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

2020 ◽  
Vol 223 (24) ◽  
pp. jeb233494
Author(s):  
Tigran P. Norekian ◽  
Robert W. Meech
Keyword(s):  
Action Potentials ◽  
Time Course ◽  
Lower Surface ◽  
Muscle Fibres ◽  
Muscle System ◽  
Slow Potentials ◽  
Nerve Tracts ◽  
System Part ◽  
And Function ◽  
Stimulation Of

ABSTRACTAlthough the bell-shaped nectophores of the siphonophore Nanomia bijuga are clearly specialized for locomotion, their complex neuroanatomy described here testifies to multiple subsidiary functions. These include secretion, by the extensively innervated ‘flask cells' located around the bell margin, and protection, by the numerous nematocytes that line the nectophore's exposed ridges. The main nerve complex consists of a nerve ring at the base of the bell, an adjacent column-shaped matrix plus two associated nerve projections. At the top of the nectophore the upper nerve tract appears to have a sensory role; on the lower surface a second nerve tract provides a motor input connecting the nectophore with the rest of the colony via a cluster of nerve cells at the stem. N. bijuga is capable of both forward and backward jet-propelled swimming. During backwards swimming the water jet is redirected by the contraction of the Claus' muscle system, part of the muscular velum that fringes the bell aperture. Contractions can be elicited by electrical stimulation of the nectophore surface, even when both upper and lower nerve tracts have been destroyed. Epithelial impulses elicited there, generate slow potentials and action potentials in the velum musculature. Slow potentials arise at different sites around the bell margin and give rise to action potentials in contracting Claus’ muscle fibres. A synaptic rather than an electrotonic model more readily accounts for the time course of the slow potentials. During backward swimming, isometrically contracting muscle fibres in the endoderm provide the Claus' fibres with an immobile base.

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.

Structure and Function of the Lateral Giant Neurone of the Primitive Crustacean Anaspides Tasmaniae

1979 ◽  
Vol 78 (1) ◽  
pp. 121-136
Author(s):  
GERALD E. SILVEY ◽  
IAN S. WILSON
Keyword(s):  
Action Potentials ◽  
Tactile Stimulation ◽  
Large Diameter ◽  
Whole Body ◽  
Giant Fibre ◽  
Single Action ◽  
Giant Neurone ◽  
And Function ◽  
Thoracic And Abdominal ◽  
Stimulation Of

The syncarid crustacean Anaspides tasmaniae rapidly flexes its free thoracic and abdominal segments in response to tactile stimulation of its body. This response decrements but recovers in slightly more than one hour. The fast flexion is evoked by single action potentials in the lateral of two large diameter fibres (40 μm) which lie on either side of the cord. The lateral giant fibre is made up of fused axons of 11 neurones, one in each of the last 5 thoracic and 6 abdominal ganglia. The soma of each neurone lies contralateral to the axon. Its neurite crosses that of its counterpart in the commissure and gives out dendrites into the neuropile of each hemiganglion. The lateral giant neurone receives input from the whole body but fires in response only to input from the fourth thoracic segment posteriorly. Both fibres respond with tactile stimulation of only one side. Since neither current nor action potentials spread from one fibre to the other, afferents must synapse with both giant neurones. The close morphological and physiological similarities of the lateral giant neurone in Anaspides to that in the crayfish (Eucarida) suggest that the lateral giant system arose in the ancestor common to syncarids and eucarids, prior to the Carboniferous.

Neuromuscular Physiology of the Longitudinal Muscle of the Earthworm, Lumbricus Terrestris

1974 ◽  
Vol 60 (2) ◽  
pp. 453-467
Author(s):  
C. D. DREWES ◽  
R. A. PAX
Keyword(s):  
Time Course ◽  
Longitudinal Muscle ◽  
Lumbricus Terrestris ◽  
Single Pulse ◽  
Repetitive Stimulation ◽  
Muscle Fibres ◽  
Mechanical Responses ◽  
Segmental Nerve ◽  
Earthworm Lumbricus ◽  
Stimulation Of

1. Patterns of innervation of the longitudinal muscle of the earthworm, Lumbricus terrestris, were examined electrophysiologically. 2. The longitudinal musculature of a segment is innervated by relatively few axons, a fast and slow axon being present in segmental nerve I and in the double nerve, segmental nerve II-III. 3. Single-pulse stimulation of the fast axon produces large external muscle potentials and small twitch-like contractions, which with repetitive stimulation are antifacilitating. 4. Repetitive stimulation of the slow axon produces large, slowly developing and sustained mechanical responses, with electrical and mechanical responses showing summation and facilitation. 5. The amplitude and time course of slow mechanical responses are related to the frequency of stimulation. 6. Individual longitudinal muscle fibres are innervated by either the fast or slow axon in a segmental nerve, or by both fast and slow axons. 7. No evidence was found for peripheral inhibitory innervation of the longitudinal muscle.

Gastric vagal-evoked and greater splanchnic-evoked unitary responses in the hypothalamus

1993 ◽  
Vol 264 (6) ◽  
pp. G1133-G1141 ◽  
Author(s):  
W. D. Barber ◽  
C. S. Yuan
Keyword(s):  
Action Potentials ◽  
Time Course ◽  
Splanchnic Nerve ◽  
Nerve Fibers ◽  
Hypothalamic Neurons ◽  
Proximal Stomach ◽  
Neuronal Interactions ◽  
Greater Splanchnic Nerve ◽  
Two Peaks ◽  
Stimulation Of

Gastric vagal and greater splanchnic nerve fibers were electrically stimulated to localize and characterize neuronal interactions in the hypothalamus of anesthetized cats. Extracellular recordings from 635 hypothalamic units were identified that responded to electrical stimulation of the left greater splanchnic nerve or gastric vagal fibers serving the proximal stomach. A total of 504 hypothalamic units in this group received input from both gastric vagal and greater splanchnic nerves. The gastric vagal-evoked hypothalamic (GVeH) and greater splanchnic-evoked hypothalamic (SeH) responses were widely distributed in the medial, paraventricular, and dorsomedial nuclei and lateral hypothalamus. The conduction velocity of the SeH response was significantly greater than the GVeH response. The latency of the SeH response showed two peaks [58 +/- 15.7 (SD) ms and 136 +/- 18.3 (SD) ms] indicating that the splanchnic input terminated on two different groups or populations of hypothalamic neurons. It also suggested that different pathways or fiber diameters in the pathway may be involved in the transmission of splanchnic input to the hypothalamus. The majority of the GVeH and SeH unitary responses were multiple spikes or short trains of action potentials. Excitatory and inhibitory responses were observed in tonically active hypothalamic units that responded to gastric vagal or greater splanchnic input. The duration of decreased excitability to gastric vagal or greater splanchnic input was significantly greater than the period of increased excitability. The condition-test paradigm was used to determine the time course of convergent gastric vagal-greater splanchnic input on single hypothalamic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium-dependent receptor current in a new mechanoreceptor preparation

1994 ◽  
Vol 72 (6) ◽  
pp. 3026-3028 ◽  
Author(s):  
M. Juusola ◽  
E. A. Seyfarth ◽  
A. S. French
Keyword(s):  
Mechanical Stimulation ◽  
Action Potentials ◽  
Time Course ◽  
Receptor Potential ◽  
Sodium Ions ◽  
Similar Time ◽  
Sodium Dependent ◽  
Restricted Environment ◽  
Intracellular Microelectrodes ◽  
Stimulation Of

1. Intracellular microelectrodes recorded the receptor potential and receptor current in the neurons of spider slit sense organs during mechanical stimulation of the slits. 2. Mechanical stimulation produced two patterns of action potential discharge, corresponding to the two groups of neurons described previously by electrical stimulation. 3. Tetrodotoxin eliminated the action potentials and revealed a receptor potential with both static and adapting components. Voltage clamp gave an inward receptor current with a similar time course. 4. Replacement of sodium ions in the bath reversibly eliminated the receptor current, indicating that it is carried by sodium ions. However, this effect was comparatively slow, suggesting that the tips of the sensory dendrites lie in a chemically restricted environment.

scholarly journals Excitation of the nerve-muscle system in Crustacea

1946 ◽  
Vol 133 (872) ◽  
pp. 374-389 ◽  
Keyword(s):  
Time Course ◽  
Mechanical Response ◽  
Motor Nerve ◽  
Low Frequency ◽  
Minor Role ◽  
Muscle Fibres ◽  
Activation Process ◽  
Muscle System ◽  
Nerve Impulses ◽  
Crustacean Muscle

The nature of the action potential and the mechanical response of crustacean muscle is investigated. If electric shocks of sufficient intensity are applied to the muscle, graded local contractions occur at the cathode. If the intensity of the stimuli is further increased, propagated action potentials, up to 40 mV, are recorded, accompanied by vigorous twitches of the active fibres. The conduction velocity of the muscle impulse is about 20 cm./sec., at 20° C, and its wavelength about 2—3 mm. The mechanical and electrical responses of the muscle to motor nerve stimulation are local or propagated, depending upon the number and frequency of the nerve impulses. With single, or low-frequency, motor nerve impulses a negative potential change is recorded in the vicinity of the nerve endings. It spreads decrementally 2-3 mm. along the muscle fibres, and at 17° C rises to a peak in 3 msec, and falls to one half in about 6 msec. Because of its analogy to the junctional potential of curarized vertebrate muscle it will be referred to as 'end-plate potential’ (e. p. p.). The spatial characteristics of the e. p. p. provide evidence for a discrete ‘focal’ innervation of crustacean muscle fibres, similar to that in vertebrates. In many muscles, with repetitive stimulation, successive e. p. p.’s continue to grow in amplitude for 0⋅3-0⋅5 sec. The degree and time course of this ‘facilitation’ varies greatly in different muscles; depending upon initial size and rate of growth of successive e. p. p.’s, ‘fast’ and ‘slow ’ systems can be distinguished. At high frequencies (above 100 per sec.), e. p. p.’s sum to a plateau of several times their individual height. When the e. p. p.’s have grown or summed to a ‘threshold’ level, propagated spikes are set up. Spikes in individual fibres are usually asynchronous and occur at a lower rate than e. p. p.’s. If the e. p. p. is slightly below ‘threshold’, abortive spikes are observed. A prolonged series of e. p. p.’s is associated with a relatively slow maintained contraction of the junctional region. Propagated spikes, on the other hand, are accompanied by quick twitches of the active muscle fibres. This difference is seen clearly by direct inspection of the exposed muscle fibres, but not by recording the overall tension of the muscle. In many muscles, local junctional responses account for more than 50% of the maximum observed tension. Electric recording on the intact animal shows that a good deal of the normal limb muscle activity is based on e. p. p.’s and local contractions. Propagated muscle spikes were seen only during fast and powerful reactions. The rate of contraction varies with the frequency of motor impulses as a higher than second power function. This relation, and especially the origin of the very slow contraction at low frequency, is discussed. Recruitment of individual muscle fibres plays only a minor role; the main factor is the rate of summation of the local mechanical activation process at the junction. A further factor influencing the speed of contraction is the spatial spread of the active region, which controls the extent of internal elastic shortening of the muscle. The various links of the neuro-muscular transmission chain are discussed and compared with the analogous processes in vertebrates.

Adrenergic Stimulation of Regional Plasminogen Activator Release in Rabbits

1992 ◽  
Vol 68 (05) ◽  
pp. 545-549 ◽  
Author(s):  
W L Chandler ◽  
S C Loo ◽  
D Mornin
Keyword(s):  
Lower Extremity ◽  
Plasminogen Activator ◽  
Beta Blocker ◽  
Time Course ◽  
Vascular System ◽  
Adrenergic Stimulation ◽  
Epinephrine Administration ◽  
Adrenergic Antagonist ◽  
Vascular Beds ◽  
Stimulation Of

SummaryThe purpose of this study was to determine whether different regions of the rabbit vascular system show variations in the rate of plasminogen activator (PA) secretion. To start, we evaluated the time course, dose response and adrenergic specificity of PA release. Infusion of 1 µg/kg of epinephrine stimulated a 116 ± 60% (SD) increase in PA activity that peaked 30 to 60 s after epinephrine administration. Infusion of 1 µg/kg of norepinephrine, isoproterenol and phenylephrine had no effect on PA activity. Pretreatment with phentolamine, an alpha adrenergic antagonist, blocked the release of PA by epinephrine while pretreatment with the beta blocker propranolol had no effect. This suggests that PA release in the rabbit was mediated by some form of alpha receptor.Significant arterio-venous differences in basal PA activity were found across the pulmonary and splanchnic vascular beds but not the lower extremity/pelvic bed. After stimulation with epinephrine, PA activity increased 46% across the splanchnic bed while no change was seen across the lower extremity/pelvic bed. We conclude that several vascular beds contribute to circulating PA activity in the rabbit, and that these beds secrete PA at different rates under both basal and stimulated conditions.

Epidermal Laser Stimulation of Action Potentials in the Frog Sciatic Nerve

2008 ◽  
Author(s):  
Nichole M. Jindra ◽  
Robert J. Thomas ◽  
Douglas N. Goddard ◽  
Michelle L. Imholte
Keyword(s):  
Sciatic Nerve ◽  
Action Potentials ◽  
Laser Stimulation ◽  
Frog Sciatic Nerve ◽  
Stimulation Of

scholarly journals Potentiometric measurement of membrane action potentials in frog muscle fibres

1966 ◽  
Vol 183 (1) ◽  
pp. 152-166 ◽  
Author(s):  
B. Frankenhaeuser ◽  
B. D. Lindley ◽  
R. S. Smith
Keyword(s):  
Action Potentials ◽  
Frog Muscle ◽  
Muscle Fibres ◽  
Membrane Action ◽  
Potentiometric Measurement

Tetrodotoxin-resistant release of ATP from superfused rabbit detrusor muscle during electrical field stimulation in the presence of luciferin–luciferase

1984 ◽  
Vol 62 (1) ◽  
pp. 153-156 ◽  
Author(s):  
Archana Chaudhry ◽  
John W. Downie ◽  
Thomas D. White
Keyword(s):  
Action Potentials ◽  
Electrical Field Stimulation ◽  
Detrusor Muscle ◽  
Electrical Field ◽  
Stimulation Parameters ◽  
Rabbit Bladder ◽  
Firefly Luciferin ◽  
Rabbit Urinary Bladder ◽  
Stimulation Of

The present study was carried out to assess the possible role of ATP in the noncholinergic, nonadrenergic transmission in the rabbit urinary bladder. When rabbit detrusor muscle strips were superfused with medium containing firefly luciferin–luciferase and stimulated transmurally at low stimulation parameters, tetrodotoxin-sensitive contractions were obtained but no release of ATP could be detected. However, at somewhat higher stimulation parameters, release of ATP was observed. This release of ATP was not diminished by tetrodotoxin indicating that ATP was not likely released as a result of propagated action potentials in nerves. Because contractions persisted in the presence of tetrodotoxin, it is possible that the ATP might have been released as a result of direct electrical stimulation of the muscle. These results do not support the idea that ATP is released as a neurotransmitter in the rabbit bladder.

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