or depression dividing the left and right protocerebrum and containing numerous large and small somata of neurosecretory and neuromodulatory neurons.
Perikaryon (pl. perikarya). The cytoplasm of the soma of a neuron, surrounding the nucleus.
Presynaptic ribbon: see Synaptic ribbon. Organelle at the input site of a synapse, the presumed structure for vesicle exocytosis, comprising a central pedestal but often with several components (e.g. a platform in recent groups of Diptera).
Projection neuron. A neuron that links one neuropil to one or more others.
Protocerebrum. Most anterior of the broad embryonic divisions of the insect CNS; thought to represent the first preoral segment of the brain. The protocerebrum comprises many discrete neuropil regions including the central body complex and mushroom bodies.
Soma. The cell body of a neuron.
Suboesophageal ganglion. Post-oral neuropils of the brain comprising three fused ganglia beneath the oesophagus.
Supraoesophageal ganglion. Pre-oral neuropils of the brain comprising three fused ganglia (protocerebrum, deutocerebrum, and tritocerebrum) in the head, above the oesophagus.
Synapse. Structural contact that is the site of transmission between neurons, identified by a presynaptic ribbon and synaptic vesicles as the input element and one or (usually) more postsynaptic elements with various specializations (membrane densities, cisternae, etc.).
Synaptic ribbon. An electron-dense presynaptic organelle found at that site of synaptic transmission and the presumed site of vesicle exocytosis, see also dense body. Named by comparison with ribbon synapses of vertebrate receptors.
Terminal. Output region of a neuron, generally presynaptic but in insects often also locally postsynaptic. Typically containing large numbers of mitochondria in addition to presynaptic organelles.
Tract. A group of axons linking two or more neuropils and having a common origin, termination.
Visual neuropils (not ganglia). Processing neuropils of the optic lobe. A former usage, still occasionally seen, is for optic ganglia.


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