scholarly journals Studies on the Myoneural Physiology of Echinodermata

1955 ◽  
Vol 32 (1) ◽  
pp. 59-69
Author(s):  
WALTER POPLE ◽  
D. W. EWER
Keyword(s):  
Radial Nerve ◽  
Nerve Ring ◽  
Delayed Response ◽  
High Frequencies ◽  
Nerve Tracts ◽  
Synaptic Junctions ◽  
Post Tetanic Potentiation ◽  
Frequency Of Stimulation ◽  
Nervous Conduction ◽  
Delayed Responses

1. The general characteristics of circumoral nervous conduction in Cucumaria have been studied by the use of preparations consisting of the retractor muscles and radial nerves of two adjoining radii joined by a sector of circumoral nerve ring and by the use of similar preparations of all five retractor muscles and the complete circumoral nerve ring. 2. The characteristics of the responses of muscles stimulated by way of circumoral nerve tracts are as follows: the muscles respond with a quick and a delayed response; the magnitude of these responses depends upon the intensity of stimulation applied to an adjoining radial nerve, but is unaffected by frequency of stimulation up to a rate of 10 s./sec.; at high frequencies of stimulation both quick and delayed responses are depressed; the conduction velocity of impulses releasing quick and delayed responses is of the same order; the delayed response may show a prolonged facilitation previously analogized with post-tetanic potentiation. In these characteristics the muscular responses to impulses conducted in the circumoral nerve tracts are similar to those found to impulses conducted in the radial nerve tracts alone. 3. When, in a preparation of the five-retractor muscles, a radial nerve is stimulated, the muscles of radii nearer the stimulated nerve contract more strongly than those of radii further away. 4. Evidence is presented in favour of the view that this ‘decremental’ effect is dependent upon the geometrical arrangement of the fibre tracts in the circumoral nerve. The effect is not dependent upon frequency-sensitive synaptic junctions nor upon proprioceptive relays.

scholarly journals Studies on the Myoneural Physiology of Echinodermata

1954 ◽  
Vol 31 (1) ◽  
pp. 114-126
Author(s):  
WALTER POPLE ◽  
D. W. EWER
Keyword(s):  
Radial Nerve ◽  
Delayed Response ◽  
Quick Response ◽  
Direct Stimulation ◽  
Pharyngeal Muscle ◽  
Motor Complex ◽  
Double Response ◽  
Single Response ◽  
Frequency Of Stimulation ◽  
Stimulation Of

1. A myoneural preparation of Cucumaria sykion (Lampert) comprising a pharyngeal muscle and the corresponding radial nerve is described. A brief account is given of the histology of the preparation. 2. Direct stimulation of the muscle gives a single response. Above fusion frequency the tension developed by the muscle increases with increasing intensity of stimulation, but it is unaffected by the frequency of stimulation. 3. Stimulation of the radial nerve elicits a double response from the muscle. There is a ‘quick’ response which shows no myoneural facilitation and a ‘delayed’ response which shows a well-marked and prolonged facilitation. 4. The tensions developed by both quick and delayed responses depend upon the intensity of stimulation applied to the radial nerve. Both responses show well- marked refractoriness at stimulation frequencies above about 10 stim./sec. 5. It is suggested that the delayed response arises from the activity of the internmcial neurones in the motor complex, and that this is also the locus of the prolonged facilitation shown by the delayed response. 6. The similarity of the properties of this system with certain features of the chordate nervous system are pointed out, but it is considered that any simple phylogenetic conclusions are unwarranted.

The enteric nervous system of echinoderms: unexpected complexity revealed by neurochemical analysis

2001 ◽  
Vol 204 (5) ◽  
pp. 865-873
Author(s):  
J.E. Garcia-Arraras ◽  
M. Rojas-Soto ◽  
L.B. Jimenez ◽  
L. Diaz-Miranda
Keyword(s):  
Nervous System ◽  
Enteric Nervous System ◽  
Digestive Tract ◽  
Radial Nerve ◽  
Digestive System ◽  
Nerve Ring ◽  
Point Of View ◽  
Distinct Component ◽  
Future Studies ◽  
Neurochemical Analysis

Echinoderms are one of the most important groups of metazoans from the point of view of evolution, ecology and abundance. Nevertheless, their nervous system has been little studied. Particularly unexplored have been the components of the nervous system that lie outside the ectoneural and hyponeural divisions of the main nerve ring and radial nerve cords. We have gathered information on the nervous components of the digestive tract of echinoderms and demonstrate an unexpected level of complexity in terms of neurons, nerve plexi, their location and neurochemistry. The nervous elements within the digestive system consist of a distinct component of the echinoderm nervous system, termed the enteric nervous system. However, the association between the enteric nervous system and the ectoneural and hyponeural components of the nervous system is not well established. Our findings also emphasize the importance of the large lacunae in the neurobiology of echinoderms, a feature that should be addressed in future studies.

Evidence That Post-Tetanic Potentiation Is Mediated by Neuropeptide Release in Aplysia

2001 ◽  
Vol 86 (6) ◽  
pp. 2845-2855 ◽  
Author(s):  
Lyle E. Fox ◽  
Philip E. Lloyd
Keyword(s):  
Motor Neurons ◽  
High Frequency ◽  
Tetanic Stimulation ◽  
Neuropeptide Release ◽  
Neuromuscular Synapses ◽  
Excitatory Junction Potentials ◽  
Post Tetanic Potentiation ◽  
Central Synapses ◽  
Activity Dependent ◽  
Frequency Of Stimulation

Many neuromuscular and central synapses exhibit activity-dependent plasticity. The sustained high-frequency firing needed to elicit some forms of plasticity are similar to those often required to release neuropeptides. We wanted to determine if neuropeptide release could contribute to post-tetanic potentiation (PTP) and chose neuromuscular synapses in buccal muscle I3a to explore this issue. This muscle is innervated by two motor neurons (termed B3 and B38) that show PTP in response to tetanic stimulation. B3 and B38 use glutamate as their fast transmitter but express different modulatory neuropeptides. B3 expresses FMRFamide, a neuropeptide that only slightly increases its own excitatory junction potentials (EJPs). B38 expresses the small cardioactive peptide (SCP), a neuropeptide that dramatically increases its own EJPs. It was our hypothesis that SCP released from B38's terminals during tetanic stimulation mediated a component of PTP for B38. Because no antagonist to SCP currently exists, we used several indirect approaches to test this hypothesis. First, we studied the effects of increasing stimulation frequency during the tetanus or lowering temperature on PTP. Both of these changes are known to dramatically increase SCP release. We found that increasing the frequency of stimulation increased PTP for both neurons; however, the effects were larger for B38. Decreasing the temperature tended to reduce PTP for B3, while increasing PTP for B38. These results were consistent with known properties of SCP release from B38. Next we selectively superfused the neuromuscular synapses with exogenous SCP to determine if this would occlude the effects of SCP released from B38 during a tetanus. We found that exogenous SCP dramatically reduced PTP for B38 but had little effect on PTP for B3. Thus our results support the hypothesis that physiological stimulation of B38 elicits PTP that is predominantly dependent on the release of SCP from its own terminals. They also demonstrate that the mechanisms underlying PTP can be very different for two motor neurons innervating the same target muscle.

The Involvement of Nerves in the Epithelial Control of Crumpling Behaviour in a Hydrozoan Jellyfish

1981 ◽  
Vol 94 (1) ◽  
pp. 203-218 ◽  
Author(s):  
MICHAEL G. KING ◽  
ANDREW N. SPENCER
Keyword(s):  
Radial Nerve ◽  
Recording Electrode ◽  
Polyorchis Penicillatus ◽  
Nerve Bundles ◽  
Synaptic Junctions ◽  
Stimulating Electrodes ◽  
Nerve Muscle ◽  
Radial Muscle ◽  
Muscle Potential

1. The excitation pathways mediating the protective crumpling behaviour of Polyorchis penicillatus were studied with electrophysiological and ultrastructural techniques. 2. Stimulating the subumbrellar endoderm consistently resulted in a complex crumpling potential when recorded with suction electrodes from radial muscle (the prime effector). The potential represents the summation of a quick radial muscle potential (RMP) and a slow endodermal canal pulse (ECP). 3. The latencies of ECPs recorded from radial muscle during crumpling were directly proportional to the distance between the recording electrode and the subumbrellar stimulating electrode. Conversely, the latencies of RMPs, which were not tightly time-coupled to ECPs, were more directly related to the distance of the recording and stimulating electrodes from the marginal or apical termini of the radial muscle. 4. Stimulating the exumbrellar ectoderm resulted in a variable crumpling response, typically occurring after facilitation of numerous exumbrellar pulses (EPs). Since exumbrellar stimulation did not usually excite endoderm, the response recorded from radial muscle normally involved a simple RMP, un-associated with an ECP. 5. Typical synaptic junctions were observed between radial muscle processes and marginal neurites and between radial muscle and neurites of the radial nerve bundles along the length of the muscle. 6. The independence of the ECP and RMP conducting pathways demonstrates that endoderm does not provide the direct source of radial muscle excitation and the initiation of RMPs at points of known (marginal) and suspected (apical) nerve-muscle contact suggests the involvement of nerves in the control of crumpling behaviour. 7. These results are discussed in the light of other examples of active neuronal-epithelial interaction.

Delayed firing rate responses to temperature in diencephalic slices

1992 ◽  
Vol 263 (3) ◽  
pp. R679-R684
Author(s):  
J. B. Dean ◽  
J. A. Boulant
Keyword(s):  
Firing Rate ◽  
Intrinsic Property ◽  
Thermal Stimulation ◽  
Delayed Response ◽  
Neuronal Responses ◽  
Tissue Slices ◽  
Hypothalamic Temperature ◽  
Firing Rates ◽  
Thermoregulatory Responses ◽  
Delayed Responses

Thermoregulatory responses may be delayed in onset and offset by several minutes after changes in hypothalamic temperature. Our preceding study found neurons that displayed delayed firing rate responses during clamped thermal stimulation in remote regions of rat diencephalic tissue slices. The present study looked for similar delayed firing rate responses during clamped (1.5-10 min) changes in each neuron's local temperature. Of 26 neurons tested with clamped thermal stimulation, six (i.e., 23%) showed delayed responses, with on-latencies of 1.0-7.8 min. These neurons rarely showed off-latencies, and the delayed response was not eliminated by synaptic blockade. The on-latencies and ranges of local thermosensitivity were similar to delayed neuronal responses to remote temperature; however, remote-sensitive neurons displayed off-latencies, higher firing rates at 37 degrees C, and greater sensitivity to thermal stimulation. Our findings suggest that delayed thermosensitivity is an intrinsic property of certain neurons and may initiate more elaborate or prolonged delayed responses in synaptically connected diencephalic networks. These networks could explain the delayed thermoregulatory responses observed during hypothalamic thermal stimulation.

Echinoderm Nervous System

2018 ◽  
Author(s):  
Carlos A. Díaz-Balzac ◽  
José E. García-Arrarás
Keyword(s):  
Nervous System ◽  
Radial Nerve ◽  
Regulatory Networks ◽  
Nerve Ring ◽  
Neural Net ◽  
System P ◽  
Embryonic Nervous System ◽  
Body Wall Muscles ◽  
Areas Of Interest ◽  
Nerve Cords

The nervous system of echinoderms has been studied for well over a century. Nonetheless, the information available is disparate, with in-depth descriptions for the nervous component of some groups or of particular organs while scant data is available for others. The best studied representatives to date are the nervous system of echinoid embryos and larva, and the adult holothurian nervous system. Although described sometimes inaccurately as a neural net, the echinoderm nervous system consists of well-defined neural structures. This is observed since early embryogenesis when activation of the anterior neuroectoderm gene regulatory networks initiate the formation of the embryonic nervous system. This system then undergoes expansion and differentiation to form the larval nervous system, which is centered on the ciliary bands. This “simpler” nervous system is then metamorphosed into the adult echinoderm nervous system. The adult echinoderm nervous system is composed of a central nervous system made up of a nerve ring connected to a series of radial nerve cords. Peripheral nerves extending from the radial nerve cords or nerve ring connect with the peripheral nervous system, located in other organs or effectors including the viscera, podia, body wall muscles, and connective tissue. Both the central and peripheral nervous systems are composed of complex and diverse subdivisions. These are mainly characterized by the expression of neurotransmitters, namely acetylcholine, catecholamines, histamine, amino acids, GABA, and neuropeptides. Other areas of interest include the amazing regenerative capabilities of echinoderms that have been shown to be able to regenerate their nervous system components; and the analysis of the echinoderm genome that has provided essential insights into the molecular basis of how echinoderms develop an adult pentaradial symmetry from bilaterally symmetric larvae and the role of the nervous system in this process.

scholarly journals Structure and function of the nervous system in nectophores of the siphonophore Nanomia bijuga

2020 ◽  
Author(s):  
Tigran P. Norekian ◽  
Robert W. Meech
Keyword(s):  
Electrical Stimulation ◽  
Nerve Ring ◽  
Synaptic Delay ◽  
Surface Epithelium ◽  
Muscle Fibres ◽  
List Type ◽  
Muscle System ◽  
Neural Input ◽  
Nerve Tracts ◽  
And Function

SummaryAlthough Nanomia nectophores are specialized for locomotion, their cellular elements and complex nerve structures suggest they have multiple subsidiary functions.The main nerve complex is a nerve ring, an adjacent columnar-shaped matrix plus two associated nerve projections. An upper nerve tract appears to provide a sensory input while a lower nerve tract connects with the rest of the colony.The nerve cell cluster that gives rise to the lower nerve tract may relay information from the colony stem.The structure of the extensively innervated “flask cells” located around the bell margin suggests a secretory function. They are ideally placed to release chemical messengers or toxins into the jet of water that leaves the nectophore during each swim.The numerous nematocytes present on exposed nectophore ridges appear to have an entangling rather than a penetrating role.Movements of the velum, produced by contraction of the Claus’ muscle system during backwards swimming, can be elicited by electrical stimulation of the surface epithelium even when the major nerve tracts serving the nerve ring have been destroyed (confirming Mackie, 1964).Epithelial impulses generated by electrical stimulation elicit synaptic potentials in Claus’ muscle fibres. Their amplitude suggests a neural input in the vicinity of the Claus’ muscle system. The synaptic delay is <1.3 ms (Temperature 11.5 to 15° C).During backward swimming radial muscle fibres in the endoderm contract isometrically providing the Claus’ fibres with a firm foundation.Summary StatementNanomia colonies have specialized swimming bells capable of backwards swimming; thrust is redirected by an epithelial signal that leads to muscle contraction via a synaptic rather than an electrotonic event.

scholarly journals Phosphorylation in vivo of the P light chain of myosin in rabbit fast and slow skeletal muscles

1984 ◽  
Vol 218 (3) ◽  
pp. 841-847 ◽  
Author(s):  
S A Westwood ◽  
O Hudlicka ◽  
S V Perry
Keyword(s):  
Light Chain ◽  
Skeletal Muscles ◽  
Time Course ◽  
Electrophoretic Mobilities ◽  
Slow Twitch Muscle ◽  
Post Tetanic Potentiation ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Frequency Of Stimulation

The P light chain of myosin is partially phosphorylated in resting slow and fast twitch skeletal muscles of the rabbit in vivo. The extent of P light-chain phosphorylation increases in both muscles on stimulation. Rabbit slow-twitch muscles contain two forms of the P light chain that migrate with the same electrophoretic mobilities as the two forms of P light chain in rabbit ventricular muscle. The rate of phosphorylation of the P light chain in slow-twitch muscle is slower than its rate of phosphorylation in fast-twitch muscles during tetanus. The rate of P light-chain dephosphorylation is slow after tetanic contraction of fast-twitch muscles in vivo. The time course of dephosphorylation does not correlate with the decline of post-tetanic potentiation of peak twitch tension in rabbit fast-twitch muscles. The frequency of stimulation is an important factor in determining the extent of P light-chain phosphorylation in fast- and slow-twitch muscles.

scholarly journals Enzymic and metabolic adaptations in the gastrocnemius, plantaris and soleus muscles of hypocaloric rats

1989 ◽  
Vol 261 (1) ◽  
pp. 219-225 ◽  
Author(s):  
M S M Ardawi ◽  
M F Majzoub ◽  
I M Masoud ◽  
E A Newsholme
Keyword(s):  
Citrate Synthase ◽  
Muscle Relaxation ◽  
Lactate Production ◽  
Relaxation Rates ◽  
High Frequencies ◽  
Metabolic Adaptations ◽  
Hydroxyacyl Coa Dehydrogenase ◽  
Oxoglutarate Dehydrogenase ◽  
Frequency Of Stimulation ◽  
Normal Food

1. The effect of hypocaloric feeding (25% of normal food intake for 21 days) of rats on the enzymic and metabolic adaptations in the gastrocnemius, plantaris and soleus muscles was studied. 2. In control and hypocaloric rats the muscle relaxation rates at 100 Hz were 35.76 and 11.38% force loss/10 ms respectively. Control rats exhibited enhanced force of muscle contraction as the frequency of stimulation increased from 10 to 100 Hz, with maximum force being at 100 Hz. Hypocaloric rats exhibited a decrease in the increment of force being exerted at high frequencies, with maintenance of force at lower stimulatory frequencies. 3. In muscles of hypocaloric rats, there were significant decreases in the maximal activities of hexokinase (17.6-37.0%), 6-phosphofructokinase (22.7-34.2%), pyruvate kinase (21.2-36.0%), citrate synthase (34.1-41.5%), oxoglutarate dehydrogenase (29.4-52.4%) and 3-hydroxyacyl-CoA dehydrogenase (26.7-32.1%), whereas the activities of glycogen phosphorylase increased (23.8-43.4%) compared with control values. 4. In soleus-muscle strip preparations of hypocaloric rats, there were significant decreases in the rates of lactate production (28.1%) and glucose oxidation (32.6%) compared with control preparations. 5. Mitochondrial preparations from muscles of hypocaloric rats incubated with various substrates exhibited decreased rates of oxygen uptake compared with control preparations. 6. In muscles of hypocaloric rats (gastrocnemius and soleus), there were significant decreases in the concentrations of glycogen (P less than 0.001) and phosphocreatine (P less than 0.001) and increases in those of pyruvate (P less than 0.001), lactate (P less than 0.001) and ADP (P less than 0.001), whereas those of ATP and AMP remained unchanged. 7. Calculated [lactate]/[pyruvate] and [ATP]/[ADP] ratios exhibited significant increases (P less than 0.05) and decreases (P less than 0.05) in muscles of hypocaloric rats respectively. 8. The results are discussed in relation to the genesis of muscle dysfunction caused by malnutrition.

Ultrastructure of the circumoral nerve ring and the radial nerve cords in holothurians (Echinodermata)

Zoomorphology ◽  
2006 ◽  
Vol 125 (1) ◽  
pp. 27-38 ◽  
Author(s):  
Vladimir S. Mashanov ◽  
Olga R. Zueva ◽  
Thomas Heinzeller ◽  
Igor Yu. Dolmatov
Keyword(s):  
Radial Nerve ◽  
Nerve Ring ◽  
Nerve Cords
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