Biomaterial Database

Morphological and electrophysiological properties of giant interneurons during the postembryonic development of the cockroach CNS. 1983

Y Yarom, and M E Spira

The giant interneurons (GIN) of the central nervous system of the cockroach undergo two major physiological changes during the postembryonic development period: (A) a gradual decrease in the safety factor for action potential propagation across the GIN in the metathoracic ganglion (T3); and (B) a marked decrease in the number of afferent pathways innervating the GIN in T3 (Spira and Yarom). Analysis of the morphological structure of the GINs, by intracellular injection of cobalt ions and by cross-sections prepared for light and electron microscope, reveals that despite the extensive growth of the GINs during the postembryonic developmental period, the main structural outline of the fibers is not altered. In adult preparations, however, the GIN diameter narrows 25-26% in ganglion T3, while in early nymphal stages the reduction is only 8-10%. The difference in the extent of narrowing of the fibers in adult and nymphal stages is the major factor that accounts for the development of a low safety factor region for impulse propagation across T3. Analysis of the passive membrane properties of the GIN reveals that the electrotonic length of the GIN segment in T3 is identical in adult and nymphal stages. It is concluded that the functional disappearance of afferents innervating the GINs in T3 is a consequence of decreased transmission efficacy along the afferent pathways.

UI	MeSH Term	Description	Entries
D007395	Interneurons	Most generally any NEURONS which are not motor or sensory. Interneurons may also refer to neurons whose AXONS remain within a particular brain region in contrast to projection neurons, which have axons projecting to other brain regions.	Intercalated Neurons,Intercalated Neuron,Interneuron,Neuron, Intercalated,Neurons, Intercalated
D007814	Larva	Wormlike or grublike stage, following the egg in the life cycle of insects, worms, and other metamorphosing animals.	Maggots,Tadpoles,Larvae,Maggot,Tadpole
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D009435	Synaptic Transmission	The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.	Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
D010526	Periplaneta	A genus in the family Blattidae containing several species, the most common being P. americana, the American cockroach.	Periplaneta americana,American Cockroach,American Cockroaches,American Cockroache,American Cockroachs,Cockroach, American,Cockroache, American,Cockroaches, American,Cockroachs, American,Periplaneta americanas,Periplanetas,americana, Periplaneta
D002490	Central Nervous System	The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges.	Cerebrospinal Axis,Axi, Cerebrospinal,Axis, Cerebrospinal,Central Nervous Systems,Cerebrospinal Axi,Nervous System, Central,Nervous Systems, Central,Systems, Central Nervous
D003058	Cockroaches	Insects of the order Dictyoptera comprising several families including Blaberidae, BLATTELLIDAE, Blattidae (containing the American cockroach PERIPLANETA americana), Cryptocercidae, and Polyphagidae.	Blaberidae,Blattaria,Blattidae,Blattodea,Cryptocercidae,Dictyoptera,Polyphagidae,Cockroach,Blattarias,Blattodeas,Cockroache,Cockroachs,Dictyopteras
D005724	Ganglia	Clusters of multipolar neurons surrounded by a capsule of loosely organized CONNECTIVE TISSUE located outside the CENTRAL NERVOUS SYSTEM.
D000344	Afferent Pathways	Nerve structures through which impulses are conducted from a peripheral part toward a nerve center.	Afferent Pathway,Pathway, Afferent,Pathways, Afferent