scholarly journals Unpaired Median Neurones in a Lepidopteran Larva (Antheraea Pernyi): I. Anatomy and Physiology

1988 ◽  
Vol 136 (1) ◽  
pp. 311-332 ◽  
Author(s):  
S. J. BROOKES ◽  
R. G. DE WEEVERS
Keyword(s):  
Nerve Cord ◽  
Action Potentials ◽  
Ventral Nerve Cord ◽  
Intracellular Recordings ◽  
Suboesophageal Ganglion ◽  
Antheraea Pernyi ◽  
Anatomy And Physiology ◽  
Branching Patterns ◽  
The Common ◽  
Synaptic Drive

The anatomy and physiology of two unpaired median neurones (MC1 and MC2) with bilaterally symmetrical axons in abdominal ganglia 3, 4, 5 and 6 of Antheraea pernyi larvae were studied. Intracellular dye filling of MC1 and MC2 revealed that they were distinguishable from all other neurones in the ganglia and that they both had axons projecting out of the ganglia in right and left nerves 1. The two cells were identical in their central anatomy and physiology, but could be distinguished from one another by their peripheral branching patterns. The significance of these patterns was investigated by detailed study of the neural and muscular anatomy of the proleg-bearing segments 3, 4, 5 and 6. The peripheral axons of MC1 and MC2 were exclusively associated with nerve trunks that could be traced to blocks of muscle. Intracellular recordings of the two median cells characteristically showed overshooting soma action potentials that were followed by a long afterhyperpolarization lasting many seconds. Simultaneous recordings from median cells in the same ganglion revealed that MC1 and MC2 shared an excitatory synaptic drive that largely determined their patterns of firing. Recordings from median cells in different ganglia showed that the common synaptic drive was also shared by median cells in different segments. Selective lesions of the ventral nerve cord indicated that the synaptic drive to MC1 and MC2 originated in the suboesophageal ganglion. These cells were similar in anatomy and physiology to the median cells in several other insects.

Electrical interactions between the giant axons of a polychaete worm (Sabella penicillus L.)

1980 ◽  
Vol 84 (1) ◽  
pp. 119-136
Author(s):  
D. Mellon ◽  
J. E. Treherne ◽  
N. J. Lane ◽  
J. B. Harrison ◽  
C. K. Langley
Keyword(s):  
Safety Factor ◽  
Nerve Cord ◽  
Action Potentials ◽  
Divalent Cations ◽  
Muscular Contraction ◽  
The Body ◽  
The Other ◽  
Intracellular Recordings ◽  
Giant Axons ◽  
Other Hand

Intracellular recordings demonstrated a transfer of impulses between the paired giant axons of Sabella, apparently along narrow axonal processes contained within the paired commissures which link the nerve cords in each segment of the body. This transfer appears not to be achieved by chemical transmission, as has been previously supposed. This is indicated by the spread of depolarizing and hyperpolarizing voltage changes between the giant axons, the lack of effects of changes in the concentrations of external divalent cations on impulse transmission and by the effects of hyperpolarization in reducing the amplitude of the depolarizing potential which precedes the action potentials in the follower axon. The ten-to-one attenuation of electronic potentials between the giant axons argues against the possibility of an exclusively passive spread of potential along the axonal processes which link the axons. Observation of impulse traffic within the nerve cord commissures indicates, on the other hand, that transmission is achieved by conduction of action potentials along the axonal processes which link the giant axons. At least four pairs of intact commissures are necessary for inter-axonal transmission, the overall density of current injected at multiple sites on the follower axon being, it is presumed, sufficient to overcome the reduction in safety factor imposed by the geometry of the system in the region where axonal processes join the giant axons. The segmental transmission between the giant axons ensures effective synchronization of impulse traffic initiated in any region of the body and, thus, co-ordination of muscular contraction, during rapid withdrawal responses of the worm.

scholarly journals Synaptic transmission of nervous impulses through the last abdominal ganglion of the cockroach

1937 ◽  
Vol 122 (826) ◽  
pp. 106-118 ◽  
Keyword(s):  
Synaptic Transmission ◽  
Nerve Cord ◽  
Action Potentials ◽  
Ventral Nerve Cord ◽  
Abdominal Ganglion ◽  
Acoustic Stimuli ◽  
Excellent Opportunity ◽  
Random Activity ◽  
Previous Communication

In a previous communication (1936) we have described the response of the cereal nerve of the cricket when the cercus is subjected to acoustic stimuli. In the course of that work we attempted to trace the afferent fibres to their destination by recording from the ventral nerve cord at various levels anterior to the last abdominal ganglion. It was immediately apparent that, while some of the fibres from the acoustically sensitive end-organs of the cercus ran directly through the ganglion and up the cord, others terminated in the ganglion in synaptic relation with a relatively small number of fibres running forwards in the cord and yielding action potentials of considerable magnitude. Contrary to expectation we found that, subject to certain conditions noted below, the random activity in the abdominal nerve cord was never large enough to obscure the wanted signals, and it seemed to us that the preparation offered an excellent opportunity for an examination of the properties of a central nervous synapse. This paper describes the results of this examination.

Physiology of Water Motion Detection in the Medicinal Leech

1981 ◽  
Vol 92 (1) ◽  
pp. 255-275
Author(s):  
W. OTTO FRIESEN
Keyword(s):  
Neuronal Activity ◽  
Water Waves ◽  
Nerve Cord ◽  
Action Potentials ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
Medicinal Leech ◽  
Afferent Input ◽  
Excitatory Input ◽  
Simultaneous Action

1. Neuronal activity resulting from stimulation by water waves occurs in ventral nerve cord-body wall preparations of the medicinal leech, Hirudo medicinalis. In segmental nerves, this activity consists of afferent compound action potentials with graded amplitudes resulting from simultaneous action potentials in many small sensory axons. Afferent input impinging on one segmental ganglion activates neuronal activity along much of the ventral nerve cord. 2. Previously identified tactile mechanoreceptors are insensitive to low-amplitude wave stimulation. Touch-cell impulse activity can be evoked by moderate or strong wave stimulation, but these impulses appear to arise near the cell body, not from the peripheral receptor endings. 3. The transduction sites for wave stimulation are localized at or very near the segmental sensilla. Because of their location and modality the receptors were named ‘sensillar movement receptors’ (SMR). 4. S cells (Rohde's fibre) receive suprathreshold excitatory input during SMR activation without concomitant activity in the tactile mechanoreceptors. 5. The annulus erector motor neurones contralateral to the afferent SMR inflow are inhibited by SMR activation. This inhibition is also observed in ganglia adjacent to the ganglion receiving the afferent input and provides a neuronal basis for reflexive smoothing of the leech body wall. 6. Two neurones in the anterior median packet of segmental ganglia receive powerful synaptic input during SMR activation. One, cell 202, receives 10 mV excitatory potentials while the other, cell 201, receives 10 mV inhibitory potentials.

scholarly journals Distribution of Intersegmental Interneurones That Can Reset the Respiratory Rhythm of the Locust

1989 ◽  
Vol 141 (1) ◽  
pp. 151-176 ◽  
Author(s):  
J. M. RAMIREZ ◽  
K.G. PEARSON
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Rate Increase ◽  
Respiratory Rhythm ◽  
Abdominal Ganglion ◽  
Suboesophageal Ganglion ◽  
Active Components ◽  
Rhythm Generator ◽  
Metathoracic Ganglion ◽  
Staining Techniques

Interneurones in the respiratory rhythm generator of the locust were identified by means of intracellular recording and staining techniques. A description is made of the properties and structures of nine intersegmental neurones which reset the respiratory rhythm when injected with current pulses. All but one of these neurones discharged in phase with expiration. The injection of constant depolarizing current into these interneurones altered the respiratory rate (increase for six, decrease for three). The respiratory rhythm generator extends more posteriorly within the ventral nerve cord than the metathoracic ganglion. In the first fused abdominal ganglion, four individual interneurones were identified descending into the unfused abdominal ganglia. In the first unfused abdominal ganglion an intemeurone which reset the respiratory rhythm was found ascending into the metathoracic ganglion. The respiratory rhythm generator also extends more anteriorly within the ventral nerve cord than the metathoracic ganglion. Two interneurones influencing the respiratory rhythm send their axons from the first fused abdominal ganglion into the meta- and mesothoracic ganglia. One of these directly excited a mesothoracic intemeurone which also influenced the respiratory rhythm when injected with current. In the suboesophageal ganglion another intemeurone was found which, although capable of resetting the respiratory rhythm, was not alway active during respiration. We conclude that the respiratory rhythm generator is distributed over abdominal, thoracic and suboesophageal ganglia. At least one part of the respiratory rhythm generator (in the suboesophageal ganglion) is not always active and can be recruited during vigorous respiration. Thus the number of active components in the respiratory rhythm generator is variable and additional elements can be recruited depending on the behavioural situation.

Extracellular filaments in the perineurium of the florida lobster, Panulirus argus

1987 ◽  
Vol 45 ◽  
pp. 784-785
Author(s):  
Roy J. Baerwald ◽  
Lura C. Williamson
Keyword(s):  
Blood Brain Barrier ◽  
Glial Cells ◽  
Tannic Acid ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Florida Keys ◽  
Panulirus Argus ◽  
Brain Barrier ◽  
Cacodylate Buffer ◽  
Nerve Cords

In arthropods the perineurium surrounds the neuropile, consists of modified glial cells, and is the morphological basis for the blood-brain barrier. The perineurium is surrounded by an acellular neural lamella, sometimes containing scattered collagen-like fibrils. This perineurial-neural lamellar complex is thought to occur ubiquitously throughout the arthropods. This report describes a SEM and TEM study of the sheath surrounding the ventral nerve cord of Panulirus argus.Juvenile P. argus were collected from the Florida Keys and maintained in marine aquaria. Nerve cords were fixed for TEM in Karnovsky's fixative and saturated tannic acid in 0.1 M Na-cacodylate buffer, pH = 7.4; post-fixed in 1.0% OsO4 in the same buffer; dehydrated through a graded series of ethanols; embedded in Epon-Araldite; and examined in a Philips 200 TEM. Nerve cords were fixed for SEM in a similar manner except that tannic acid was not used.

scholarly journals Mutations Affecting Nerve Attachment of Caenorhabditis elegans

Genetics ◽  
2001 ◽  
Vol 157 (4) ◽  
pp. 1611-1622 ◽  
Author(s):  
Go Shioi ◽  
Michinari Shoji ◽  
Masashi Nakamura ◽  
Takeshi Ishihara ◽  
Isao Katsura ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
The Body ◽  
Genetic Loci ◽  
Muscle Attachment ◽  
C Elegans ◽  
Ventral Cord ◽  
Excretory Canal

Abstract Using a pan-neuronal GFP marker, a morphological screen was performed to detect Caenorhabditis elegans larval lethal mutants with severely disorganized major nerve cords. We recovered and characterized 21 mutants that displayed displacement or detachment of the ventral nerve cord from the body wall (Ven: ventral cord abnormal). Six mutations defined three novel genetic loci: ven-1, ven-2, and ven-3. Fifteen mutations proved to be alleles of previously identified muscle attachment/positioning genes, mup-4, mua-1, mua-5, and mua-6. All the mutants also displayed muscle attachment/positioning defects characteristic of mua/mup mutants. The pan-neuronal GFP marker also revealed that mutants of other mua/mup loci, such as mup-1, mup-2, and mua-2, exhibited the Ven defect. The hypodermis, the excretory canal, and the gonad were morphologically abnormal in some of the mutants. The pleiotropic nature of the defects indicates that ven and mua/mup genes are required generally for the maintenance of attachment of tissues to the body wall in C. elegans.

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