How to use Ganglia in a sentence
The eyes are indicated as black dots behind the cerebral ganglia.
In the region of the neck lateral strands pass through the transverse canal of the cervical vertebrae; but from the thoracic region onwards, where the cardiac branch to the heart is given off, each strand is double and the basal ganglia are successively connected with the next by a branch which runs ventrally over the capitulum of the rib, and by another which passes directly through the foramen or space formed between capitulum and tuberculum.
The nervous system is remarkably concentrated in some beetles, the abdominal ganglia showing a tendency to become shifted forward and crowded together, and in certain chafers all the thoracic and abdominal ganglia are fused into a single nervecentre situated in the thorax, - a degree of specialization only matched in the insectan class among the Hemiptera and some muscid flies.
In all Chaetopods this system consists of cerebral ganglia connected by a circumoesophageal commissure with a ventral ganglionated cord.
The cerebral ganglia constitute an archicerebrum for the most part, there being no evidence that, as in the Arthropoda, a movement forward of post-oral ganglia has taken place.Advertisement
In the latter, the segmentally arranged ganglia are more sharply marked off from the connectives than in other Chaetopods, where nerve cells exist along the whole ventral chain, though more numerous in segmentally disposed swellings.
The nervous system is embedded in the epidermis, and the pairs of ganglia are separated as in Serpula, &c.; each pair has a longish commissure between its two ganglia.
The ganglia are crowded at the posterior end of the body as in leeches, and there is much tendency to the obliteration of the coelom as in that group. Pterodrilus and Cirrodrilus bear a few, or circles of, external processes which may be branchiae; Bdellodrilus and Astacobdella have none.
The most reliable test appears to be the nerve ganglia, which are more distinct from the intervening connectives than in other Annelids.
In the middle of the body, where the limits of the somites can be checked by a comparison with the arrangement of the nephridia and the gonads, and where the ganglia are quite distinct and separated by long connectives, each ganglion is seen to consist of six masses of cells enclosed by capsules and to give off three nerves on each side.Advertisement
An teriorly and posteriorly separate ganglia have fused.
The brain con sists not only of a group of six capsules corre sponding to the archi cerebrum of the Oligo chaeta, but of a further mass of cells surrounding S S and existing below the alimentary canal, which can be analysed into five or six more separate ganglia.
So that a leech in which only twenty-seven segments are apparent by the enumeration of the annuli, separate ganglia, nephridia, lines of sensillae upon the body, really possesses an additional seven lying behind that which is apparently the last of the series and crowded together into a minute space.
Each renal organ is a sac lined with glandular epithelium (ciliated cell, with concretions) communicating with the exterior by its papilla, and by ce, Cerebral ganglia.
On the whole the ganglia are strongly individualized in the Pectinibranchia, nerve-cell tissue being concentrated in the ganglia and absent from the cords.Advertisement
The euthyneurous visceral loop is long, and presents only one ganglion (in Aplysia camelus, but two distinct ganglia joined to one another in Aplysia hybrida of the English coast), placed at its extreme limit, representing both the right and left visceral ganglia and the third or abdominal ganglion, which are so often separately present.
Such special irregularities in the development of ganglia upon the visceral loop, and on one or more of the main nerves connected with it, are very frequent.
Our figure of the nervous system of Aplysia does not give the small pair of buccal ganglia which are, as in all glossophorous Molluscs, present upon the nerves passing from the cerebral region to the odontophore.
T h e buccal nerves and ganglia are omitted.
It flattens out short visceral " loop " with its three ganglia and disappears before is lightly-shaded.Advertisement
The brain innervates the eyes and feelers, and must be regarded as a " syncerebrum " representing the ganglia of the three foremost limb-bearing somites united with the primitive cephalic lobes.
The legs, wings and other organs of the trunk receive their nerves from the thoracic and abdominal ganglia, and the fusion of several pairs of these ganglia may be regarded as corresponding to a centralization of individuality.
A The ganglia of the nervous _ Tre system offer some important evidence as to the morphology of the head, and are alluded to below.
The continuous layer of cells from which the nervous system is developed undergoes a segmentation analogous with that we have described as occurring in the ventral plate; there is thus formed a pair of contiguous ganglia for each segment of the body, but there is no ganglion for the telson.
The ganglia become greatly changed in position during the later life, and it is usually said that there are only ten pairs of abdominal ganglia even in the embryo.Advertisement
But the protocerebrum contains the ganglia of the ocular segment in addition to those of the procephalic lobes.
There are other ganglia in addition to those of the ventral chain, and Janet supposes that the ganglia of the sympathetic system indicate the existence of three anterior head-segments; the remains of the segments themselves are, in accordance with this view, to be sought in the XIII.
There are large lacunae in the head in front of the ganglia.
Laterally, the sub-oesophageal ganglia give off (v.) nerves to the ventral mantle, and finally they supply (vi.) branches to the various muscles.
From each of these sub-oesophageal ganglia numerous nerves arise.
The cerebral mass is in Limulus more easily separated by dissection as a median lobe distinct from the laterally placed ganglia of the cheliceral somite than is the case in Scorpio, but the relations are practically the same in the two forms. Formerly it was supposed that in Limulus both the chelicerae and the next following pair of appendages were prosthomerous, as in Crustacea, but the dissections of Alphonse Milne-Edwards (6) demonstrated VI FIG.
The wide divarication of the lateral cords in the prosoma and their connexion by transverse commissures, together with the " attraction " of ganglia to the prosomatic ganglion group which properly belong to hinder segments, are very nearly identical in the two animals.
Lastly the nervous system is well developed and consists of a pair of well-marked and interconnected ganglia placed near the anterior end and dorsal to the oesophagus.
From these ganglia, nerve-tracts provided with ganglion-cells are given off.
The prey is sometimes stung in the neighbourhood of the nerve ganglia, so that it is paralysed but not killed, the grub of the fossorial wasp devouring its victim alive; but this instinct varies in perfection, and in many cases the larva flourishes equally whether its prey be killed or not.
No organs of circulation or respiration are known; but the nervous system is well developed, and consists of a pair of ganglia corresponding with the limbs and connected by longitudinal commissural chords.
Posteriorly beneath the posterior adductors, and covered only by a thin layer of elongated epidermal cells, are the visceral ganglia.
United with these ganglia on the outer sides are the osphradial ganglia, above which the epithelium is modified to form a pair of sense-organs, corresponding to the osphradia of other Molluscs.
In some Lamellibranchs the osphradial ganglia receive nerve-fibres, not from the visceral ganglia, but from the cerebral ganglia along the visceral commissure.
Formerly the posterior pair of ganglia were identified as simply the osphradial ganglia, and the anterior pair as the cerebral, pleural and visceral ganglia united into a single pair.
But it has since been discovered that in the Protobranchia the cerebral ganglia and the pleural are distinct, each giving origin to its own connective which runs to the pedal ganglion.
In them the foot has a flat ventral surface used for creeping, as in Gastropods, the byssus gland is but slightly developed, the pleural ganglia are distinct, there is a relic of the pharyngeal cavity, in some forms with a pair of glandular sacs, the gonads retain their primitive connexion with the renal cavities, and the otocysts are open.
Generally the system is differentiated into ganglia connected by nerve-cords consisting of nerve-fibres only.
At the point of the collar whence the nerve-cords arise are the cerebral ganglia; from these one pair of connectives passes to a pair of pedal ganglia, and another pair of connectives to a pair of pleural ganglia.
There are usually three small ganglia on the course of this visceral commissure, namely, the right and left visceral ganglia and the abdominal.
The perioesophageal nerve-ring of Chaetopoda and Arthropoda is represented, not by the collar first mentioned in the above description, but by the commissures connecting the cerebral and pedal ganglia.
The otocysts are invaginations of the epithelium of the foot, but are innervated from the cerebral ganglia, and the same innervation has been proved in some cases for the osphradia.
The foot has been developed into long processes which have extended in a circle round the mouth; all the ganglia, including the visceral, have been concentrated around the oesophagus.
Later in its action, the drug depresses the intra-cardiac motor ganglia, causing prolongation of diastole and finally arrest of the heart in dilatation.
The nervous system consists of a cerebral ganglion in the head, a conspicuous ventral ganglion in the trunk, and of lateral cornmissures uniting these ganglia on each side.
The cerebral ganglion also gives off a nerve on each side to a pair of small ganglia, united by a median commissure, which have sunk into and control the muscles of the head.
As in other animals there is a minute but extensive nervous plexus, which permeates the whole body and takes its origin from the chief ganglia.
There are no well-marked specialized ganglia in the central nervous system, nerve-cells being distributed uniformly along the cords.
The labial commissure gives off a subradular commissure which also bears two ganglia, these being in close relation to a special sense-organ called the subradular organ, an epithelial projection with nerve-endings, lying in front of the radula and probably gustatory in function.
B, Buccal ganglia (concerned with the odontophore).
The pedal cords anteriorly form a pair of pedal ganglia united by a thick commissure.
There are two closely connected cerebral ganglia, from which arise the usual two pairs of nerve cords.
A small stomatogastric commissure bearing two small ganglia arises from the cerebral ganglia and surrounds the oesophagus.
The body is composed of a large number of segments; the prostomium bears a pair of tentacles; the nervous system consists of a brain and longitudinal ventral nerve cords closely connected with the epidermis (without distinct ganglia), widely separated in Saccocirrus, closely approximated in Protodrilus, fused together in Polygordius; the coelom is well developed, the septa are distinct, and the dorsal and ventral longitudinal mesenteries are complete; the nephridia are simple, and open into the coelom.
It resembles Dinophilus in the possession of a ventral pharyngeal pouch (which bears teeth in Histriodrilus only), the small number of segments, and absence of distinct septa, the absence of a vascular system, the presence of distinct ganglia on the ventral nerve cords, and of small nephridia which do not appear to open internally.
There are no distinct ganglia, but ganglion cells are uniformly distributed along the ventral side of the cord.
There are two pairs of specialized cerebral nerves innervating the praeoral lobe, and provided with peripheral ganglia placed near the termination of the smaller branches.
In 1842 he wrote a thesis in which he announced the discovery of nerve-cells in ganglia.
The pedal ganglia and auditory organs have disappeared with the foot, at all events have never been detected; the cerebral ganglia are very minute, while the parieto-splanchnic are well developed, and constitute the principal part of the nervous system.
According to Spengel, the pair of ganglia near the mouth, variously called labial or cerebral, represent the cerebral pair and pleural pair of a gastropod combined, and the parietosplanchnic pair correspond to the visceral ganglia, the commissure which connects them with the cerebro-pleural representing the visceral commissure.
Each of the visceral ganglia is connected or combined with an olfactory ganglion underlying an area of specialized epithelium, which constitutes the olfactory organ, the osphradium.
The antennules (or first antennae) are almost universally regarded as true appendages, though they differ from all the other appendages in the fact that they are always innervated from the " brain " (or preoral ganglia), and that they are uniramous in the nauplius larva and in all the Entomostracan orders.
The central nervous system is constructed on the same general plan as in the other Arthropoda, consisting of a supra-oesophageal ganglionic mass or brain, united by circumoesophageal connectives with a double ventral chain of segmentally arranged ganglia.
In the primitive Phyllopoda the ventral chain retains the ladder-like arrangement found in some Annelids and lower worms, the two halves being widely separated and the pairs of ganglia connected together across the middle line by double transverse commissures.
In the higher groups the two halves of the chain are more or less closely approximated and coalesced, and, in addition, a concentration of the ganglia in a longitudinal direction takes place, leading ultimately, in many cases, to the formation of an unsegmented ganglionic mass representing the whole of the ventral chain.
In the higher forms, as already mentioned, the antennal ganglia have become shifted forwards and coalesced with the brain.
The pedal ganglia are situated in the middle of the foot.
There is also a stomatogastric system arising from the cerebral ganglia.
Eyes are absent; attached to the pedal ganglia are a pair of otocysts.
They are innervated from the cerebral ganglia.
It consists of ciliated epithelium, beneath which are two ganglia connected with the labial commissure by nerves.
The nervous system consists of a circumoesophageal nerve, with scarcely differ entiated brain, joining below a large ganglionic mass no doubt representing many fused ganglia (B).
It is only in very large doses that it weakens the intracardiac nervous ganglia, slows and weakens the pulse, and dangerously lowers the blood pressure.
Brain large, with two ventral hollow appendages; ventral cords widely divaricated, without distinct ganglia.
It kills by its paralysing effect on the motor ganglia of the heart and on the respiratory centre.
Case 8 Cerebral embolus from atrial myxoma Findings Subtle reduced density in the left basal ganglia on CT.
The autonomic nerve fibers which radiate from the central nervous system to the ganglia of the autonomic nervous system are called preganglionic nerves.
In this chapter, recent advances in understanding the neuropsychology of basal ganglia disorders are described in detail.
Traditionally, the basal ganglia have been associated with motor processes, although recent evidence suggests that they may also subserve parallel cognitive functions.
Ovi ositor gullet and a highly concentrated nervous 4' p system; in addition to the suboesophageal (side view) of Physo- ganglion, there are two thoracic ganglia pus.
Special to the Heteropoda is the high elaboration of the lingual ribbon, and, as an agreement with some of the opisthobranchiate Euthyneura, but as a difference from the Pectinibranchia, we find the otocysts closely attached to the cerebral ganglia.
The nervous system of Helix is not favourable as an example on account of the fusion of the ganglia to form an almost uniform ring of nervous matter around the oesophagus.
A special " sympathetic " system arises by paired nerves from the oesophageal connectives; these nerves unite, and send back a median recurrent nerve associated with ganglia on the gullet and crop, whence proceed cords to various parts of the digestive system.
In addition, some show duplication of the gonads and of their ducts, so that we find both transverse and longitudinal repetition of these organs, without corresponding multiplication of the nervous ganglia mesenchyma, or excretory opening.
Moreover, in many forms, in which in the adult condition there is only a single pair of anterior ganglia and a single pedal connective, a pleural ganglion distinct from the cerebral has been recognized in the course of development.
The sublingual ganglia are not lettered.
In the primitive Phyllopoda, and less distinctly in some other orders, the nerves supplying the antennae arise, not from the brain, but from the circum-oesophageal commissures, and even in those cases where the nerves and the ganglia in which they are rooted have been moved forwards to the brain, the transverse commissure of the ganglia can still be traced, running behind the oesophagus.
In addition to abnormalities in the production or absorption of these chemical messengers, imaging studies indicate that the blood flow and metabolism in a part of the brain called the basal ganglia are abnormally low.
The basal ganglia are groups of nerve cells deep in the brain that control movement as well as emotion and certain aspects of thinking.
In contrast to the low level of blood flow in the basal ganglia, the motor areas in the frontotemporal cortex of the brain show increased levels of activity.
Children diagnosed with Hirschsprung's disease lack nerve cells (ganglia) in the large intestine, severely affecting the wavelike movements that propel material through the colon.
The virus migrates along nerves to an area of regional ganglia (nerve centers) and then typically enters into a latent (sleeping) phase.
Movement is produced and coordinated by several interacting brain centers, including the motor cortex, the cerebellum, and a group of structures in the inner portions of the brain called the basal ganglia.
Both the cerebellum and the motor cortex send information to a set of structures deep within the brain that help control involuntary components of movement (basal ganglia).
The basal ganglia send output messages to the motor cortex, helping to initiate movements, regulate repetitive or patterned movements, and control muscle tone.
Circuits within the basal ganglia are complex.
Within this structure, some groups of cells begin the action of other basal ganglia components and some groups of cells block the action.
A portion of the basal ganglia called the substantia nigra sends electrical signals that block output from another structure called the subthalamic nucleus.
Disruptions in other portions of the basal ganglia are thought to cause tics, tremors, dystonia, and a variety of other movement disorders, although the exact mechanisms are not well understood.
Transplantation of fetal cells into the basal ganglia has produced mixed results in Parkinson's disease and is being researched for application in other movement disorders.
Fetal tissue transplantation-A method of treating Parkinson's and other neurological diseases by grafting brain cells from human fetuses onto the basal ganglia.
Parkinson's disease-A slowly progressive disease that destroys nerve cells in the basal ganglia and thus causes loss of dopamine, a chemical that aids in transmission of nerve signals (neurotransmitter).