Medullated Fibers Research Articles

Histological Study on the Nerve Distribution in the Larynx in Cat

The r. internus of the n. laryngeus superior comiug into the cat's larynx runs through the canal found in the lateral mid-part of the thyroid cartilage and then divides into the ascending and the descending rami, the latter forming the r. communicans communicating with the n. laryngeus inferior and the former, the thicker of the two rami, parting into bundles of varying sizes which run upwards mostly toward the laryngeal side of the epiglottis and partly to the posterior portion of the plica vocalis, whence some finer branches are sent out to the upper portion of the cavum laryngis inferior. These nerve fibres comprise fine vegetative fibres as well as thick sensory fibres and contain large and small ganglia of sympathetic nature in their courses. The sensory fibres contained in the r. communicans finally spread out in the mucous membrane of the cavum laryngis inferior.The n. laryngeus inferior also consists of fine vegetative fibres and thick medullated fibres and accompanying small ganglia in their upward courses passing between the thyroid cartilage and the m. cricothyreoideus, sends out many branches into the laryngeal muscles and besides also a few fine branches composed of vegetative and sensory fibres into the mucous membrane in the lower part of the cavum laryngis inferior.In the laryngeal side of the epiglottis the submucosal and the proprial plexus are very well developed and consequently, this part is best supplied with sensory fibres of all the parts of the laryngeal cavity. Their terminations, however, are somewhat simpler than the same in dog and goat, consisting only of simple branched terminations originated in medium-sized fibres. These terminations, unlike those in man and some animals, rarely end subepithelially, their terminal fibres usually ending in intraepithelial fibres. These terminal fibres are rarely formed of thick fibres as in dog and goat but are usually very fine fibres provided with small knobs, mostly ending sharply or in small knobs in the snperficial layer of the epithelium.The area the second richest in sensory fibres next to the epiglottis is the part of the mucous membrane covering the apex of the arytenoid cartilage behind the plica vocalis. In the mucous membrane of the ventriculus laryngis are found 2 or 3 papillae resembling the taste-budded papillae on the tongue and many sensory fibres run into these papillae too. The thin mucous membrane covering the arytenoid cartilage extending downwards from the rima glottidis is also considerably rich in sensory fibres. The largest part of the plica vocalis except its posterior portion and the mucous membrane of the cavum laryngis inferior adjacent to it are very poor in sensory fibres.The sensory terminations in the dorsal portion of the plica vocalis, somewhat unlike those in the epiglottis, consist more often in subepithelial rather than intraepithelial terminations of simple branched type, of which the terminal fibres slowly taper off into sharp points. The few intraepithelial fibres are formed by fine fibres or sometimes by medium sized fibres nearly devoid of knobs and rarely go up as far as to the superficial layer of the epithelium. The thin mucous membrane covering the arytenoid cartilage in the cavum laryngis inferior also contains rather many simple branched subepithelial and intraepithelial terminations closely resembling those in the posterior portion of the plica vocalis.The part of the mucous membrane beneath the ciliated epithelium in the cavum laryngis inferior shows a very inferior development of the proprial plexus and consequently the sensory fibres here are very small in number. These fibres end in unbranched and simple branched sub- and intraepithelial terminations composed of very fine terminal fibres devoid of knobs.The taste-buds in the cat's larynx are as abundant as in the dog's and goat's larynges, particularly so in the laryngeal side of the epiglottis

On the Nerve Supply of Trachea, Bronchus and Lung in Goat

A few specially mentionable findings on the histology of the respiratory tract of goat are given in the following:In the trachea, a circular smooth muscle layer lies inside of the tracheal glands, in the portion where the paries membranaceus is formed. This muscle layer becomes better developed distalwards and in the distal end part, comes to cover the nearly complete circumference of the trachea outside its mucous membrane. The right and left extrapulmonary bronchi, very short ducts soon replaced by large intrapulmonary bronchial branches, have a fine structure similar to that of the distal end of the trachea, except that the cartilages are circularly divided into many pieces and are arranged intermittently or in 2 or 3 layers.In the small bronchial branches ca. 2mm in diameter, the cartilaginous pieces are reduced both in number and in size, so weak longitudinal mucous folds come into formation and the bronchial glands also decrease abruptly. In the smaller bronchial branches ca. 1mm in diameter, more prominent longitudinal mucous folds are formed and the epithelium becomes a 2-3-rowed ciliated one, but the muscle layer is yet perceptibly developed. In the bronchioli terminales, the epithelium is composed of one layer of ciliated cells and outside the propria, a circular muscle layer is still visible. The bronchioli respiratorii are lined by a one-rowed nonciliated cylindrical epithelium and a small quantity of muscle tissue. Nothing mentionworthy was found in the alveolar ducts or the alveolar sacs.As in the human trachea (HAYASHI), sensory fibres and their terminations derived from the n. vagus are found in the trachea of goat too, but in the latter, their number and size are smaller than in man. The thick medullated sensory fibres end in branced terminations in the muscle layer, but never forming end-plates as seen in man. Their form, however, suggests the possibility that they are so many Type I terminations concerned with the reflex of lowering the blood pressure. The thin medullated fibres run into the propria and end subepithelially in unbranched and simple branched terminations, only a very few running further into the epithelium. In goat's trachea, no such branched intraepithelial terminations as found in the human counterpart were ever found.As in man and other mammals, in goat too, primary, secondary and tertiary plexus are formed in the interpulmonary bronchial branches, though somewhat poorer in development. In the muscle layer are found branched terminations originating in thick myelinated fibres, while in the propria mucosae are seen some unbranched and simple branched terminations formed by thin myelinated fibres. No intraepithelial fibres are found here. The above findings are rather similar to those obtained in dog (SAITO), but the terminations are somewhat poorer in development than those in dog's bronchus and major bronchial branches.Sensory fibres and their terminations are found in the small bronchial branches and even in the bronchioli of goat too, as it was the case with dog (SAITO) and bat (NUMATA). As in dog, these are better developed than in the larger bronchial branches. The sensory fibres are rather large both in number and in size and simple branched terminations are also found here and there, beside the unbranched ones.What is of interest, unbranched and simple branched terminations formed by rather thick medullated fibres are found also in the interalveolar septa of goat, as in those of bat, in a somewhat better development than in the latter.In the interlobular connective tissue of the lung of goat, nerve bundles containing many thick medullated fibres are found running in company with small pulmonary veins. These bundles run further to reach finally the pleura visceralis. The sensory fibres, as in bat, probably end in unbranched or simple branched terminations in the pleura, but I regret I failed in adequately ascertaining their terminal mode.

On the Nerve Supply of Pharynx and Oesophagus of Snapping Turtle

It is of interest that, in the mucous membrane of the pharynx of Japanese snapping turtle, my so-called pharyngeal papillae resembling the lingual papillae may be found in quantity. The epithelium covering them is of an unhornified stratified flat type and the subepithelial connective tissue lacks mucuous glands. Longitudinal mucous folds are in formation in the oesophagus, covered by a stratified cylindrical epithelium and containing intraepithelial mucous glands. The lamina muscularis mucosae is absent; the tunica muscularis consists of an inner layer of longitudinal striated muscle fibres and an outer layer of circular smooth muscle fibres, but the former is formed only in the lateral sides of the oesophageal wall.In the pharyngeal papillae, as in the lingual, well-developed nerve plexus composed of numerous sensory fibres and vegetative fibres is in formation. Small ganglia are found in this plexus as well as well as in the submucosal and the proprial plexus in the vicinity of the papillae. The ganglion cells in these ganglia are of sympathetic nature showing weak multipolarity but many of them are apparently apolar. The vegetative fibres end as always in STOHR's terminal reticula in the pharyngeal mucous membrane of snapping turtle too.No corpuscular or complex branched termination but only unbranched and simple branched terminations were found here. These are formed in the stocks of the pharyngeal papillae usuall beneath their epithelium, and originate mostly in medium-sized medullated fibres. Their terminal fibres run either nearly straight or looped courses and usually end sharply, but not rarely some end in small endknobs. Intraepithelial fibres are demonstrable in a very small number and are very poorly developed, penetrating only as far as into the basal layer of the epithelium before ending.My so-called perioesophageal plexus formed in the adventia of the oesophagus, interestingly enough, contains small ganglia in some places. AUERBACH's plexus rich in ganglia is found between the outer and the inner muscle layers and MEISSNER's plexus in the submucosa, and what is of highest interest is that ganglion cells are found in the MEISSNER's plexus here in a much larger quantity than in man and mammals.It is needless to reiterate that the ganglion cells found in these plexuses are of sympathetic nature as those in the pharyngeal mucous membrane above and here too the fine vegetative fibres participating in the composition of these plexuses form STOHR's terminal reticula as their terminations.A rather large number of thick sensory fibres are found in the plexus of the oesophagus too. Most of these run from the submucosa into the propria and end there, mostly beneath the epithelium. Their terminations comprise no such corpuscular or complex branched types as found in the human oesophagus, but only unbranched and simple branched (chiefly bifurcated) types, as in the pharynx, with terminal branches ending sharply or bluntly but never forming such end-knobs or intraepithelial fibres as found in the pharynx. Thus, the sensory fibres found in the oesophagus of snapping turtle are far poorer than the same in its pharynx, in quantity as well as in terminal mode.

Trigemino-bulbar reflex pathways.

In decerebrate and decerebellate cats stimulation of any division of the trigeminal nerve induces efferent volleys in the VIIth, Xth, XIth and XIIth nerves. Direct stimulation of the face, internal nares and dura mater produces similar volleys. In uncurarized animals similar stimuli cause twitches of face and neck muscles. Slowing of the heart rate may also be induced. Conduction times measured in the brainstem and cranial nerves show that conduction is very rapid in the brainstem to the level of the obex, so that large medullated fibers may be inferred. At the level of the obex a delay of 2–4 msec. occurs, presumably due to synapses and internuncial neurones. Conduction of the volleys in the Xth and XIth nerves is rapid and large fibers must be involved. Removal of the dorsal vagal nuclei does not abolish the vagal reflex which is presumed to relay at the nucleus ambiguus. The vagal responses are very easily fatigued.

The functional characteristics of the myelinated fibers of the splanchnic nerves

It is experimentally proved that all the large and middle medullated fibers, as well as about a half of the find medullated fibers belong to the afferent fibers of nervi splanchnici majores. To the effereat fibers of nervi splanchnici majores belong about a half of the fine medullated fibers contained in these nerves.

Innervation, Especially, Sensory Innervation of Urethra in the Distal Part of Pig Penis

The nerves penetrating into the mucous membrane of pars cavernosa urethrae in pig comprise a large number of thin medullated fibres and a small number of thick medullated fibres, including also a few vegetative nerve fibres.The termination of vegetative fibres is represented by STOHR's terminalreticulum also in pig urethra.The sensory nerve fibres and their terminations in pig urethra are far below in evolution in comparison with those in human urethra. The genital nerve bodies type III can be mentioned first as the sensory endings not rarely found in pig urethra. They originate from thick medullated fibres and are formed in the periphery of the lamina propria mucosae in main.Branched terminations are also not rare and these are composed of 2 or 3 branches only. Unbranched terminations are the most numerous sensory terminations in the urethra. These two types of terminations come from the thin medullated fibres in general, and only rarely from thick fibres.Intraepithelial fibres are in inferior stage of development and are represented by the unbranched type in all cases. These are derived mainly from thin medullated fibres but sometimes from thick medullated fibres.

Nucleus Mesencephalicus Nervi Trigemini in Human Adult

The nucleus mesencephalicus n. trigemini in man consists of many roundish sensory nerve cells with very few processes and a small number of small-sized vegetative nerve cells, in very rare cases containing wandering motor cells presumably from the nucleus n. trochlearis. The nerve bundle connected with this nucleus is composed of thick medullated fibres and thin unmedullated fibres. The superior fibres, which finally merge with the fasciculus longitudinalis medialis, seem to be represented by the long processes of the nerve cells in this nucleus, i.e. sensory and vegetative fibres, while the inferior fibres, which finally attain the outside of the motor nucleus n. trigemini, apparently consist of sensory fibres coming into the nucleus mesencephalicus from the ganglion Gasseri, and vegetative nerve fibres either from the vegetative cells in this nucleus or other external vegetative fibres running into the nucleus.

On the histology of ductulus lacrimalis in adult, especially on its innervation.

The vertical duct of the ductulus lacrimalis has a non-cornificated flattened stratified epithelium like the margo palpebralis, which is, however, about twice as thick as the epithelium of the latter. The subepithelial fibrous tissue shows for the epithelium scarcely formation of papillae. This fact indicates that this mucous membrane is not so favoured with sensory nerve fibres. The transversal duct of the ductulus shows in the lamina propria the formation of lymphatic tissue, especially near the opening into the lacrimal sac remarkably. Next, the changingg of. the epithelium is noticeable. That is in the stratified flattened epithelium appears the stratified columnal epithelium sporadically. Besides, near the lacrimal sac we can find the remarkably thin columnal epithelium represented by only 2 or 3 layers of epithelial cells, being penetrated by many of lymphocytes. Thirdly comes the bud- or fungi-formed thickning of the mucous membrane strongly projecting into the lumen of-the duct, filled with the well-developed lymphatic tissue and having the epithelium of thin stratified columnal nature. This formation might be thought to exist in order to let the lymphocytes display their duty in full to catch the harmful objects. The weak nerve plexus in tela submucosa is composed of many medullary sensory and a few non-medullated vegetative fibres. The latter finally become to the terminalreticulum and distribute widely in the subepithelial tissue, while the former terminate mainly in lamina propria with various terminations, which are divided roughly into the unspecific or non-contorted and the specific or contorted terminations. The sensory fibres of the non-contorted terminations are mostly composed of medium thick fibres, but rarely of strong fibres, show in general the equality of thickness and terminate sharply or dully direct beneath the epithelium or in direct contact with the basis of the epithelium. The terminations are according to their complexity subdivided into the unbranched and the branched terminations, furthermore the latter into the simple and the complicated forms. The contorted terminations. are seen only in ductulus lacrimalis and margo palpebralis (Seto).9) Their sensory fibres are mostly strong medullated fibres, being often accompanied by small medullated fibres, represent scarcely the variety of thickness and pass into irregular looping terminal formations containing special nuclei here and there. The terminations are further divided into the simple and the complicated forms according to their scale. The former are mostly found in the vertical duct, the latter chiefly in the transversal duct. Some of the specific terminations are represented as the simple glomerular formations, though a few. Besides, as a kind of the specific terminations sometimes exist the unformed terminations composed of strong fibres rich in variety of thickness and showing not so evident winding course, too.

Intestinal Pain: An Electrophysiological Investigation on Mesenteric Nerves

Summary.Afferent impulses from the abdominal viscera have been recorded from the splanchnic nerve and from fine strands of mesenteric nerves of the cat. The Pacinian corpuscles of the exposed mesentery were found to be extremely sensitive to the most gentle pressure, such as faint puff of air.The small intestine very rarely receives any large medullated fibres, and light mechanical stimuli such as slight pressure or touch do not give rise to any inflow of impulses. Fast impulses can be elicited only from those parts of the mesentery possessing Pacinian corpuscles.Injurious stimuli such as pinching applied to the intestinal wall as well as to the mesentery produce δ‐ and C‐potentials. In addition to this, intense stimulation gives rise to large potentials waves apparently built up by slow C‐potentials.It is thus concluded that nociceptive reactions from the intestine are not produced by afferent fibers belonging to the α‐or β‐group but by δ‐ and C‐fibers only.Support is given for the view that the intestinal wall is supplied by afferent fibers able to produce nociceptive reactions in response to such mechanical stimuli which if applied to the skin, would elicit nociceptive reflexes. The sensibility of the intestine itself is thus to be looked upon as very much the same as that of the skin deprived of its fast‐conducting afferent fibers, which respond to vibratory and light mechanical stimuli as well as to stronger pressure.

INTERACTION OF MEDULLATED FIBERS OF A NERVE TESTED WITH ELECTRIC SHOCKS

ArticleINTERACTION OF MEDULLATED FIBERS OF A NERVE TESTED WITH ELECTRIC SHOCKSEdgar A. Blair, and Joseph ErlangerEdgar A. BlairFrom the Physiological Department, Washington University School of Medicine, Saint Louis, and Joseph ErlangerFrom the Physiological Department, Washington University School of Medicine, Saint LouisPublished Online:30 Nov 1940https://doi.org/10.1152/ajplegacy.1940.131.2.483MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation More from this issue > Volume 131Issue 2November 1940Pages 483-493 Copyright & PermissionsCopyright © 1940 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1940.131.2.483History Received 4 August 1940 Published online 30 November 1940 Published in print 30 November 1940 Metrics

On the Autonomic Nervous System of the Teleostean Fish Uranos copus scaber

ABSTRACT The sympathetic ganglia of Uranoscopus resemble those of mammals in that they are connected with the spinal nerves by white rami consisting of medullated (pre-ganglionic) fibres, and grey rami of non-medullated (post-ganglionic) fibres. The sympathetic ganglia are connected together by a chain in which the medullated fibres may run forwards or backwards and may also cross in transverse commissures to the opposite chain. No sympathetic nerves to the heart were found. The cardiac nerves spring from the vagus and consist of medullated fibres. The gonads and the mesonephros and its derivatives (kidneys, urinary bladder) receive nerves only from the sympathetic system, with the exception of the sphincters round the external openings of the gonads and bladder which are innervated by branches of the spinal nerves. There is, on each side, only a single anterior splanchnic nerve from the sympathetic system to the gut; there is therefore nothing corresponding to the pelvic nerves (sacral parasympathetic outflow) of Tetrapods. The sympathetic chain extends into the head and bears sympathetic ganglia in connexion with the vagus, glossopharyngeus, facialis, and trigeminus nerves. The rami communicantes between these sympathetic ganglia and the cranial nerves consist almost entirely of non-medullated (post-ganglionic) fibres; the pre-ganglionic fibres for these ganglia run out in the white rami of the third and fourth spinal nerves and thence forwards in the sympathetic chain. The ciliary ganglion resembles that of mammals, receiving fibres from the trigeminal sympathetic ganglion (radix sympathica), profundus ganglion (radix sensoria) and oculomotor (radix brevis). The sympathetic fibres in the long and short ciliary nerves (though post-ganglionic) are medullated. There is a bundle of fibres running from the trigeminal sympathetic ganglion via the radix longa and radix brevis to the oculomotor nerve. There is a separate profundus ganglion in Uranoscopus from which a small nerve passes to join the trigeminus (portio ophthalmica profundi?) while larger branches run to the long and short ciliary nerves.

DEMONSTRATION OF SPECIAL PARASYMPATHETIC NERVEFIBRES IN THE DORSAL OR POSTERIOR ROOTS OF THE LUMBAR REGION OF THE SPINAL CORD

The commonly received hypothesis that the vaso‐;dilator effects seen on stimulation of the dorsal roots of the spinal nerves in the thoraciclumbar regions of the cord are produced by antidromic impulses passing down the sensory fibres of those roots is incorrect.Evidence is adduced of the presence of numerous fine medullated fibres in the dorsal roots which have their origin in small nerve‐cells in the grey matter at the base of the dorsal horn of the cord, the axis‐cylinders of which pass as fine medullated fibres into the dorsal roots (accompanying the entering sensory fibres), and pass into the dorsal root ganglia. They are there connected by synapse with special nerve‐cells from which other fine medullated fibres come off. These emerge from the ganglion and pass peripherally into the mixed nerve and its branches. Histological examination of the nerve‐fibres of the dorsal roots after section both beyond the ganglion and between the ganglion and the cord affords clear evidence of the above statement. This evidence is obtained from the result of section of the dorsal root between the ganglion and the cord in producing or in failing to produce Wallerian degeneration of the nerve‐fibres in question in the parts of the severed root distal or proximal to the cord respectively, and in the observation of the changes which occur in certain cells of the cord after such section.It is concluded that the centrifugal small medullated fibres in question represent the parasympathetic fibres of the autonomic system of Langley in the thoraciclumbar region of the cord, and that their presence is sufficient to account for the so‐called “antidromic” impulses, which have been supposed to travel (centrifugally) down the sensory nerve‐fibres.

VII. Development of the sympathetic nervous system mammals

The Mammalian sympathetic nervous system presented apparently insurmountable obstacles to both anatomists and physiologists till the publication of Gaskell’s Monograph in 1885 (1). Our knowledge of its structure and functions is now, however, placed on a much firmer basis; and it is possible to enter seriously into a consideration of its morphology and development. A. Physiology . The cells composing the ganglia in the main sympathetic chain are shown by Gaskell to be trophic only. They are neither automatic nor reflex in their action, but merely nourish the fibres which pass from them centrally or peripherally. The gray Rami communicantes spring from the ganglia and are distributed as trophic fibres to the roots and trunk of each spinal nerve and their meninges , and the bodies of the vertebræ. In some cases (e.g. fore and hind limbs) the vasomotor fibres reach their destination through these Kami. The white Rami communicantes are only found in two regions. In the Dog between the tenth and twenty-fifth spinal nerves (second dorsal—second lumbar), and in the Kami of the second and third sacral nerves. This corresponds fairly accurately with their distribution in the human subject (2). In both regions they consist of very small medullated fibres ( 1·8 µ to 2·7 µ ). In the anterior region the white Rami pass from the spinal nerves to the ganglia, and there separate into two groups; one set forms vasomotor fibres, which join the ganglia, become connected with the ganglion-cells, and are distributed peripherally as gray fibres, greatly increased in numbers. The other set does not join the ganglia, but, passing over them, forms the nerves distributed in the Splanchnics to the abdominal viscera as viscero-inhibitory fibres. In the Posterior region white Rami arise from the second and third (and in man fourth (2)) sacral nerves which pass over without joining the ganglia; becoming connected with the hypogastric plexus, they are distributed as the Nervi erigentes ( Vaso-inhibitory fibres). They are possibly also viscero-inhibitory .

The Sympathetic Nervous System 1

THE lecturer commenced by giving a short sketch of Bichat's views of the division of life into organic and animal life, and pointed out how that division naturally led to the conception of two separate central nervous systems, the one, the sympathetic, to which all the organic functions are to be referred, the other, the cerebro-spinal, regulating the animal functions. He then pointed out how Remak's discovery of a special kind of nerve-fibre the non-medullated nerves—associated only with the ganglia of the sympathetic system, tended strongly to confirm Bichat's teaching of the existence of two separate central nervous systems in the human body, each of which communicated with the other by means of its own special kind of nerve-fibres; the cerebro-spinal supplying the sympathetic system with white medullated fibres, and the sympathetic supplying the cerebro-spinal with gray or gelatinous non-medullated fibres. He then continued as follows:—