Structure and organization of the nervous system in the actinotroch larva of Phoronis vancouverensis

1990 ◽  
Vol 327 (1244) ◽  
pp. 655-685 ◽  
Keyword(s):  
Nervous System ◽  
Nerve Cell ◽  
Central Element ◽  
Neuromuscular Control ◽  
The Body ◽  
Oral Feeding ◽  
Apical Organ ◽  
Morphological Evidence ◽  
Ciliary Band ◽  
Phylogenetic Implications

The nervous system of the earliest functional stage of the actinotroch larva of Phoronis vancouverensis is described based on ultrastructural surveys and three-dimensional reconstructions, including serial reconstructions of selected parts of the system. The central element and main source of fibres in the system is the apical organ. Nerve cell bodies were found here and in the surrounding apical epithelium, but nowhere else in the body. Given the limitations of the methods used, the presence of nerve cell bodies elsewhere in the body cannot be ruled out, but based on this work and a recent study by A. Hay-Schmidt of whole larvae, it seems unlikely they occur in any numbers. The larval nervous system is thus highly centralized, an advanced and rather specialized feature in comparison with some other larval types, specifically those of primitive spiralia and echinoderms, in which nerve cell bodies are more widely distributed in the larval epithelium. The largest single nerve in the body is the primary hood nerve, which runs around the pre-oral hood slightly back from its margin. The nerve is a compact, well-defined tract of approximately 40 fibres, with an investment of glial-like accessory cells. A second set of smaller, accessory nerves run parallel to the primary nerve between it and the hood margin. The hood nerves all join at the base of the hood on either side of the mouth to form a pair of adoral nerve centres. A number of small nerves cross the hood from the apical organ to the hood nerves. Three of these are large enough to be considered major nerves: one is medial and connects to the centre of the hood margin, the other two are dorsolateral and connect to the adoral nerve centres. Fibre tracings, which show the distribution of vesicle-filled terminals and varicosities, suggest the hood nerves are mainly involved in neuromuscular control, specifically, in lifting the hood. This involves the stimulation, in sequence, of the radial and circular hood muscles by the primary and accessory hood nerves, respectively. Cells at the hood margin are organized somewhat in the fashion of a conventional ciliary band, but there is no obvious morphological evidence that any of the hood nerves are involved in neurociliary control. A diffuse plexus of small nerves connects the above apical structures to the nerves supplying the tentacles. There are two main tentacle nerves, the primary tentacle nerve, which runs along the upper, oral margin of the tentacular ciliary band, and a smaller accessory nerve, which arises as a branch from the primary nerve, and runs along the lower, aboral margin of the band. There is also a row of uniciliate sensory receptor cells at the oral margin of the band. Each cell has a basal process ending in a vesicle-filled terminal that abuts fibres in the upper tentacle nerve, and forms junctions with them. The cells themselves produce no other fibres. They appear to be mechanosensory, and are probably involved in initiating the hood lift response, which can be triggered by touching the top surface of the tentacles. Additional large, vesicle-filled terminals branch from the fibres in the primary tentacle nerve. Their positions suggest a neurociliary function. The accessory tentacle nerve is associated mainly with muscle cells. A series of small nerves, which probably arise as branches from the larger tentacle nerves, supply the region below the tentacles, later the site of the telotroch. The comparative and phylogenetic implications of the above are discussed. Phoronids are generally interpreted as being intermediate between deuterostomes and protostomes, with a curious mixture of characteristics of both groups. Phoronids are probably only distantly related to spiralian protostomes, but they are, strictly speaking, protostomes, and their larvae resemble the trochophore-type larvae of spiralia in many respects. Regarding ciliary band substructure and patterns of innervation, the actinotroch possesses too few features that are clearly primitive to support a detailed comparison with spiralian larvae, but the pre-oral hood band shows a sufficient number of prototroch-like features, to suggest the hood band and prototroch could be homologous. There is evidence for parallel evolution, in the two groups, of an increasingly centralized nervous system that provides improved effector control via nerve cells located in and around the apical organ. No evidence was obtained to support suggested homologies between the post-oral band of the actinotroch and circumoral or post-oral feeding bands in deuterostome larvae. The two appear, in fact, to be quite dissimilar in terms of their innervation. The results thus support conventional interpretations of the relationship between phoronids and other major groups.

The nervous system and ciliary band of Müller’s larva

1982 ◽  
Vol 217 (1206) ◽  
pp. 37-58 ◽  
Keyword(s):  
Nervous System ◽  
Basement Membrane ◽  
The Body ◽  
Sensory Cells ◽  
Ciliary Band ◽  
Electron Microscopical Level ◽  
The Central Nervous System ◽  
Electron Microscopical ◽  
Pass Through ◽  
The Right

The newly hatched Müller’s larva of the polyclad Pseudoceros canadensis is described at the electron microscopical level with attention to the arrangement and innervation of the ciliary band and the organization of the larval nervous system. Distinctive ultrastructural features allow the trochal cells of the band to be distinguished from general epithelium of the body surface and the specialized oral field epithelium. The band comprises a ventral and a dorsal marginal loop that run along the margins of the six projecting lobes of the larva, and a suboral plate that forms a bridge between these behind the mouth. These three components are joined asymmetrically to form a single, but discontinuous, band: on the left the ventral loop and suboral plate are joined, but these fail to connect with the dorsal loop; on the right it is the ventral and dorsal loops that join, but there is no connection between these and the suboral plate. A system of intraepithelial nerves is associated with the ciliary band, the largest nerves being those in the ventrolateral lobes and the intraepithelial commissure that connects these across the oral field. The system is truly peripheral: it lies outside the basement membrane and is separated by it from the central nervous system, which at this stage comprises a brain and four radiating nerve cords. The peripheral and central nervous systems are in direct contact only at two points, located just behind the ventrolateral lobes on either side of the larva, where a few neurites pass through the basement membrane from one system to the other. The neurites of the peripheral system arise mainly from bipolar sensory cells located in the ciliary band. These are concentrated along the ventrolateral lobes, and their projecting cilia face incoming water currents. Observations on larval swimming behaviour do not, however, suggest any obvious function for these cells. The ciliary band is thus organized as a self-contained unit supplying its own innervation. Other primitive invertebrate larvae have ciliary bands that are similar to some extent in their organization and ultra­structure. This, added to what is already known about Müller’s larva, supports the idea that it is primitive and is closely related to at least several other larval types, but it is not clear how the overall arrangement of the band in Müller’s larva as described here relates to what is seen in other larvae. Several ways in which the pattern might have originated from simpler patterns in hypothetical ancestral forms are, however, discussed.

Immunocytochemical localization of serotonin (5-HT) in the nervous system of the hydatid organism, Echinococcus granulosus (Cestoda, Cyclophyllidea)

Parasitology ◽  
1994 ◽  
Vol 109 (2) ◽  
pp. 233-241 ◽  
Author(s):  
D. J. A. Brownlee ◽  
I. Fairweather ◽  
C. F. Johnston ◽  
M. T. Rogan
Keyword(s):  
Nervous System ◽  
Nerve Cell ◽  
Echinococcus Granulosus ◽  
Large Population ◽  
The Body ◽  
Confocal Scanning Laser Microscopy ◽  
Nerve Fibres ◽  
Confocal Scanning Laser ◽  
Serotonin Immunoreactivity ◽  
Nerve Cords

SUMMARYThe localization and distribution of the serotoninergic components of the nervous system in the hydatid organism, Echinococcus granulosus, were determined by immunocytochemical techniques in conjunction with confocal scanning laser microscopy (CSLM). The distribution of serotonin immunoreactivity (IR) paralleled that previously described for cholinesterase activity, although it was more widespread. Nerve cell bodies and nerve fibres immunoreactive for 5-HT were present throughout the central nervous system (CNS), occurring in the paired lateral, posterior lateral and rostellar ganglia, their connecting commissures and nerve rings in the scolex and in the ten longitudinal nerve cords that run posteriorly throughout the body of the worm. A large population of nerve cell bodies was associated with the lateral nerve cords. In the peripheral nervous system (PNS), immunoreactive nerve fibres occurred in well-developed nerve plexuses innervating the somatic musculature and the musculature of the rostellum and suckers. The genital atrium and associated reproductive ducts were richly innervated with serotoninergic nerve cell bodies and nerve fibres.

Memoirs: The Anatomical Organization of the Nervous System of Enteropneusta

1945 ◽  
Vol s2-86 (341) ◽  
pp. 55-111
Author(s):  
THEODORE HOLMES BULLOCK
Keyword(s):  
Nervous System ◽  
Nerve Cell ◽  
Nervous Tissue ◽  
Sensory Nerve ◽  
Dorsal Side ◽  
The Body ◽  
Sensory Cells ◽  
Nerve Fibres ◽  
Primitive Form ◽  
Low Order

1. Results of a detailed study of the nervous system of Saccoglossus pusillus, with comparative material of about two dozen other species of Enteropneusta, are presented. 2. The primary feature of the enteropneust nervous system is its position within the superficial epithelium. Pertinent relations with non-nervous elements of the epithelium are described. The indifferent, ciliated cells elaborate supporting fibres in those regions where the epithelium is well developed and nervous tissue is concentrated. Such cells are considered to represent neuroglia in its most primitive form. The fibres appear in places to be continuous with the ciliary rootlet cones. 3. Nerve-cells are distributed diffusely in all the epithelia of the body, with certain exceptions such as the intestine, gills, coelomoducts, and the non-glandular areas of the abdomen of some forms. Both sensory and connecting and possibly also motor neurons occur here; but the sensory cells greatly predominate, often outnumbering all other epithelial cell-types combined. However, but one morphologic type of sensory cell--a true primary sense-cell--and no sense organs seem to be present. The thesis of Hanström is borne out that the low order of complexity of the nervous system as a whole is correlated with a low order of development of sensory structures. This in turn is correlated with a sluggish bottom living habit of life. 4. The nervous tissue is shown to be conspicuously undifferentiated. All nerve-cell processes are alike and resemble the most primitive nerve-fibres. A single exception is formed by the giant nerve-cell fibres, of which a few dozen exist in the nerve-cords. The absence of strata, tracts, and special neuropile-like regions as well as of elaborate nerve endings, ganglia, nerves, and ‘nuclei’, is impressive. Following the neurologic principle that complexity of function is reflected in complexity of structure, this is taken to mean a low degree of functional specialization. 5. Indications of several kinds agree in suggesting that the relations between neurons are something other than proto plasmic continuity. In the sense that nerve-fibres from different neurons are discontinuous the enteropneust nervous system is tentatively to be regarded as synaptic. Experimentally, however, the plexus has been shown to function as a nerve-net. It is proposed that such physiologic behaviour be taken to indicate a net in the sense of diffuse conduction, but that it does not predicate anatomical continuity of the fibres of the net. Such a picture requires the assumption of unpolarized synapses and the facts derived from the present organisms are taken to be evidence for this assumption. 6. Other primitive characters are described. The synapses are unlocalized, being scattered throughout the plexus. No special structural modifications have been developed at the synaptic endings. Connexions with the interior across the limiting membrane, heretofore unknown, are astonishingly difficult to demonstrate, but they must be assumed to exist and evidence is accumulated that they are diffuse. The widely scattered sense-cells, synapses, ganglion cells, and connexions with the interior are correlated with, and account for, the experimentally demonstrated autonomy of small pieces of the body-wall. 7. The general plexus is locally thickened and modified (1) in the cords of the mid-dorsal and mid-ventral lines of the trunk, (2) circularly around the junction of the collar and trunk, (3) through the dorsal collar coelom as an internal, primitively hollow, medullary strand, and (4) on the dorsal side of the peduncle. These are primarily conduction paths and are only secondarily important as ganglionic or modifying regions. The ventral cord in the trunk is shown to be larger and more important than the dorsal. In the sense of an organ which is involved in all reflexes, which contains all the intermediate neurons, and to which pass all sensory nerve-fibres, the balanoglossid has no central nervous system. 8. Internal to the limiting membrane no concentrations of nervous tissue are known with certainty to occur. No nerves, ganglia, or layers have been developed. As yet inadequately demonstrated, the internal nervous sytem can at most be only a sparse and diffuse system of cells and fibres communicating across the limiting membrane with the superficial plexus, at the least nothing but motor axons passing from cell-bodies in the integument inwards to the muscles. 9. The histologic evidence supports the previously demonstrated physiologic picture placing the Hemichordata in respect to the level of complexity of the nervous system below all other groups of animals with nervous systems except the coelenterates and ctenophores. No evidence is adduced that this primitiveness is secondary rather than original. In numerous histologic respects the enteropneust nervous system resembles that of Echinodermata and Phoronidea, but is simpler than either. 10. The chordate affinities of the balanoglossids are here accepted. But the strength of the argument from the nervous system is considered to have been overdrawn. No aspect of the general picture of primitiveness now demonstrated is, however, considered to argue against these affinities.

Neuron-glia relationship during the early postembryonic development of the nervous system in some oligochaetes

1978 ◽  
Vol 36 (2) ◽  
pp. 600-601
Author(s):  
Wiktor Djaczenko ◽  
Carmen Calenda Cimmino
Keyword(s):  
Nervous System ◽  
Glial Cells ◽  
Early Period ◽  
Postembryonic Development ◽  
Ruthenium Red ◽  
The Body ◽  
Tubifex Tubifex ◽  
Growth Stages ◽  
Cell Processes ◽  
Cytoplasmic Processes

The simplicity of the developing nervous system of oligochaetes makes of it an excellent model for the study of the relationships between glia and neurons. In the present communication we describe the relationships between glia and neurons in the early periods of post-embryonic development in some species of oligochaetes.Tubifex tubifex (Mull. ) and Octolasium complanatum (Dugès) specimens starting from 0. 3 mm of body length were collected from laboratory cultures divided into three groups each group fixed separately by one of the following methods: (a) 4% glutaraldehyde and 1% acrolein fixation followed by osmium tetroxide, (b) TAPO technique, (c) ruthenium red method.Our observations concern the early period of the postembryonic development of the nervous system in oligochaetes. During this period neurons occupy fixed positions in the body the only observable change being the increase in volume of their perikaryons. Perikaryons of glial cells were located at some distance from neurons. Long cytoplasmic processes of glial cells tended to approach the neurons. The superimposed contours of glial cell processes designed from electron micrographs, taken at the same magnification, typical for five successive growth stages of the nervous system of Octolasium complanatum are shown in Fig. 1. Neuron is designed symbolically to facilitate the understanding of the kinetics of the growth process.

Characteristics of the dynamics of the central nervous system and att ention function in workers of shoe production

2020 ◽  
pp. 64-68
Author(s):  
F. L. Azizova ◽  
U. A. Boltaboev
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Women Workers ◽  
Functional State ◽  
The Body ◽  
Conflict Of Interests ◽  
Professional Groups ◽  
Universal Device ◽  
The Central Nervous System ◽  
Working Day

The features of production factors established at the main workplaces of shoe production are considered. The materials on the results of the study of the functional state of the central nervous system of women workers of shoe production in the dynamics of the working day are presented. The level of functional state of the central nervous system was determined by the speed of visual and auditory-motor reactions, installed using the universal device chronoreflexometer. It was revealed that in the body of workers of shoe production there is an early development of inhibitory processes in the central nervous system, which is expressed in an increase in the number of errors when performing tasks on proofreading tables. It was found that the most pronounced shift s in auditory-motor responses were observed in professional groups, where higher levels of noise were registered in the workplace. The correlation analysis showed a close direct relationship between the growth of mistakes made in the market and the decrease in production. An increase in the time spent on the task indicates the occurrence and growth of production fatigue.Funding. The study had no funding.Conflict of interests. The authors declare no conflict of interests.

Neurophysiological and morphological effects in the post-exposure vibration period during experimental modeling

2019 ◽  
pp. 284-290
Author(s):  
Natalya L. Yakimova ◽  
Vladimir A. Pankov ◽  
Aleksandr V. Lizarev ◽  
Viktor S. Rukavishnikov ◽  
Marina V. Kuleshova ◽  
...  
Keyword(s):  
Nervous System ◽  
Evoked Potentials ◽  
Experimental Model ◽  
Visual Evoked Potentials ◽  
The Body ◽  
Behavioral Activity ◽  
Contact Period ◽  
Vibration Exposure ◽  
Visual Evoked

Introduction. Vibration disease continues to occupy one of the leading places in the structure of professional pathology. In workers after the termination of contact with vibration generalization and progression of violations in an organism is noted. The pathogenetic mechanisms of the progredient course of disturbances in the nervous system in the post-contact period of vibration exposure remain insufficiently studied.The aim of the study was to test an experimental model of vibration exposure to assess the neurophysiological and morphological effects of vibration in rats in the dynamics of the post-contact period.Materials and methods. The work was performed on 168 white male outbred rats aged 3 months weighing 180–260 g. The vibration effect was carried out on a 40 Hz vibrating table for 60 days 5 times a week for 4 hours a day. Examination of animals was performed after the end of the physical factor, on the 30th, 60th and 120th day of the post-contact period. To assess the long-term neurophysiological and morphofunctional effects of vibration in rats, we used indicators of behavioral reactions, bioelectric activity of the somatosensory zone of the cerebral cortex, somatosensory and visual evoked potentials, parameters of muscle response, morphological parameters of nervous tissue.Results. In the dynamics of the post-contact period observed the preservation of violations of tentatively research, motor and emotional components of behavior. In the Central nervous system instability of activity of rhythms of an electroencephalogram, decrease in amplitude of visual evoked potentials, lengthening of latency of somatosensory evoked potentials, decrease in total number of normal neurons and astroglia is established. In the peripheral nervous system remained changes in indicators: increasing duration and latency, reducing the amplitude of the neuromuscular response.Conclusions: The experimental model allows us to study the long-term neurophysiological and morphological effects of vibration on the body. The formation and preservation of changes in behavioral activity, neurophysiological and morphological effects of vibration from the 30th to the 120th day of the post-contact period were confirmed.

Emotional processing and the autonomic nervous system: a comprehensive meta-analytic investigation

2018 ◽  
Author(s):  
Pedro Silva Moreira ◽  
Pedro Chaves ◽  
Nuno Dias ◽  
Patrício Costa ◽  
Pedro Rocha Almeida
Keyword(s):  
Nervous System ◽  
Autonomic Nervous System ◽  
Skin Conductance ◽  
Emotional Processing ◽  
Skin Conductance Level ◽  
The Body ◽  
Analytic Investigation ◽  
Physiological Basis ◽  
Autonomic Nervous ◽  
Conductance Level

Background: The search for autonomic correlates of emotional processing has been a matter of interest for the scientific community with the goal of identifying the physiological basis of emotion. Despite an extensive state-of-the-art exploring the correlates of emotion, there is no absolute consensus regarding how the body processes an affective state.Objectives: In this work, we aimed to aggregate the literature of psychophysiological studies in the context of emotional induction. Methods: For this purpose, we conducted a systematic review of the literature and a meta-analytic investigation, comparing different measures from the electrodermal, cardiovascular, respiratory and facial systems across emotional categories/dimensions. Two-hundred and ninety-one studies met the inclusion criteria and were quantitatively pooled in random-effects meta-analytic modelling. Results: Heart rate and skin conductance level were the most reported psychophysiological measures. Overall, there was a negligible differentiation between emotional categories with respect to the pooled estimates. Of note, considerable amount of between-studies’ heterogeneity was found in the meta-analytic aggregation. Self-reported ratings of emotional arousal were found to be associated with specific autonomic-nervous system (ANS) indices, particularly with the variation of the skin conductance level. Conclusions: Despite this clear association, there is still a considerable amount of unexplained variability that raises the need for more fine-grained analysis to be implemented in future research in this field.

Neural Stem Cells to Glial Cells an Important Factor for Brain Injury

2020 ◽  
Author(s):  
Prithiv K R Kumar
Keyword(s):  
Stem Cells ◽  
Central Nervous System ◽  
Nervous System ◽  
Neural Stem Cells ◽  
Glial Cells ◽  
Brain Injuries ◽  
The Body ◽  
The Central Nervous System ◽  
Near Future

Stem cells have the capacity to differentiate into any type of cell or organ. Stems cell originate from any part of the body, including the brain. Brain cells or rather neural stem cells have the capacitive advantage of differentiating into the central nervous system leading to the formation of neurons and glial cells. Neural stem cells should have a source by editing DNA, or by mixings chemical enzymes of iPSCs. By this method, a limitless number of neuron stem cells can be obtained. Increase in supply of NSCs help in repairing glial cells which in-turn heal the central nervous system. Generally, brain injuries cause motor and sensory deficits leading to stroke. With all trials from novel therapeutic methods to enhanced rehabilitation time, the economy and quality of life is suppressed. Only PSCs have proven effective for grafting cells into NSCs. Neurons derived from stem cells is the only challenge that limits in-vitro usage in the near future.

Therapeutic Potential of Agonists and Antagonists of A1, A2a, A2b and A3 Adenosine Receptors

2019 ◽  
Vol 25 (26) ◽  
pp. 2892-2905 ◽  
Author(s):  
Sumit Jamwal ◽  
Ashish Mittal ◽  
Puneet Kumar ◽  
Dana M. Alhayani ◽  
Amal Al-Aboudi
Keyword(s):  
Nervous System ◽  
Therapeutic Potential ◽  
The Body ◽  
Membrane Receptors ◽  
Physiological Importance ◽  
Physiological Processes ◽  
Central Nervous Systems ◽  
Energy Consuming ◽  
Metabolic Dysfunctions ◽  
G Protein Coupled

Adenosine is a naturally occurring nucleoside and an essential component of the energy production and utilization systems of the body. Adenosine is formed by the degradation of adenosine-triphosphate (ATP) during energy-consuming processes. Adenosine regulates numerous physiological processes through activation of four subtypes of G-protein coupled membrane receptors viz. A1, A2A, A2B and A3. Its physiological importance depends on the affinity of these receptors and the extracellular concentrations reached. ATP acts as a neurotransmitter in both peripheral and central nervous systems. In the peripheral nervous system, ATP is involved in chemical transmission in sensory and autonomic ganglia, whereas in central nervous system, ATP, released from synaptic terminals, induces fast excitatory postsynaptic currents. ATP provides the energetics for all muscle movements, heart beats, nerve signals and chemical reactions inside the body. Adenosine has been traditionally considered an inhibitor of neuronal activity and a regulator of cerebral blood flow. Since adenosine is neuroprotective against excitotoxic and metabolic dysfunctions observed in neurological and ocular diseases, the search for adenosinerelated drugs regulating adenosine transporters and receptors can be important for advancement of therapeutic strategies against these diseases. This review will summarize the therapeutic potential and recent SAR and pharmacology of adenosine and its receptor agonists and antagonists.

Neuromuscular Control of Movement

2018 ◽  
Keyword(s):  
Nervous System ◽  
Sensory Information ◽  
Neuromuscular Control ◽  
Complex Environments ◽  
Locomotor Rhythm ◽  
Motor Responses ◽  
Reflex Pathways ◽  
Local Reflex ◽  
Local Circuits ◽  
And Control

The control of movement is essential for animals traversing complex environments and operating across a range of speeds and gaits. We consider how animals process sensory information and initiate motor responses, primarily focusing on simple motor responses that involve local reflex pathways of feedback and control, rather than the more complex, longer-term responses that require the broader integration of higher centers within the nervous system. We explore how local circuits facilitate decentralized coordination of locomotor rhythm and examine the fundamentals of sensory receptors located in the muscles, tendons, joints, and at the animal’s body surface. These sensors monitor the animal’s physical environment and the action of its muscles. The sensory information is then carried back to the animal’s nervous system by afferent neurons, providing feedback that is integrated at the level of the spinal cord of vertebrates and sensory-motor ganglia of invertebrates.

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