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 Reflex conduction in the giant fibres of the earthworm

1946 ◽  
Vol 133 (870) ◽  
pp. 109-120 ◽  
Keyword(s):  
Nerve Cord ◽  
Sensory Nerves ◽  
The Other ◽  
Reverse Direction ◽  
Middle Region ◽  
Giant Fibre ◽  
Shortening Reaction ◽  
End To End ◽  
The Difference ◽  
Giant Fibres

The present work confirms the conclusion of Friedländer and others that the giant fibres mediate the end-to-end shortening reaction in the earthworm. The chief concern has been to investigate Stough’s claim that the median giant fibre conducts impulses only in the direction from head to tail and the lateral giants only in the reverse direction. Two methods have been employed. ( a ) The nerve cord was exposed at each end of the worm, and electrical records taken simultaneously from the two extremities when the surface of the worm was touched at different places. The results were usually a train of impulses in one or other giant fibre, and it was found that whenever an impulse appeared at one end of a given fibre, it always appeared at the other end of the same fibre. Each fibre, therefore, when it conducted at all, always conducted in both directions. Sensory nerves from the head appeared only connected to the median giant, since stimulation anterior to the clitellum never resulted in lateral fibre activity. Similarly, the tail appeared only to join with the lateral giant fibres. ( b ) Stough’s own method was used, and his observations confirmed, extended and re-interpreted. Either the median or both lateral fibres were divided in one segment. The success of this operation could be judged by leading off the giant fibre responses from the undissected worm (figure 5). Next day, when the worm had recovered, the shortening reflex was observed when the worm was touched at the head, the tail, or in the middle. The shortening was either throughout, or was arrested at the operation site, depending upon whether the active giant fibre was the intact or the damaged one. The results are summarized on p. 119. From both the head and the tail Stough’s observations are confirmed, and it is agreed that impulses from the head are conducted back by the median giant alone. The absence of impulses in the laterals might be due to contrary one-way conduction as Stough assumes, or to the absence of their sensory connexion with the head. But ( a ) above shows that the latter is correct, and the same must be concluded from touching the middle region of the worm, which apparently Stough did not do, for this part connects with the lateral giants, and thus affords a demonstration that these fibres may also conduct antero-posteriorly. The difference in function of the separate giant fibres, therefore, is probably related to their difference in sensory distribution.

Memoirs: The Giant Nerve Fibres and Epistellar Body of Cephalopods

1936 ◽  
Vol s2-78 (311) ◽  
pp. 367-386
Author(s):  
JOHN Z. YOUNG
Keyword(s):  
General Structure ◽  
Stellate Ganglion ◽  
Giant Cells ◽  
Neurosecretory Cells ◽  
Muscular Weakness ◽  
Nerve Fibres ◽  
Giant Fibre ◽  
Giant Fibres ◽  
Number Of Cells ◽  
Small Nerve

1. In Decapod Cephalopods there is a system of giant fibres probably serving to produce the rapid contractions of the mantle muscles and ink-sac by means of which the animal shoots backwards behind a cloud of ink. 2. The giant fibres in the stellar nerves arise in the stellate ganglion, not from single giant cells, but as syncytia, by the fusion of the processes of a large number of cells. In Loligo forbesi all the cells giving rise to the giant fibres of the stellate ganglion are connected together into a giant fibre lobe. 3. In Octopods there are no giant fibres, but in the position of the giant fibre lobe there is a small closed vesicle, pigmented yellow in some species, and named the epistellar body. 4. In the walls of this body there are curious cells, the neurosecretory cells, whose general structure resembles that of neurons, but whose inner processes (axons) end blindly, embedded in a homogeneous substance which fills the cavity. 5. The neurosecretory cells are innervated by a small nerve which reaches them from the mantle connective. 6. After removal of both epistellar bodies from Eledone moschata the animal shows general muscular weakness for some days. 7. It is suggested that the epistellar body has arisen from the giant fibre lobe, and that the neurosecretory cells produce at their inner ends a secretion which is poured into the bloodstream.

scholarly journals Fused neurons and synaptic contacts in the giant nerve fibres of cephalopods

1939 ◽  
Vol 229 (564) ◽  
pp. 465-503 ◽  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Giant Cells ◽  
Nerve Cells ◽  
The Body ◽  
Complete Fusion ◽  
Nerve Fibres ◽  
Giant Fibre ◽  
The Central Nervous System ◽  
Giant Fibre System

The fact that there are two very large nerve cells in the central nervous system of the squid, Loligo , was discovered by Williams (1909), who also gave a brief description of their connexions. His account appears never to have been amplified, or indeed even mentioned, by any subsequent worker until these enormous nerve fibres were accidentally rediscovered in 1933 (see Young 1935 a , 1936 a, b, c ). Williams considered that the whole giant-fibre system on each side of the body consists of the processes of one of the two main giant cells. In fact the arrangement is much more complicated than this, and contains two curiously opposite features of the greatest interest for the neurologist (Young 1936 £). First, the processes of the two main giant cells provide a clear case of the complete fusion of the axons of two nerve cells, thus infringing the strict canon of the neuron theory. Nevertheless, and this is the second point, there are also present, elsewhere in the system, discontinuous synapses which are perhaps more clear and easy to study than any yet described.

THE HISTOLOGY OF THE GIANT FIBRE SYSTEM IN THE ABDOMINAL VENTRAL NERVE CORD OF THE DESERT LOCUST

1970 ◽  
Vol 102 (9) ◽  
pp. 1163-1168 ◽  
Author(s):  
W. D. Seabrook
Keyword(s):  
Single Cell ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Schistocerca Gregaria ◽  
Desert Locust ◽  
Giant Fibre ◽  
Metathoracic Ganglion ◽  
Giant Fibres ◽  
Giant Fibre System

AbstractSchistocerca gregaria possess four neurones of giant fibre proportions within the abdominal ventral nerve cord. These fibres arise from single cell bodies in the terminal ganglionic mass and pass without interruption to the metathoracic ganglion. Fibres become reduced in diameter when passing through a ganglion. Branching of the giant fibres occurs in abdominal ganglia 6 and 7.

The Giant Nerve-Fibres in the Central Nervous System of Myxicola (Polychaeta, Sabellidae)

1948 ◽  
Vol s3-89 (5) ◽  
pp. 1-45
Author(s):  
J.A. C. NICOL
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Nerve Cord ◽  
Size Structure ◽  
Nerve Cells ◽  
The Body ◽  
Usual Sense ◽  
Fibrous Sheath ◽  
Giant Fibre ◽  
The Central Nervous System

1. A description is given of the main features of the central nervous system of Myxicola infundibulum Rénier. 2. The nerve-cord is double in the first four thoracic segments and single posteriorly. It shows segmental swellings but is not ganglionated in the usual sense in that nerve-cell accumulations are not related directly to such swellings of the cord. 3. A very large axon lies within the dorsal portion of the nerve-cord and extends from the supra-oesophageal ganglia to the posterior end of the animal. It is small in the head ganglia where it passes transversely across the mid-line, increases in diameter in the oesophageal connectives, and expands to very large size, up to 1 mm., in the posterior thorax and anterior abdomen, and gradually tapers off to about 100µ in the posterior body. It shows segmental swellings corresponding to those of the nerve-cord in each segment. It occupies about 27 per cent, of the volume of the central nervous system and 0.3 per cent, of the volume of the animal. The diameter of the fibre increases during contraction of the worm. 4. The giant fibre is a continuous structure throughout its length, without internal dividing membranes or septa. Usually a branch of the giant fibre lies in each half of the nerve-cord in the anterior thoracic segments and these several branches are continuous with one another longitudinally and transversely. 5. The giant fibre is connected with nerve-cells along its entire course; it arises from a pair of cells in the supra-oesophageal ganglia, and receives the processes of many nerve-cells in each segment. There is no difference between the nerve-cells of the giant fibre and the other nerve-cells of the cord. 6. A distinct fibrous sheath invests the giant fibre. A slight concentration of lipoid can be revealed in this sheath by the use of Sudan black. 7. About eight peripheral branches arise from the giant fibre in each segment. They have a complex course in the nerve-cord where they anastomose with one another and receive the processes of nerve-cells. Peripherally, they are distributed to the longitudinal musculature. 8. Specimens surviving 16 days following section of the nerve-cord in the thorax have shown that the giant fibre does not degenerate in front of or behind a cut, thus confirming that it is a multicellular structure connected to nerve-cells in the thorax and abdomen. 9. It is concluded that the giant fibre of M. infundibulum is a large syncytial structure, extending throughout the entire central nervous system and the body-wall of the animal. 10. The giant fibre system of M. aesthetica resembles that of M. infundibulum. 11. Some implications of the possession of such a giant axon are discussed. It is suggested that its size, structure, and simplicity lead to rapid conduction and thus effect a considerable saving of reaction time, of considerable value to the species when considered in the light of the quick contraction which it mediates. The adoption of a sedentary mode of existence has permitted this portion of the central nervous system to become developed at the expense of other elements concerned with errant habits.

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 Action potentials from the isolated nerve cord of the earthworm

1945 ◽  
Vol 132 (869) ◽  
pp. 423-437 ◽  
Keyword(s):  
Nerve Cord ◽  
Action Potentials ◽  
Giant Fibre ◽  
Active Structures ◽  
Giant Fibres

Though a great deal of work has been done upon the earthworm, the only investigation of giant fibre activity in the isolated nerve cord appears to be that of Eccles, Granit & Young (1933). As this account is only two pages long and contains no records, it seemed worth while to repeat the work, and § A gives in full my evidence, which supports their conclusions, and doubtless is what they have already observed. Their identification of the active structures with particular giant fibres was rather convincingly inferred, and this has now been confirmed by direct micromanipulation as described in § B.

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. 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.

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.

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