Electrophysiology of the peripheral nerve net in the polyclad flatworm Freemania litoricola

1975 ◽  
Vol 62 (2) ◽  
pp. 469-479
Author(s):  
H. Koopowitz
Keyword(s):  
Action Potentials ◽  
Body Wall ◽  
Contralateral Side ◽  
The Body ◽  
Conducting System ◽  
Response Decrement ◽  
Posterior Portion ◽  
Nerve Net ◽  
Tactile Stimuli ◽  
The Brain

1. A diffuse-conducting system close to the dorsal epithelium of the polyclad flatworm Freemania litoricola is described. Tactile stimuli elicit small action potentials which can be conducted around lesions through the body wall. The potentials can occur in bursts or barrages. 2. This conducting system appears to be insensitive to Mg2+ ions. 3. Conduction velocities (0–26--71 m/sec) vary over the animal. Conduction spread in the anterior half of the animal appears to be greater than that in the posterior portion. 4. Response decrement to repeated stimulation can be recorded in the peripheral system but it is not clear if this is due to habituation or fatigue. 5. Conduction from the peripheral net to the brain occurs. Some central units appear to pick up information only, or mainly, through the anterior nerves, while other units can respond to information conducted through the network to nerves of the contralateral side. 6. Different possibilities to account for this system are discussed, and it is suggested that the animals either possess a unique Mg2+ insensitive synaptic nerve-net or else the network is electrically coupled.

Neurologic Disorders Categorized by Anatomical Involvement

2012 ◽  
Author(s):  
Brian A. Crum ◽  
Eduardo E. Benarroch ◽  
Robert D. Brown
Keyword(s):  
Nervous System ◽  
Cerebral Cortex ◽  
Contralateral Side ◽  
The Body ◽  
Neurologic Symptom ◽  
Visuospatial Deficits ◽  
Neurologic Disorders ◽  
The Brain ◽  
Symptoms And Signs ◽  
Cardiovascular Functions

Neurological disorders of the brain, spine, and peripheral nervous system are examined. Symptoms and signs related to disorders of the cerebral cortex may lead to alterations in cognition and consciousness. Unilateral neurologic symptoms involving a single neurologic symptom commonly localize to the cerebral cortex. Abnormalities of speech and language are localized to the dominant cerebral hemisphere, whereas abnormalities of the nondominant hemisphere may lead to visuospatial deficits, confusion, or neglect of the contralateral side of the body. The hypothalamus is important in many functions that affect everyday steady-state conditions, including temperature regulation, hunger, water regulation, sleep, endocrine functions, cardiovascular functions, and regulation of the autonomic nervous system. Cortical and subcortical abnormalities may also lead to visual system deficits, usually homonymous visual defects of the contralateral visual field. Sensory levels, signs of anterior horn cell involvement, and long-tract signs in the posterior columns or corticospinal tract suggest a spinal cord lesion.

The whole-body withdrawal response of Lymnaea stagnalis. I. Identification of central motoneurones and muscles

1991 ◽  
Vol 158 (1) ◽  
pp. 63-95 ◽  
Author(s):  
G. P. Ferguson ◽  
P. R. Benjamin
Keyword(s):  
Action Potentials ◽  
Lymnaea Stagnalis ◽  
Contralateral Side ◽  
The Body ◽  
Whole Body ◽  
Muscle Fibres ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
Synchronous Contraction ◽  
Withdrawal Response

Two muscle systems mediated the whole-body withdrawal response of Lymnaea stagnalis: the columellar muscle (CM) and the dorsal longitudinal muscle (DLM). The CM was innervated by the columellar nerves and contracted longitudinally to shorten the ventral head-foot complex and to pull the shell forward and down over the body. The DLM was innervated by the superior and inferior cervical nerves and the left and right parietal nerves. During whole-body withdrawal, the DLM contracted synchronously with the CM and shortened the dorsal head-foot longitudinally. The CM and the DLM were innervated by a network of motoneurones. The somata of these cells were located in seven ganglia of the central nervous system (CNS), but were especially concentrated in the bilaterally symmetrical A clusters of the cerebral ganglia. The CM was innervated by cells in the cerebral and pedal ganglia and the DLM by cells in the cerebral, pedal, pleural and left parietal ganglia. Individual motoneurones innervated large, but discrete, areas of muscle, which often overlapped with those innervated by other motoneurones. Motoneuronal action potentials evoked one-for-one non-facilitating excitatory junction potentials within muscle fibres. No all-or-nothing action potentials were recorded in the CM or DLM, and they did not appear to be innervated by inhibitory motoneurones. The whole network of motoneurones was electrotonically coupled, with most cells on one side of the CNS strongly coupled to each other but weakly coupled to cells on the contralateral side of the CNS. This electrotonic coupling between motoneurones is probably important in producing synchronous contraction of the CM and DLM when the animal retracts its head-foot complex during whole-body withdrawal.

The Origin of the Interoceptive Pathway

2014 ◽  
Author(s):  
A. D. (Bud) Craig
Keyword(s):  
Spinal Cord ◽  
Motor Function ◽  
Contralateral Side ◽  
Dorsal Column ◽  
The Body ◽  
Sensory Loss ◽  
Anatomical Basis ◽  
Touch Sensation ◽  
Temperature Sensations ◽  
The Brain

This chapter describes the functional and anatomical characteristics of interoceptive processing at the levels of the primary sensory fiber and the spinal cord. The association of the spinothalamic pathway with pain and temperature had already been described in textbooks for years. The clinical evidence indicated that a knife cut that severed the spinal cord on one side produced a loss of pain and temperature sensations only on the opposite (contralateral) side of the body, as tested with pinprick and a cold brass rod, combined with the loss of discriminative touch sensation and skeletal motor function on the same (ipsilateral) side as the injury to the spinal cord. The anatomical basis for this dissociated pattern of sensory loss is the distinctness of the two ascending somatosensory pathways to the brain-discriminative touch sensation in the uncrossed (ipsilateral) dorsal column pathway, and pain and temperature sensations in the crossed (contralateral) spinothalamic pathway.

Activity and habituation in the brain of the polyclad flatworm Freemania litoricola

1975 ◽  
Vol 62 (2) ◽  
pp. 455-467
Author(s):  
H. Koopowitz
Keyword(s):  
Evoked Potentials ◽  
Spike Activity ◽  
Posterior Part ◽  
Repetitive Stimulation ◽  
Evoked Responses ◽  
Inhibitory System ◽  
Posterior Portion ◽  
Tactile Stimuli ◽  
Vibration Responses ◽  
The Brain

1. A variety of spontaneously active units was measured in the brain of the polyclad flatworm Freemania litoricola. Following application of MgCl2 there was both a decrease in number of active units and a decrease in frequency of firing of those cells which persisted in their activity. 2. Receptors which respond to vibration stimuli evoke potentials in the posterior part of the brain. Repetitive stimulation leads to habituation, the extent of which is dependent on both the number of times stimulated and the strength of the stimulus. Weaker stimuli habituate more rapidly than strong stimuli. Habituated responses can be dishabituated by tactile stimuli and also by stronger intensity stimuli of the same modality. The vibration-evoked potentials appear to occur in at least second-order cells, since vibration responses are abolished by the application of MgCl2. 3. Tactile responses can also be elicited from the posterior portion of the brain when the stimulus is applied to the periphery of the animal. These responses are insensitive to MgCl2. 4. Both vibration and tactile evoked responses are able to evoke further barrages of spike activity. 5. The presence of a dual sensitizing and inhibitory system during habituation is discussed.

scholarly journals Body Representation in Anorexia Nervosa

2021 ◽  
Author(s):  
Anouk Keizer ◽  
Manja Engel
Keyword(s):  
Anorexia Nervosa ◽  
Body Size ◽  
Body Representation ◽  
The Body ◽  
Size Perception ◽  
Tactile Stimuli ◽  
Body Experiences ◽  
Sensory Modalities ◽  
Multisensory Information ◽  
The Brain

Anorexia nervosa (AN) is an eating disorder that mainly affects young women. One of the most striking symptoms of this disorder is the distorted experience of body size and shape. Patients are by definition underweight, but experience and perceive their body as bigger than it in reality is. This body representation disturbance has fascinated scientists for many decades, leading to a rich and diverse body of literature on this topic. Research shows that AN patients do not only think that their body is bigger than reality, and visually perceive it as such, but that other sensory modalities also play an important role in oversized body experiences. Patients for example have an altered (enlarged) size perception of tactile stimuli, and move their body as if it is larger than it actually is. Moreover, patients with AN appear to process and integrate multisensory information differently than healthy individuals, especially in relation to body size. This leads to the conclusion that the representation of the size of the body in the brain is enlarged. This conclusion has important implications for the treatment of body representation disturbances in AN. Traditionally treatment of AN is very cognitive in nature, it is possible however that changed cognitions with respect to body size experiences do not lead to actual changes in metric representations of body size stored in the brain. Recently a few studies have been published in which a multisensory approach in treatment of body representation disturbance in AN has been found to be effective in treating this symptom of AN.

Conduction and coordination in deganglionated ascidians

2000 ◽  
Vol 78 (9) ◽  
pp. 1626-1639 ◽  
Author(s):  
G O Mackie ◽  
R C Wyeth
Keyword(s):  
Body Wall ◽  
Motor Nerve ◽  
Histological Study ◽  
The Body ◽  
Nerve Terminals ◽  
Sea Anemones ◽  
Nerve Net ◽  
Electrophysiological Recordings ◽  
Motor Neurones ◽  
Conduction Of Excitation

The behaviour of Chelyosoma productum and Corella inflata (Ascidiacea) was studied in normal and deganglionated animals. Chelyosoma productum lived for over a year after deganglionation and the ganglion did not regenerate. Electrophysiological recordings were made from semi-intact preparations. Responses to stimulation and spontaneous activity continued to be transmitted through the body wall and branchial sac after deganglionation. Spread was slow, decremental, and facilitative. Treatment with >10 µg·mL-1 d-tubocurarine abolished all responses, indicating that nerves mediate conduction of excitation after deganglionation. Histological study using cholinesterase histochemistry and immunolabelling with antisera against tubulin and gonadotropin-releasing hormone showed no evidence of a peri pheral nerve net in regions showing conduction, contrary to previous claims. The cell bodies of the motor neurones were found to lie entirely within the ganglion or its major roots. Their terminal branches intermingled to form netlike arrays. Sensory neurons were identified with cell bodies in the periphery, in both the body wall and the branchial sac. Their processes also intermingled in netlike arrays before entering nerves going to the ganglion. It is concluded that the "residual" innervation that survives deganglionation is composed of either interconnected motor nerve terminals, interconnected sensory neurites, or some combination of the two. In re-inventing the nerve net, ascidians show convergent evolution with sea anemones, possibly as an adaptation to a sessile existence.

The Blood Vascular System of Nephtys (Annelida, Polychaeta)

1956 ◽  
Vol s3-97 (38) ◽  
pp. 235-249
Author(s):  
R. B. CLARK
Keyword(s):  
Body Wall ◽  
Vascular System ◽  
Close Association ◽  
Circulatory System ◽  
Ventral Surface ◽  
Blood Stream ◽  
Neurosecretory Cells ◽  
The Body ◽  
Dorsal Vessel ◽  
The Brain

The four longitudinal vessels of the circulatory system of Nephtys californiensis are dorsal, sub-intestinal, and neural, the latter being paired. There is a complete longitudinal circulation; the dorsal vessel communicates with the sub-intestinal by way of the proboscidial circulation and with the neural by way of the circum-oral vessels. In each middle and posterior segment segmental vessels from each of the longitudinal trunks carry blood to and from the parapodia and body-wall. The segmental circulation is completed by a circum-intestinal vessel connecting the dorsal and subintestinal vessels in each segment and an intersegmental branch connecting the dorsal and sub-intestinal segmental vessels. A trans-septal branch of the neural segmental vessel communicates with the sub-intestinal segmental vessel. This arrangement is modified in anterior segments which house the muscular, eversible pharynx, and no blood-vessels cross the coelom except by running through the body-wall. On anatomical grounds and by comparison with other polychaetes it seems likely that segmental is subordinate to longitudinal circulation. There are no endothelial capillaries such as have been described in some other polychaetes; instead there are numerous blindending vessels the walls of which are composed of the same three layers as other vessels and which are probably contractile. The dorsal vessel, where it is in contact with the ventral surface of the supra-oesophageal ganglion, forms a plexus in close association with a modified part of the brain capsule and a special axonal tract within the ganglion. It is thought that by way of this ‘cerebro-vascular complex’, hormones produced in the neurosecretory cells of the brain pass into the blood-stream.

A new genus and species of monostiliferous hoplonemertean (Enopla: Hoplonemertea: Monostilifera) from New Zealand

Zootaxa ◽  
2002 ◽  
Vol 50 (1) ◽  
pp. 1 ◽  
Author(s):  
RAY GIBSON ◽  
MALIN STRAND
Keyword(s):  
New Zealand ◽  
Body Wall ◽  
New Genus ◽  
Morphological Features ◽  
The Body ◽  
Full Length ◽  
New Taxon ◽  
New Genus And Species ◽  
The Brain

Vulcanonemertes rangitotoensis gen. et sp. nov. (Hoplonemertea: Monostilifera) is described and illustrated. Major morphological features of the new taxon include an anteriorly divided body wall longitudinal musculature, no pre-cerebral septum, cephalic glands which reach far back behind the brain, and accessory lateral nerves which extend the full length of the body.

A non-fatal method of sex determination for patellacean gastropods

1979 ◽  
Vol 59 (3) ◽  
pp. 803-803 ◽  
Author(s):  
W. G. Wright ◽  
D. R. lindberg
Keyword(s):  
Body Wall ◽  
The Body ◽  
Hypodermic Needle ◽  
Microscope Slide ◽  
Posterior Portion ◽  
Sudden Decrease ◽  
Reproductive Cycles ◽  
Glass Microscope Slide ◽  
Glass Microscope

During our studies of the reproductive cycles in limpets (family Acmaeidae) we have been confronted by the lack of a method to determine sex without killing the animals. Previous studies have relied upon dissection or histological sectioning to determine sex. This note describes a technique which allows the determination of sex in patellacean limpets without killing the animal.The tools needed are a syringe (1 cc) with a hypodermic needle (we have found that a 26 gauge, 16 mm needle works well with specimens larger than 10 mm in length), and a glass microscope slide. After removing the limpet from the substratum the shell is held with the aperture down. As the animal extends its foot downward it exposes and stretches the sides of the body wall. When the posterior portion of the body wall is fully exposed the needle is inserted approximately one third of the way up the body wall towards the shell attachment muscle. The orientation of the needle should be in line with the plane of the aperture. Penetration of the gonad can be felt by a ‘breaking through’ or sudden decrease in resistance to the progress of the needle. Care should be taken to avoid penetrating further than necessary because other organs can be easily damaged. Drawing the sample requires more force and time (approximately 10 s) than one would expect. When withdrawing the needle constant tension on the syringe plunger is necessary to keep the sample in the needle. The contents of the needle are then emptied on to the glass slide.

scholarly journals An integrated model of brain structure and function

2015 ◽  
Author(s):  
Nick J Beaumont
Keyword(s):  
Action Potentials ◽  
Interstitial Fluid ◽  
Traumatic Injury ◽  
The Body ◽  
Potassium Ions ◽  
Key Characteristics ◽  
Brain Structure And Function ◽  
And Function ◽  
The Brain ◽  
Sodium And Potassium

The fluid in the extracellular space around the neurons and glial cells is enclosed within the brain, kept separate from the circulation and the rest of the body-fluid. This brain interstitial fluid forms a distinct compartment; a sponge-like “inverse cell” that surrounds all the cells. During neuronal resting and action potentials, sodium and potassium ions shuttle into, and out of, this “Reciprocal Domain” within the brain. This localised flux of ions is the counterpart to all the neuronal electrochemical activity (having the same intensity and duration, at the same sites in the brain), so a complementary version of all that potential information is integrated into this space within the brain. This flux of cations in the Reciprocal Domain may indirectly influence neuronal activity in the brain, creating immensely complex feedback. This Reciprocal Domain is unified throughout the brain, and exists continuously throughout life. This model identifies which species have such Reciprocal Domains, and how many times similar systems evolved. This account of the Reciprocal Domain of the brain may have clinical implications; it could be vulnerable to disruption by chemical insult, traumatic injury or pathology. These are key characteristics of our core selves; this encourages the idea that this Reciprocal Domain makes a crucial contribution to the brain. This hypothesis is explored and developed here.

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