scholarly journals The Nerve Net of the Actinozoa

1935 ◽  
Vol 12 (2) ◽  
pp. 119-138 ◽  
Author(s):  
C. F. A. PANTIN
Keyword(s):  
Mechanical Stimulus ◽  
Electrical Stimulus ◽  
Conducting Layer ◽  
Electrical Excitation ◽  
Sense Organs ◽  
Nerve Net ◽  
Duration Relationship ◽  
The Individual ◽  
Electrical Stimuli ◽  
Stimulation Of

1. Certain features have been supposed to characterise the nerve net. Response is said to vary with the strength of stimulus: and while conduction may occasionally take place in an all or nothing manner, yet in general conduction is supposed to take place with a decrement. To investigate these points, the responses of Calliactis parasitica to mechanical and electrical stimuli have been investigated. 2. Electrical excitation of the column of the anemone shows that a response results from a succession of stimuli and not from a single stimulus. The character of the response is independent of the strength of the individual stimuli. It depends solely upon the number of stimuli and upon the interval of time between them. All responses are highly developed facilitation phenomena. Each electrical stimulus induces a single excitation impulse in the nerve net. 3. But a mechanical stimulus is followed by the discharge of a battery of impulses from the sense organs. These increase in number and frequency with the intensity of the mechanical stimulus. A response may therefore vary with the strength of a mechanical stimulus, but only in relation to the number and frequency of impulses discharged by the sense-organs. 4. Stimulation of the intact column of the anemone shows complete conduction over its whole nerve net. Mechanical stimulation of the disc appears to show conduction with a decrement. Such a stimulus excites a battery of impulses. Each impulse is conducted without decrement, but it facilitates the entrance of succeeding impulses into adjoining sections of the disc nerve net. There is no decrement of excitation strength under any conditions in the nerve net. But there may be a numerical decrement as a battery of impulses spreads from a stimulus. 5. The nerve net is physiologically similar to ordinary nerve. A method is described for determining the strength duration relationship for the threshold of electrical excitation of the nerve net. The relation is of the usual form with a chronaxie of about 2-4σ. The nerve net has well-defined relative and absolute refractory periods: the latter is about 40-65σ. The relation of facilitation to refractory period is considered. 6. The whole nerve net of the column of the anemone acts as a conducting layer in its most simple form, directly transmitting excitation from the stimulus to the muscle. Facilitation takes place between the nerve net and its appropriate muscles. Conduction in the disc nerve net involves facilitation between parts of the nerve net in addition. 7. The true characteristics of the nerve net are diffuse conduction and the extreme development of facilitation. Diffuse conduction may be total, as in the column, or restricted, as in the disc of Calliactis. Facilitation may be between the nerve net and the muscles, or between parts of the nerve net.

The co-ordination of the protective retraction of coral polyps

1957 ◽  
Vol 240 (675) ◽  
pp. 495-529 ◽  
Keyword(s):  
Electrical Stimulation ◽  
Electrical Stimulus ◽  
Simple Theory ◽  
Conducting System ◽  
Common Theme ◽  
Single Shock ◽  
Working Model ◽  
Successive Stimulus ◽  
The Individual ◽  
Stimulation Of

The responses to electrical stimulation of a number of alcyonarian, zoanthid and madreporarian corals are described. All groups studied except gorgonids show extensive coordination over the colony. In Sarcophyton (Alcyonacea) the response is typically local at first but eventually a wave of polyp retraction can be made to spread over the colony. The astraeid corals and the alcyonarian Tubipora have over the whole colony a through-conducting system which has refractory and neuromuscular properties similar to those found in the mesenteries of actinians. In the zoanthid Palythoa successive shocks produce excitation which spreads progressively farther across the colony at each shock for as many as fifty shocks at two-second intervals. The perforate corals , Acropora, Goniopora and Porites respond to a single shock by a co-ordinated retraction of many polyps. Except in Acropora , it is characteristic of the perforate corals studied that stimulation at one point never spreads over the whole colony no matter how many stimuli are applied. The responses of the individual polyps of many corals, including Fungia , are described, and in all there is a similarity to the column, disk and tentacle responses already known in actinians, e.g. Calliactis . The concept of interneural facilitation has been analyzed by use of a working model which shows that the simple theory is inadequate as an explanation of transmission between polyps of certain species because the predicted transmission distances are either too variable or too small compared with the actual distances observed at the first electrical stimulus of the animal. The properties of the co-ordinating systems between the polyps of the various groups of corals have been considered as variations on a common theme, conduction between units which form a network. The various stages from poor co-ordination, through progressive spread at each successive stimulus, to a through-conducting condition have been interpreted as a reflexion of increasing probability of transmission from one all-or-nothing unit of the pathway to the next unit in a population of a large number of units, only a proportion of which may be active at any one time. The units may be interpreted as neurones, as is probable in parts of a single polyp, or as small regions such as polyps within which there is normally through-conduction at the first stimulus.

scholarly journals THE RELATIONS OF THE INDIVIDUAL AMPULLÆ OF THE SEMICIRCULAR CANALS TO THE INDIVIDUAL EYE MUSCLES

1926 ◽  
Vol 8 (5) ◽  
pp. 441-449 ◽  
Author(s):  
S. S. Maxwell ◽  
O. L. Huddleston
Keyword(s):  
Mechanical Stimulation ◽  
Semicircular Canals ◽  
Mechanical Stimulus ◽  
Horizontal Canal ◽  
Eye Muscles ◽  
Reflex Effect ◽  
Strong Contraction ◽  
Rhythmic Contractions ◽  
The Individual ◽  
Stimulation Of

1. The reflex effect of direct mechanical stimulation of the exposed ampulla of the horizontal canal has been graphically recorded for each of the six extrinsic muscles of the eyeball. 2. Stimulation of a horizontal ampulla evokes a strong contraction of the homolateral rectus internus and of the contralateral rectus externus; at the same time the homolateral rectus externus and the contralateral rectus internus relax. 3. A single mechanical stimulus applied to the horizontal ampulla is sometimes followed by a nystagmus resulting from a series of rhythmic contractions of the externus and internus muscles. 4. Excitation of a horizontal ampulla gives rise to weak contractions of the superior and inferior recti and of the two oblique muscles of both eyes, simultaneously with the stronger contractions of the externus and internus respectively. 5. It is pointed out that the small simultaneous contractions of the four muscles just mentioned provide a virtual axis upon which the eyeball rotates. In other words these four act as fixation muscles. 6. It is suggested that some of the abnormal responses to horizontal rotation, seen in clinical cases, are due to the inaction of one or more of the fixation muscles.

Central interaction between the baroreceptor reflexes from the carotid sinus and aortic arch

1979 ◽  
Vol 236 (1) ◽  
pp. H127-H133 ◽  
Author(s):  
J. E. Kendrick ◽  
G. L. Matson ◽  
P. M. Lalley
Keyword(s):  
Aortic Arch ◽  
Carotid Sinus ◽  
Cardiovascular Response ◽  
Carotid Sinus Nerve ◽  
Carotid Baroreceptor ◽  
Baroreceptor Reflexes ◽  
Cardiac Slowing ◽  
The Individual ◽  
Electrical Stimuli ◽  
Stimulation Of

The cardiovascular response to combined stimulation of the aortic nerve (AN) and carotid sinus nerve (CSN) with trains of electrical stimuli was studied in dogs under morphine-chloralose anesthesia. Combined stimulation of both nerves ipsilaterally resulted in systemic arterial depressor responses and cardiac slowing that were 59% and 77% greater (P less than 0.05) than the respective sum of the responses to separate stimulation of these nerves. The depressor response to combined stimulation of these nerves contralaterally was not different (P greater than 0.05) from the sum of the separate responses. However, cardiac slowing to contralateral stimulation of the nerves remained 43% greater (P less than 0.05) than the sum of the individual responses. The results suggest that an interaction between the aortic and carotid baroreceptor reflexes occurs centrally, which causes a greater than additive effect on the autonomic output. The degree of interaction between the reflexes did not change as the delay between the stimulus trains was varied over an interval of 0 and 100 ms. At intervals greater than 100 ms the reflex responses were additive.

Gut perception in humans is modulated by interacting gut stimuli

2002 ◽  
Vol 282 (2) ◽  
pp. G220-G225 ◽  
Author(s):  
Anna M. Accarino ◽  
Fernando Azpiroz ◽  
Juan-R Malagelada
Keyword(s):  
Random Order ◽  
Electrical Stimulus ◽  
Perception Threshold ◽  
Stimulus Response ◽  
Background Stimulation ◽  
Different Types ◽  
Intestinal Distension ◽  
Sensitizing Effect ◽  
Electrical Stimuli ◽  
Stimulation Of

Digestive symptoms depend on multiple interacting gut stimuli, but integration of visceral afferent traffic is poorly understood. Our aim was to elucidate the contribution of simultaneous intestinal stimuli to conscious perception. In 17 healthy subjects, we performed stimulus-response trials of jejunal distensions (1-min duration at 5-min intervals in 8-ml increments) either alone or with a background electrical stimulus, and stimulus-response trials of electrical stimuli (1-min duration at 5-min intervals in 6-mA steps) either alone or with a background intestinal distension. The four stimulus-response trials were performed concomitantly applying the different types of stimuli in random order. Perception was measured on a scale of 0 to 6. Background stimulation markedly increased perception of test stimuli, reducing tolerance from 44 ± 3 to 32 ± 3 ml and from 67 ± 6 to 33 ± 4 mA ( P < 0.05 for both). However, whereas jejunal distensions below the perception threshold did not modify perception of the background stimulus (4 ± 1% change; not significant), unperceived electrical stimuli exerted a sensitizing effect and increased perception of the background distension up to uncomfortable levels (111 ± 40% increment; P < 0.05). In conclusion, activation of different pools of jejunal afferents produces summative effects on perception, and this sensitizing effect can be exerted by unperceived stimulation of mechanoinsensitive jejunal afferents.

Rapid Contractions and Associated Potentials in a Sand-Dwelling Anemone

1969 ◽  
Vol 51 (2) ◽  
pp. 513-528
Author(s):  
PETER E. PICKENS
Keyword(s):  
Maximum Size ◽  
Mechanical Stimulus ◽  
Retractor Muscle ◽  
Mechanical Stimuli ◽  
Nerve Impulses ◽  
Electrical Potentials ◽  
Spread Of Excitation ◽  
Electrical Stimuli ◽  
Withdrawal Response ◽  
Muscle Potential

1. Two kinds of electrical potentials can be recorded from the surface of the. retractor muscle of the anemone, Calamactis, during rapid contraction. These are large muscle action potentials and smaller pulses which are thought to be nerve spikes The latter resemble nerve impulses of higher organisms in that they are all-or-none and of short duration. 2. A nerve spike follows each of a pair of electrical stimuli, but the muscle potential and contraction occur only after the second shock, indicating that facilitation is required at the neuromuscular junction. 3. The size of the muscle potential and of the contraction are correlated with the interval between paired electrical stimuli. Maximum size is reached when stimuli are zoo msec. apart even though the minimum effective interval is 30 msec. 4. A muscle potential precedes contraction only along the upper part of the retractor muscle and this is the part that contracts rapidly during the withdrawal response. The lower retractor does not contract. 5. Conduction velocity along the upper retractor is higher than along the lower. The histological correlate of rapid conduction is a nerve net with large, long, longitudinally oriented fibres. 6. The refractory period of the conducting system of the upper retractor is shorter than that of the lower retractor. Consequently, spread of excitation toward the aboral end is limited if paired stimuli are further apart than 250-300 msec. 7. A mechanical stimulus which is just strong enough to elicit a withdrawal response evokes a single muscle potential of maximum size, suggesting that two nerve impulses closer together than 200 msec. precede the muscle potential. Stronger mechanical stimuli evoke a burst of muscle potentials.

Identification of Mechanoafferent Neurons in Terrestrial Snail: Response Properties and Synaptic Connections

2002 ◽  
Vol 87 (5) ◽  
pp. 2364-2371 ◽  
Author(s):  
Aleksey Y. Malyshev ◽  
Pavel M. Balaban
Keyword(s):  
Avoidance Behavior ◽  
Receptive Fields ◽  
Dorsal Surface ◽  
Mechanical Stimulus ◽  
Terrestrial Snail ◽  
Mechanosensory Neurons ◽  
Intracellular Stimulation ◽  
Pleural Ganglion ◽  
Withdrawal Response ◽  
Stimulation Of

In this study, we describe the putative mechanosensory neurons, which are involved in the control of avoidance behavior of the terrestrial snail Helix lucorum. These neurons, which were termed pleural ventrolateral (PlVL) neurons, mediated part of the withdrawal response of the animal via activation of the withdrawal interneurons. Between 15 and 30 pleural mechanosensory neurons were located on the ventrolateral side of each pleural ganglion. Intracellular injection of neurobiotin revealed that all PlVL neurons sent their axons into the skin nerves. The PlVL neurons had no spontaneous spike activity or fast synaptic potentials. In the reduced “CNS-foot” preparations, mechanical stimulation of the skin covering the dorsal surface of the foot elicited spikes in the PlVL neurons without any noticeable prepotential activity. Mechanical stimulus-induced action potentials in these cells persisted in the presence of high-Mg2+/zero-Ca2+ saline. Each neuron had oval-shaped receptive field 5–20 mm in length located on the dorsal surface of the foot. Partial overlapping of the receptive fields of different neurons was observed. Intracellular stimulation of the PlVL neurons produced excitatory inputs to the parietal and pleural withdrawal interneurons, which are known to control avoidance behavior. The excitatory postsynaptic potentials (EPSPs) in the withdrawal interneurons were induced in 1:1 ratio to the PlVL neuron spikes, and spike-EPSP latency was short and highly stable. These EPSPs also persisted in the high-Mg2+/high-Ca2+ saline, suggesting monosynaptic connections. All these data suggest that PlVL cells were the primary mechanosensory neurons.

Facilitation in Sea Anemones

1952 ◽  
Vol 29 (2) ◽  
pp. 235-254
Author(s):  
D. M. ROSS
Keyword(s):  
Bile Salt ◽  
Standardized Tests ◽  
Single Stimulus ◽  
Living Animal ◽  
Sea Anemones ◽  
Nerve Net ◽  
Reported Effect ◽  
High Doses ◽  
Electrical Stimuli ◽  
Very High

1. The previously reported effect of anemone extracts, the occurrence of quick closing responses to single electrical stimuli in Metridium, has been re-investigated. In standardized tests it was found that whereas hundreds of stimuli are required for each response to a single stimulus in untreated animals, after anemone extract the incidence of such responses is one per nine stimuli. 2. The incidence of these responses falls off with decreasing doses of extract and the effect disappears when less than 1/500th of the material from a single large Metridium is administered. There is no evidence that extracts from ‘stimulated’ and ‘unstimulated’ (i.e. anaesthetized or quick-frozen) anemones differ in potency. Extracts from divided animals show greater activity in the ‘sphincter-disk’ fraction. 3. The incidence of the responses also falls off in time and is highest from 15 to 30 sec. after beginning the treatment. The effect is sporadic and short-lived and responses to two or more successive stimuli are exceptional. 4. A number of treatments, such as drastic changes in pH, KCl(K+ x 8), tetramethylammonium hydroxide (1 : 100), NH4C1 (1 : 340) and especially bile salt and saponin, have similar effects. Drugs with neuro-muscular effects elsewhere (acetylcholine, adrenaline, tyramine, histamine, etc.) were generally ineffective except at very high doses. Food stimulants too were ineffective. 5. From the time relations and other aspects of the responses to single stimuli it is concluded that the effect should not be attributed to a substance with the function of a ‘facilitator’ in the living animal. 6. While the effects are consistent with the passage of occasional adventitious impulses in the nerve net, there is a singular absence of spontaneous or post-stimulus contractions. Certain implications of this feature of the results are discussed.

Memoirs: The Neuro-Muscular Mechanism of the Gill of Pecten

1930 ◽  
Vol s2-73 (291) ◽  
pp. 365-392
Author(s):  
S. B. SETNA
Keyword(s):  
Feeding Habits ◽  
Adductor Muscle ◽  
The Body ◽  
Muscle Fibres ◽  
Direct Stimulation ◽  
Gill Filaments ◽  
Lateral Extent ◽  
Branchial Nerve ◽  
The Individual ◽  
Stimulation Of

Experimental. 1. The contraction of the adductor-muscle which follows stimulation of the palial nerve is preceded by a marked contraction of the ctenidial axis, so that the gill contracts before the adductor-muscle becomes active. This movement of the ctenidium is abolished if the main branchial nerve is cut near its origin. 2. The gills of Pecten possess a neuromuscular mechanism which is to some extent independent of the rest of the body, so that excised gills when stimulated react in the same way as an attached gill. 3. The lamellae of the gill possess two distinct types of movement. (a) When the surface of the gill is stimulated by contact with a glass rod or by carmine particles, the frontal surfaces of the two lamellae approach each other; the movement very often being executed by the lamella which is not actually being stimulated. The lateral extent of these movements (concertina movements) is roughly proportional to the intensity of the stimulus. Such movements normally appear to transfer the bulk of the material on to the mantle. Separation of the main branchial nerve abolishes these movements. (b) Each principal filament is capable of moving the ordinary filaments to which it is attached. This movement (flapping movement) is due to the movements of the interfilamentar junctions which alternatively move up and down at right angles to their length. This motion is independent of the branchial nerve and can be produced by direct stimulation of very tiny pieces of the individual filaments. 4. The significance of gill movements to feeding habits is discussed. The course of food particles depends on the nature of the stimuli affecting the gill. Histological. 5. The ctenidial axis and the principal filaments have a stratum of anastomosing nerve-cells which appear to form a true nerve-net comparable to that of the mantle. 6. The gill receives nerve-fibres from two sources, the brain and the visceral ganglion. The subsidiary branchial nerve is a structure hitherto unknown in the molluscan gill; so far its function is unknown. Each gill has four main longitudinal nerve-trunks. 7. The osphradium of the gill has a much more extensive distribution than has hitherto been supposed. 8. Two sets of muscles exist at the base of the gill-filaments, and these are responsible for movements of the lamellae. The muscle-fibres are non-striated. 9. The principal filaments are connected to the ordinary filaments by processes containing true muscle-cells, and by these cells movements of the filaments are effected.

Control of mouth opening and pharynx protrusion during feeding in the sea anemone Calliactis parasitica

1975 ◽  
Vol 63 (3) ◽  
pp. 615-626
Author(s):  
I. D. McFarlane
Keyword(s):  
Amino Acids ◽  
Electrical Stimulation ◽  
Reduced Glutathione ◽  
Mouth Opening ◽  
Pulse Frequency ◽  
Sea Anemone ◽  
Conducting System ◽  
Nerve Net ◽  
Calliactis Parasitica ◽  
Stimulation Of

1. Activity in all three known conducting systems (the nerve net, SS1, and SS2) may accompany feeding in Calliactis. The most marked response is an increase in pulse frequency in the SS2 (the endodermal slow conducting system) during mouth opening and pharynx protrusion. 2. Electrical stimulation of the SS2 at a frequency of one shock every 5 s elicits mouth opening and pharynx protrusion in the absence of food. 3. A rise in SS2 pulse frequency is also evoked by food extracts, some amino acids, and in particular by the tripeptide reduced glutathione, which produces a response at a concentration of 10(−5) M. 4. Although the SS2 is an endodermal system, the receptors involved in the response to food appear to be ectodermal. 5. The epithelium that lines the pharynx conducts SS1 pulses, but there is some evidence for polarization of conduction.

Memoirs: On the Mantle Cavity and its Contained Organs in the Loricata (Placophora)

1939 ◽  
Vol s2-81 (323) ◽  
pp. 367-390
Author(s):  
C. M. YONGE
Keyword(s):  
Broad Band ◽  
Secondary Structures ◽  
Mantle Cavity ◽  
Sense Organs ◽  
Typical Structure ◽  
Characteristic Structure ◽  
Water Currents ◽  
The Individual

1. The course of the water currents in the mantle cavity of three species of the Chitonida, and one species of the Lepidopleurida, has been determined. 2. Inhalant openings are created anteriorly or laterally by local raising of the girdle. The single exhalant opening is always posterior and confined to the region between the last pair of gills. 3. The exhalant current carries with it the genital and excretory products, and, in the Chitonida, the faeces. 4. The bridging of the pallial grooves in the region of the girdle folds by the post-renal gills (and adanal gills in the Lepidopleurida) completes the functional division of the pallial grooves into inhalant and exhalant chambers. 5. The gills possess the typical structure of ctenidia, and their ciliation is a modification only of that of ctenidia. They are to be regarded as multiplied ctenidia and not as secondary structures. 6. The individual filaments are shortened, attached to those of adjacent gills by long interlocking cilia, and have a broad band of lateral cilia which create the respiratory current. 7. Four possible tracts of mucous glands in the pallial grooves are concerned with the consolidation of sediment. The pallial tracts may be homologous with the hypobranchial glands of the Prosobranchia; all are analogous with these. In the Chitonida sediment is rejected only from the exhalant chamber, in the Lepidopleurida mainly from the inhalant chamber. 8. Osphradia, possibly homologous with those in the Gastropoda, occur in the majority of the Chitonida. With them may be associated anterior sense organs. In the Lepidopleurida they are replaced by branchial and lateral sense organs. All are similar in structure and innervation. They have been considered olfactory in function, but with equal reason may be regarded as tactile organs concerned with the estimation of sediment. 9. The Loricata probably evolved between tide-marks, their characteristic structure being admirably adapted for life on the shore. 10. The reasons for the differences between the structure and habits of the Lepidopleurida and the Chitonida are discussed.

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