The Functioning of the Giant Nerve Fibres of the Squid

1938 ◽  
Vol 15 (2) ◽  
pp. 170-185 ◽  
Author(s):  
J. Z. YOUNG
Keyword(s):  
Threshold Voltage ◽  
Functional Unit ◽  
Repetitive Firing ◽  
Maximal Response ◽  
Muscle Fibres ◽  
Nerve Fibres ◽  
Giant Fibre ◽  
Giant Fibres ◽  
Enormous Number ◽  
Stimulation Of

1. Stimulation of single giant nerve fibres in the stellar nerves of the squid (Loligo pealii) shows them to be motor axons which produce contraction of the circular fibres of the mantle muscles. 2. When a stellar nerve is stimulated with condenser discharges a maximal response is obtained at threshold voltage. No increase of response is obtained by further increase in the strength of stimulation except for an occasional slight increase at about ten times threshold voltage probably due to repetitive firing. It therefore appears that the stimulus produces a single impulse in the giant fibre, and that this is capable of exciting contraction in all the muscle fibres which it reaches. This confirms the conclusion reached on histological grounds that in spite of their syncytial nature each of the giant nerve fibres is a single functional unit. 3. Since there are about ten giant fibres on each side the mantle is divided into 20 neuromotor units, each nerve fibre innervating an enormous number of muscle fibres. The existence of these units can also very readily be demonstrated by the fact that threshold electrical stimulation at any point within the territory innervated by each single giant fibre sets up a contraction of the muscle fibres of all parts of the territory with which the stimulated area is in connexion through the nerve. 4. Stimulation of the smaller fibres in a stellar nerve after destruction of the giant fibre also causes contraction of the circular muscles of the mantle. The amount of this contraction increases progressively with increased voltage, presumably on account of the stimulation of more and more nerve fibres. The maximum tension developed in this way is always very much less than that produced by stimulation of the giant fibres. 5. The mantle is therefore provided with a double mechanism of expiratory contraction, maximal contractions being produced by single impulses in the giant fibres and graded contractions by those in the smaller fibres of the nerve. Presumably the former contractions are those involved in rapid movement, the latter in respiration. 6. There are also radial muscles, running through the thickness of the mantle, whose contractions effect the inspiration by making the cavity larger.

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.

Escape from Recurring Tactile Stimulation in Branchiomma Vesiculosum

1965 ◽  
Vol 42 (2) ◽  
pp. 307-322 ◽  
Author(s):  
FRANKLIN B. KRASNE
Keyword(s):  
Ventral Nerve Cord ◽  
Tactile Stimulation ◽  
The Body ◽  
Direct Stimulation ◽  
Giant Fibre ◽  
Sensory Ending ◽  
Tactile Stimuli ◽  
Escape Reflex ◽  
Giant Fibres ◽  
Stimulation Of

1. Branchiomma's rapid escape from tactile stimuli is mediated by the pair of giant nerve axons which run the length of the body above the ventral nerve cord. 2. The giant neurons are connected by very stable, polarized junctions to giant motor axons. 3. The giant-fibre escape reflex fails if tactile stimuli are repeated; a non-giant system which continues to cause slower escape eventually fails also. 4. Recovery from reflex failure is slow. 5. The failure of the rapid escape reflex occurs prior to the giant fibre. It is not primarily due to sensory ending accommodation. It cannot be caused by direct stimulation of the giant fibres.

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.

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.

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.

scholarly journals The Motor Innervation of a Triply Innervated Crustacean Muscle

1939 ◽  
Vol 16 (4) ◽  
pp. 398-402
Author(s):  
A. VAN HARREVELD
Keyword(s):  
Mechanical Injury ◽  
Muscle Fibres ◽  
Motor Innervation ◽  
Nerve Fibres ◽  
Crustacean Muscle ◽  
Conduction Process ◽  
Slow Contraction ◽  
Stimulation Of

The crustacean muscle is extremely sensitive to mechanical injury. This is due to the fact that the muscle fibres are innervated by a feltwork of nerve fibres which surrounds them. Apparéntly, there is a lack of a muscular conduction process in these muscles. Contractions have been observed in the same muscle fibres during stimulation of the axon for the fast contraction as well as during stimulation of the fibre for the slow contraction.

Analysis of the rapid responses of Nereis and Harmothoë ( Annelida )

1959 ◽  
Vol 150 (939) ◽  
pp. 245-262 ◽  
Keyword(s):  
Longitudinal Muscle ◽  
Electrical Response ◽  
Low Frequency ◽  
Fast Response ◽  
Motor Neurone ◽  
Muscle Fibres ◽  
Giant Fibre ◽  
Rapid Responses ◽  
Giant Fibres ◽  
Nerve Muscle

The giant-fibre responses of Harmothoë and Nereis have been studied with emphasis on the afferent and efferent path ways and the sites of the rapid accommodation of the fast response. When the bundle of sensory neurones of the anal cirrus is stimulated the giant-fibres respond at the first shock. This terminal junction then rapidly accommodates to further afferent excitation. In Harmothoë the muscles which effect the rapid movements of the giant-fibre response are directly innervated by large axons of unipolar cell bodies in the central nervous system. In each segment one neurone of this type supplies both dorsal and ventral longitudinal muscle fibres. By use of a bridge technique this neurone has been isolated. At the first stimulus above a single sharp threshold the resulting nerve muscle preparation gives a maximum electrical response, which is independent of the stimulus strength. A reduced response persists for many repetitions at low frequency. In addition to this fast motor neurone a slower system in the same muscles is indicated by the muscle-action potentials and by observation of the movements. An axon-axon synapse seen histologically between the lateral giant fibres and the large motor neurone to the longitudinal muscle has been identified with the rapidly accommodating physiological junction between these elements. At this level of analysis the afferent and efferent relations of the giant fibres, and in particular the fast motor innervation, are broadly comparable with those of some arthropods.

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.

Reflex Control of Abdominal Flexor Muscles in the Crayfish

1965 ◽  
Vol 43 (2) ◽  
pp. 211-227 ◽  
Author(s):  
DONALD KENNEDY ◽  
KIMIHISA TAKEDA
Keyword(s):  
Giant Axon ◽  
Muscle Fibres ◽  
Motor Axons ◽  
Giant Fibre ◽  
Optimal Interval ◽  
Flexor Muscles ◽  
Muscle Types ◽  
Giant Fibres ◽  
Large Motor ◽  
Almost All

1. The flexor musculature of the crayfish abdomen is divided into two systems: a set of tonic superficial muscles, and a complex series of massive flexor muscles that produce powerful twitches but never exhibit tonic contractions. The muscle types are histologically differentiated, and also separately innervated: the main flexors receive ten large motor axons, and the slow superficial muscles six smaller ones. 2. Fibres of the main flexor muscles studied are almost all triply innervated; each receives endings from (a) the ‘motor giant’ axon, (b) one of several specific non-giant motor axons, and (c) a common inhibitor. 3. Excitatory junctional potentials (e.j.p.s) due to motor giant and non-giant axons are similar and large; each may trigger secondary, active ‘spikes’, thus often producing post-junctional responses of 100 mV. or more. The responses differ in that the motor giant e.j.p. shows a dramatic decrease upon repetitive stimulation, whereas that due to non-giant motor axons exhibits some facilitation. 4. Activity in the central giant fibres drives both motor axons. The response to both, when the motor giant system is fully rested, is slightly larger than that to either alone; when activated by stimulation of the central giant fibre the junctional potentials are evoked asynchronously due to differences in central reflex time, and double spiking in the muscle fibres sometimes results. Upon repeated stimulation the response to the giant is reduced to a very low level; this is accompanied by a decrease in the tension developed in successive reflexly evoked twitches. The motor giant system thus apparently functions to provide additional tension for the first few ‘flips’ in a series of swimming movements during escape. 5. Impulses in the inhibitor axon, even at the optimal interval, reduce the amplitude of excitatory post-junctional potentials by only a small amount; their effect in shortening duration is more notable. It is postulated that the peripheral inhibitor functions to cut short excitatory depolarizations and hence to terminate lingering tension that might oppose subsequent reflex actions.

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