scholarly journals The Nerve Net of the Actinozoa

1935 ◽  
Vol 12 (2) ◽  
pp. 139-155
Author(s):  
C. F. A. PANTIN
Keyword(s):  
Intact Animal ◽  
Sense Organ ◽  
Conduction System ◽  
Sphincter Muscle ◽  
Nerve Net ◽  
Conducting Path ◽  
Column Wall ◽  
Simple Part ◽  
Single Set ◽  
Stimulation Of

1. Stimulation of the column of the anemone Calliatis parasitica elicits a graded series of responses. Each response is primarily due to the action of a single set of muscles. The means by which this effect is produced is physiologically simple. Part of the nerve net beneath the intact column behaves as a single conducting unit and the various muscles communicate with it. The muscles, however, are only activated through the facilitation of a series of impulses. Each muscle has its own appropriate frequency range, to which a facilitated response can be obtained. The range of frequencies is extraordinarily low, from 1 impulse in 1 sec. to 1 impulse in 10 sec. 2. "Interneural" facilitation can be demonstrated between adjacent conducting units of the nerve net of the disc. From various points on the disc several stimuli may be required to establish a conducting path to the sphincter muscle. The apparent continuity of conduction throughout the column in the intact animal is due to specialised tracts running vertically up the mesenteries. These are joined by a conducting ring in the neighbourhood of the sphincter. In addition to this "through-conduction" system, there is a general nerve net within the column wall in which interneural facilitation is evident. 3. The velocity of conduction in the general nerve net of the column has the slow rate of 10-20 cm. per sec. But for the sphincter-mesenteric system the rate is over 1 metre per sec. 4. The relative development of both interneural facilitation and of conduction velocity within the nerve net give consistent pictures of its physiological organisation. These agree with its morphological organisation. 5. Comparison with other species shows that the through-conduction system is a specialisation, developed in varying degrees in different species. It is most highly developed where protective reactions are most perfect, as in Calliactis. 6. The importance of the "impulse group" propagated from a stimulated sense organ as the natural unit in behaviour of Calliactis is discussed.

scholarly journals Nerve Nets and Conducting Systems in Sea Anemones: Two Pathways Excite Tentacle Contractions in Calliactis Parasitica

1984 ◽  
Vol 108 (1) ◽  
pp. 137-149
Author(s):  
IAN D. MCFARLANE
Keyword(s):  
Electrical Activity ◽  
Conduction System ◽  
Sea Anemones ◽  
Single Shock ◽  
Nerve Net ◽  
Slow Conduction ◽  
Calliactis Parasitica ◽  
Slight Movement ◽  
Pulse Stimulation ◽  
Stimulation Of

1. Single shocks to the column sometimes evoke tentacle contractions, ranging from slight movement of a few scattered tentacles to rapid bending or shortening of all the tentacles. Some individuals are more responsive than others. Complex bursts of electrical activity follow single shocks, but only in tentacles that contract. 2. These single shocks excite pulses in two conducting systems - the through-conducting nerve net (TCNN) and the ectodermal slow conduction system (SSI). When a single shock evokes contractions and bursts of electrical activity, these usually follow the SSI pulse, rarely the TCNN pulse. Stimulation of the SSI alone causes tentacle contraction in responsive anemones. 3. Fast tentacle contractions always follow the second of two closelyspaced TCNN pulses: the TCNN shows facilitation (Pantin, 1935a). An SSI pulse, however, does not facilitate subsequent pulses in either the SSI or TCNN. 4. There are two pathways for activation of tentacle contractions. The TCNN pathway is mechano-sensitive and normally requires facilitation. The SSI pathway is mechano- and chemosensitive, only requires a single SSI pulse to evoke contraction, but is very labile. It is proposed that the TCNN and the SSI do not excite the ectodermal muscles directly, but via a multipolar nerve net.

Control of Preparatory Feeding Behaviour in the Sea Anemone Tealia Felina

1970 ◽  
Vol 53 (1) ◽  
pp. 211-220
Author(s):  
I. D. McFARLANE
Keyword(s):  
Electrical Stimulation ◽  
Feeding Behaviour ◽  
Mouth Opening ◽  
Conduction System ◽  
Sea Anemone ◽  
Feeding Response ◽  
Slow Conduction ◽  
Oral Disk ◽  
Stimulation Of

1. Dissolved food substances elicit preparatory feeding behaviour in the sea anemone Tealia felina. This behaviour takes the form of expansion of the oral disk and lowering of the margin of the disk. Food may also cause mouth opening and pharynx protrusion. This pre-feeding response may increase the chance of food capture. 2. The expansion and lowering of the oral disk can also be elicited by electrical stimulation of a slow conduction system, the SS1, thought to be located in the ectoderm. 3. SS1 activity is seen when the anemone is exposed to dissolved food substances. 4. It is concluded that preparatory feeding behaviour in Tealia is mediated in part by the SS1.

scholarly journals The Nerve-Net of the Actinozoa

1935 ◽  
Vol 12 (2) ◽  
pp. 156-164
Author(s):  
C. F. A. PANTIN
Keyword(s):  
Arbitrary Element ◽  
Primary Response ◽  
Reverse Direction ◽  
Neuromuscular System ◽  
Nervous Systems ◽  
Nerve Net ◽  
Conducting Path ◽  
Synaptic Junctions ◽  
Regular Relation

1. Polarity exists in Calliactis, particularly in the tentacles. In these, there is a centripetal polarity of anatomical origin, but there is in addition a physiological polarity running centrifugally. More stimuli are required to facilitate a conducting path centrally from a point on the tentacle than in the reverse direction. Polarity may originate by the development of differential facilitation rates. 2. In some individuals, a kind of after-discharge is observed. A series of one or more extra contractions follows the primary response to a stimulus. Though these appear only after a stimulus has been given they are only indirectly caused by it. Their presence or absence cannot be predicted and seems to bear no relation to the strength of the stimulus. They introduce an arbitrary element into the otherwise singularly regular relation between stimulus and response. 3. Several possible sources for the phenomenon are considered, including synaptic junctions between conducting units of the nerve net, but there are difficulties in accepting any of them. 4. The nerve net of Calliactis possesses many of the properties of the nervous systems of more highly organised animals. The danger is pointed out of employing the unique skeletal neuromuscular system of the Vertebrata as the standard by which the nervous arrangement of other phyla are to be compared.

scholarly journals Co-Ordination of Pedal-Disk Detachment in the Sea Anemone Calliactis Parasitica

1969 ◽  
Vol 51 (2) ◽  
pp. 387-396
Author(s):  
I. D. MCFARLANE
Keyword(s):  
Electrical Stimulation ◽  
Electrical Activity ◽  
Mechanical Stimulation ◽  
Average Frequency ◽  
Conduction System ◽  
Identical Stimulus ◽  
Slow Conduction ◽  
Calliactis Parasitica ◽  
Behavioural Sequence ◽  
Stimulation Of

1. Electrical activity has been recorded from the sphincter region of Calliactis parasitica during the behavioural sequence in which the anemone detaches from the substrate and attaches to a Buccinum shell. The ectodermal slow-conduction system (SS1) fires repetitively, the majority of observed pulses occurring in the period prior to detachment (a typical example is 25 SS1pulses at an average frequency of 1 pulse/7 sec.). Shell-tentacle contact is essential for stimulation of SS1activity. 2. Mechanical stimulation of the column excites the SS1, and 30 stimuli at a frequency of about one shock/5 sec. give pedal disk detachment. 3. Electrical stimulation of the ectoderm excites the SS1and about 30 stimuli at frequencies between one shock/3 sec. and one shock/9 sec. produce detachment. Detachment and the SS1 have an identical stimulus threshold. It is concluded that detachment is co-ordinated by the SS1.

OCTOPAMINERGIC MODULATION OF THE FOREWING STRETCH RECEPTOR IN THE LOCUST LOCUSTA MIGRATORIA

1990 ◽  
Vol 149 (1) ◽  
pp. 255-279 ◽  
Author(s):  
JAN-MARINO RAMIREZ ◽  
IAN ORCHARD
Keyword(s):  
Intact Animal ◽  
Locusta Migratoria ◽  
Beat Frequency ◽  
Motor Pattern ◽  
Stretch Receptor ◽  
Maximal Effect ◽  
Naturally Occurring ◽  
Entire Central Nervous System ◽  
Dorsal Unpaired Median ◽  
Stimulation Of

Modulatory actions of various biogenic amines and peptides on the locust forewing stretch receptor (SR) were examined. The response of the SR to sinusoidal wing movements was unaffected by physiological concentrations (5×10−8moll−1) of the peptides AKHI, AKHII, proctolin and FMRFamide. The biogenic amine octopamine, however, enhanced the SR response in a dosedependent manner when injected into the haemolymph of an almost intact animal or perfused over an isolated thorax preparation in which head, abdomen, gut and the entire central nervous system were removed (threshold at 5×10−8moll−1, maximal effect at 5×10−4moH−1 DL-octopamine). The SR was as sensitive to D-octopamine, the naturally occurring isomer of octopamine, as it was to DLoctopamine. Serotonin was equal to octopamine in effectiveness, followed in order of potency by synephrine, metanephrine and tyramine. Dopamine was ineffective. Phentolamine, but not DL-propranolol, antagonized the action of octopamine. The threshold of the modulatory effect of octopamine on the SR suggests that the increased haemolymph octopamine level which occurs during flight is sufficient to increase the SR activity. Two observations suggest that dorsal unpaired median (DUM) cells are involved in the octopaminergic modulation of the SR during flight: (1) selective stimulation of these cells modulated the SR response and this effect was blocked by phentolamine; and (2) a number of DUM cells were activated during flight. These results suggest that the SR activity is enhanced by octopamine following the onset of flight. Since the SR is involved in the control of wing beat frequency, the modulation of the SR might influence the generation of the motor pattern in flying locusts.

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.

Control of the Pacemaker System of the Nervenet in the Sea Anemone Calliactis Parasitica

1974 ◽  
Vol 61 (1) ◽  
pp. 129-143
Author(s):  
I. D. MCFARLANE
Keyword(s):  
Sensory Feedback ◽  
Pulse Frequency ◽  
Pulse Number ◽  
Pulse Action ◽  
Conduction System ◽  
The Body ◽  
Optimum Frequency ◽  
Nerve Net ◽  
Slow Conduction ◽  
Calliactis Parasitica

1. The rhythm of spontaneous nerve-net pulses is reset by intercalated evoked nerve-net pulses. 2. The origin of spontaneous nerve-net pulses can shift during a burst. There seem to be many potential pacemakers, widely distributed throughout the body, but apparently absent from the tentacles. 3. If a spontaneous or evoked pulse in the endodermal slow conduction system (SS 2) occurs during a burst, the nerve-net pulse intervals are increased during a 15-30 sec period following the SS 2 pulse. Additional SS 2 pulses cause a further increase in pulse intervals. 4. Nerve-net bursts are followed by a sequence of muscular contractions. The size of the contraction shown by any muscle group depends on nerve-net pulse number and frequency, the optimum frequency being different for different muscles. It is suggested that the SS 2 pulse action on nerve-net pulse frequency can significantly alter the behavioural output of nerve-net bursts. The SS 2 activity may represent sensory feedback on to the nervous pacemakers.

Expansion and Contraction of the Oral Disc in the Sea Anemone Tealia Felina

1972 ◽  
Vol 57 (3) ◽  
pp. 633-649
Author(s):  
I. D. MCFARLANE ◽  
I. D. LAWN
Keyword(s):  
Recovery Period ◽  
Stimulus Frequency ◽  
Sensory Response ◽  
Frequency Range ◽  
Oral Disc ◽  
Nerve Net ◽  
Slow Contraction ◽  
Slow Onset ◽  
Radial Muscle ◽  
Stimulation Of

1. Electrical stimulation of the SS 1 of Tealia felina causes inhibition of spontaneousactivity and increase in length of oral disc radial muscle preparations. This response is elicited over a wide stimulus frequency range (1 every 2 sec to 1 every 30 sec). The response shows a slow onset and a long recovery period. 2. Stimulation of the nerve net at frequencies between 1 shock every 5 sec and 1 shock every 20 sec produces slow contraction. The radials also show fast contractions to shocks less than 2 sec apart. 3. Dissolved food substances excite the SS 1 in the column. The sensory response to application of food extract to a small area of the column shows evidence of sensory adaptation. 4. These observations are related to the pre-feeding response of Tealia and a model for oral disc expansion is described.

Unmyelinated nociceptors of rat paraspinal tissues

1995 ◽  
Vol 73 (5) ◽  
pp. 1752-1762 ◽  
Author(s):  
G. M. Bove ◽  
A. R. Light
Keyword(s):  
Lumbar Spine ◽  
Intact Animal ◽  
Receptive Fields ◽  
Clinical Importance ◽  
Mechanical Stimuli ◽  
Peripheral Neuropathies ◽  
Deep Tissue ◽  
Surrounding Connective Tissue ◽  
Thermal Stimuli ◽  
Stimulation Of

1. We made recordings from rat dorsal root filaments to study unmyelinated afferent units (conduction velocity < or = 1.5 m/s) associated with deep paraspinal tissues of the dorsal sacrum and proximal tail. Data from 57 unmyelinated units were analyzed in 47 experiments. Receptive fields were identified in intact animals and then surgically isolated using microdissection. Units were characterized using mechanical, noxious chemical, and thermal stimuli. 2. These recordings revealed innervation of the nerve sheaths and surrounding connective tissue, muscles, tendons, and tissue apposed to the undersurface of the skin. No units were found with receptive fields directly on joint capsular tissue. The receptive fields of the units were often multiple and located in more than one tissue; 31 of 57 units showed convergence from different tissues. 3. The units with receptive fields on neurovascular bundles shared sensitivities with other deep tissue units described in this and other reports. These units may have clinical importance in pain due to peripheral neuropathies. 4. The units initially responded to strong mechanical stimulation of the intact animal and often to noxious stretch of the tail. Once surgically isolated, an individual unit's threshold to mechanical stimuli appeared lower. 5. Capsaicin (0.001%-0.1%) elicited responses in 81% (17 of 21) of the units tested. Bradykinin (20 micrograms/ml) elicited responses in 45% (10 of 22) of the units tested. Noxious cold (4-10 degrees C) and hot (55 degrees C) stimulation elicited discharges from 33% (5 of 15) and 25% (5 of 20) of the units tested, respectively. 6. The unmyelinated units had similar mechanical, chemical, and thermal sensitivities. These similarities and the observed convergence only allowed separation of units by the tissue in which the ending was found, and did not allow further classification. 7. The prevalence of background discharge suggested that many units were sensitized during the experiments. 8. The sensitivities of these paraspinal units were similar to those reported for other tissues. Because of the anatomic similarity of the paraspinal tissues of the proximal tail and the lumbar spine, the conclusions of the present study can be related to the lumbar spine. These afferent units are thought to participate in nociception from the deep paraspinal tissues.

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