Temperature Acclimation of the Functional Parameters of the Giant Nerve Fibres in Lumbricus Terrestris L

1967 ◽  
Vol 47 (3) ◽  
pp. 481-484
Author(s):  
ANTTI TALO ◽  
KARI Y. H. LAGERSPERTZ
Keyword(s):  
Refractory Period ◽  
Lumbricus Terrestris ◽  
Temperature Acclimation ◽  
Maximum Response ◽  
Nerve Fibres ◽  
Response Frequency ◽  
Giant Fibre ◽  
Absolute Refractory Period ◽  
The Absolute ◽  
Giant Fibres

1. The temperature dependence of the absolute refractory period and of the maximum response frequency was studied in the median and lateral giant fibres of the nerve cord of earthworms acclimated to 13° or 23° C. 2. Compensatory acclimation of the absolute refractory period in the median giant fibre was statistically significant at 6° and 13° C. The temperature coefficient Q10) was significantly lower in cold-acclimated animals. 3. Compensatory acclimation of the maximum response frequency was significant at 6° C. The ratio between the minimum impulse interval and the absolute refractory period was about 2.2. It was unaltered by temperature acclimation.

Fenestration nodes and the wide submyelinic space form the basis for the unusually fast impulse conduction of shrimp myelinated axons

1999 ◽  
Vol 202 (15) ◽  
pp. 1979-1989 ◽  
Author(s):  
K. Xu ◽  
S. Terakawa
Keyword(s):  
Myelin Sheath ◽  
Lumbricus Terrestris ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Giant Fibre ◽  
Nodal Structure ◽  
Impulse Conduction ◽  
Saltatory Conduction ◽  
Giant Fibres ◽  
Myelinated Fibres

Saltatory impulse conduction in invertebrates is rare and has only been found in a few giant nerve fibres, such as the pairs of medial giant fibres with a compact multilayered myelin sheath found in shrimps (Penaeus chinensis and Penaeus japonicus) and the median giant fibre with a loose multilayered myelin sheath found in the earthworm Lumbricus terrestris. Small regions of these nerve fibres are not covered by a myelin sheath and serve as functional nodes for saltatory conduction. Remarkably, shrimp giant nerve fibres have conduction speeds of more than 200 m s-1, making them among the fastest-conducting fibres recorded, even when compared with vertebrate myelinated fibres. A common nodal structure for saltatory conduction has recently been found in the myelinated nerve fibres of the nervous systems of at least six species of Penaeus shrimp, including P. chinensis and P. japonicus. This novel node consists of fenestrated openings that are regularly spaced in the myelin sheath and are designated as fenestration nodes. The myelinated nerve fibres of the Penaeus shrimp also speed impulse conduction by broadening the gap between the axon and the myelin sheath rather than by enlarging the axon diameter as in other invertebrates. In this review, we document and discuss some of the structural and functional characteristics of the myelinated nerve fibres of Penaeus shrimp: (1) the fenestration node, which enables saltatory conduction, (2) a new type of compact multilayered myelin sheath, (3) the unique microtubular sheath that tightly surrounds the axon, (4) the extraordinarily wide space present between the microtubular sheath and the myelin sheath and (5) the main factors contributing to the fastest impulse conduction velocity so far recorded in the Animal Kingdom.

Temperature Acclimation of the Functional Parameters of the Giant Nerve Fibres in Lumbricus Terrestris L

1967 ◽  
Vol 47 (3) ◽  
pp. 471-480
Author(s):  
KARI Y. H. LAGERSPETZ ◽  
ANTTI TALO
Keyword(s):  
Action Potential ◽  
Temperature Dependence ◽  
Conduction Velocity ◽  
Nerve Cord ◽  
Lumbricus Terrestris ◽  
Temperature Acclimation ◽  
Nerve Fibres ◽  
The Difference ◽  
Giant Fibres ◽  
Q10 Values

1. Temperature dependence of the conduction velocity and the duration of the rising and falling phase of action potential was studied in the median and lateral giant fibres of the nerve cord of earthworms acclimated to 13° or 23° C. 2. Compensatory acclimation of the conduction velocity was found at all temperatures studied from 6° to 32° C. However, the effect was statistically significant only at 6° C. 3. The temperature coefficient (Q10) of the conduction velocity was lower at all temperatures for the cold-acclimated animals. The difference was significant only for the temperature interval from 6° to 13° C. 4. The compensatory acclimation of the duration of the rising and falling phases of the spike was statistically significant at 6° and 13° C. The corresponding Q10 values were lower for the cold-acclimated animals. 5. The duration of the falling phase of the action potential showed the most efficient compensatory acclimation of the parameters studied.

scholarly journals XI. The giant nerve cells and fibres of Halla parthenopeia

1909 ◽  
Vol 200 (262-273) ◽  
pp. 427-521 ◽  
Keyword(s):  
Nerve Cord ◽  
Transverse Section ◽  
Giant Cells ◽  
Nerve Cells ◽  
The Other ◽  
Striking Difference ◽  
Nerve Fibres ◽  
Giant Fibre ◽  
Giant Fibres ◽  
And Function

The giant nerve fibres, which form so prominent a feature in the transverse section of the nerve cord of many Annelids, were first observed in these animals by Clapaède in 1861, who, however, regarded them as canals. They were first recognised as nervous elements—“riesige dunkelrandige Nervenfasern”—by Leydig in 1864. Since then their nervous nature has been almost alternately affirmed and denied, and many widely divergent views have been advanced regarding their morphology and function. The connection of giant fibres with certain giant nerve cells was first shown in the case of Halla parthenopeia , by Spengel, in 1881. Although many other workers have investigated these elements, information is still lacking regarding several fundamental points of their structure. For instance, nothing is known regarding the neurofibrillæ of the giant cells, and although these conducting elements have been seen by five observers in the giant fibres of earthworms, there is a striking difference in their accounts: two of them refer to the presence of several neurofibrillæ, while the others describe or figure only a single fibril in each giant fibre. Further, no information is available regarding the place and mode of origin of these neurofibrillæ or their relations to other nerve elements. This defect is, no doubt, due largely to the difficulties attending the investigation of these remarkable cells and fibres; indeed, the failure of the methods usually adopted for staining nerve cells and fibres in other animals, to disclose nervous elements in the giant cells and fibres, has been held, for instance, by yon Lenhossék and Retzius, to disprove their nervous nature. The present investigation was commenced in 1900 with the view of determining the character and arrangement of the neurofibrillæ of the giant cells and fibres and the relations of these elements to the other elements of the nerve cord.

scholarly journals Inotropic Effects of Trains of Impulses Applied during the Contraction of Cardiac Muscle

1960 ◽  
Vol 44 (2) ◽  
pp. 415-432 ◽  
Author(s):  
A. J. Brady ◽  
B. C. Abbott ◽  
W. F. H. M. Mommaerts
Keyword(s):  
Cell Membrane ◽  
Cardiac Muscle ◽  
Direct Effect ◽  
Refractory Period ◽  
Muscle Preparation ◽  
Inotropic Effects ◽  
Absolute Refractory Period ◽  
The Absolute ◽  
Stimulation Of

The application of a train of supramaximal stimuli during the absolute refractory period of a cardiac muscle preparation has two effects: a depression of the contraction during which it is applied, and a large potentiation of subsequent contractions. The former is ascribed to a direct effect upon the cell membrane, and is an indication of the continued control of the contractile event by this membrane. The latter is explained as a sudden liberation of norepinephrine by a stimulation of embedded nerve elements, which norepinephrine then distributes itself through the tissue and finally diffuses away.

The Giant Fibre Reflex of the Earthworm, Lumbricus Terrestris L

1962 ◽  
Vol 39 (2) ◽  
pp. 219-227
Author(s):  
M. B. V. ROBERTS
Keyword(s):  
Nerve Cord ◽  
Lumbricus Terrestris ◽  
The Body ◽  
Muscle Preparation ◽  
Direct Stimulation ◽  
Giant Fibre ◽  
Low Threshold ◽  
Giant Fibres ◽  
Nerve Muscle ◽  
Stimulation Of

1. A nerve-muscle preparation including the longitudinal musculature and the giant fibres in the nerve cord of the earthworm is described. 2. Direct stimulation of the nerve cord with single shocks of increasing intensity results in two types of response: (a) a low threshold, very small twitch, resulting from a single impulse in the median giant fibre, and (b) a higher threshold, slightly larger twitch, resulting from single impulses in the median and lateral giant fibres. Both responses are highly susceptible to fatigue. 3. Stimulation of the body surface evokes a much more powerful contraction which is associated with a burst of impulses in the giant fibre. The strength of the contraction depends upon the number of impulses in the burst and this in turn upon the intensity and duration of the stimulus.

scholarly journals On The Excitation of Crustacean Muscle

1936 ◽  
Vol 13 (1) ◽  
pp. 111-130
Author(s):  
C. F. A. PANTIN
Keyword(s):  
Refractory Period ◽  
Motor Nerve ◽  
Carcinus Maenas ◽  
Motor Units ◽  
Repetitive Stimulation ◽  
Muscle Fibres ◽  
Absolute Refractory Period ◽  
Excitable System ◽  
Crustacean Muscle ◽  
The Absolute

1. The response of certain limb muscles in Carcinus maenas to stimuli of different frequencies and intensities has been analysed. The precautions necessary to obtain reproducible results in crustacean muscle are recorded. The material must be fresh; the duration of stimulation short; and each individual shock must be less than the true chronaxie, to prevent multiple excitation of the nerve. 2. A single stimulus produces a microscopic response or none at all. A succession of shocks, however, causes a contraction, the rate of which increases with the frequency, till this reaches the high values of 300-400 shocks per sec. The rate of contraction varies absolutely continuously with the frequency from 300 per sec. down to the microscopic response observed at less than 10 per sec. The rate of contraction increases very rapidly indeed between frequencies of 50 and 200 per sec, so that this range includes almost all rates of contraction. 3. The limiting frequency of 300-400 per sec. is close to the refractory period. For pairs of stimuli, the absolute refractory period is about 1σ at 18° C. This is followed by a relative refractory phase and sometimes by a supernormal phase. The excitability has returned to normal after about 4σ. In repetitive stimulation the absolute refractory period lengthens. 4. With stimuli of increasing intensity, the responses of both flexor and extensor muscles show first a threshold for excitation of the motor nerve, and, at a higher intensity, a threshold for inhibition. At very high intensities (10-20 times the true threshold) large contractions may be obtained owing to repetitive excitation. 5. With suitable precautions it can be shown that between the threshold of excitation and the threshold of inhibition there is great independence between the response and the intensity of the stimulus. The system behaves as a single excitable system and possibly in some cases a single axon supplies the entire muscle. 6. The chronaxie of the nerve to single shocks and to repetitive stimulation is of the order of 0.2-0.4σ. Single shocks of high intensity give multiple excitation, and the thresholds for this simulate a chronaxie curve. False chronaxies up to 30σ can be obtained in this way. 7. There is no evidence of a double excitable system in the muscles of the walking leg of Carcinus such as has sometimes been recorded in crustacean claws. There is no doubling of intensity-duration or refractory period curves. 8. All the effects observed are explicable in terms of neuromuscular facilitation. The response is governed entirely by the frequency and number of stimuli. Each shock in a series brings more and more muscle fibres into action. With increasing frequency of stimulation, not only are there more contraction increments in a given time, but the increment following each shock is larger. 9. At low and moderate frequencies the rate of development of tension is governed by the rate at which impulses reach the muscle. At the highest frequencies a limit is set to the rate of contraction by the physical properties of the muscle. 10. There is a close analogy between the neuromuscular mechanism disclosed here and the neuromuscular mechanism of the Coelenterata. In both there is a tendency for an entire effector to behave as a single system in which the response is governed by the number and frequency of impulses received by the muscle. This system is distinguished sharply from that of vertebrate skeletal muscle in which gradation of response is brought about through the multiplicity of motor units.

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