Physiology of Water Motion Detection in the Medicinal Leech

1981 ◽  
Vol 92 (1) ◽  
pp. 255-275
Author(s):  
W. OTTO FRIESEN
Keyword(s):  
Neuronal Activity ◽  
Water Waves ◽  
Nerve Cord ◽  
Action Potentials ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
Medicinal Leech ◽  
Afferent Input ◽  
Excitatory Input ◽  
Simultaneous Action

1. Neuronal activity resulting from stimulation by water waves occurs in ventral nerve cord-body wall preparations of the medicinal leech, Hirudo medicinalis. In segmental nerves, this activity consists of afferent compound action potentials with graded amplitudes resulting from simultaneous action potentials in many small sensory axons. Afferent input impinging on one segmental ganglion activates neuronal activity along much of the ventral nerve cord. 2. Previously identified tactile mechanoreceptors are insensitive to low-amplitude wave stimulation. Touch-cell impulse activity can be evoked by moderate or strong wave stimulation, but these impulses appear to arise near the cell body, not from the peripheral receptor endings. 3. The transduction sites for wave stimulation are localized at or very near the segmental sensilla. Because of their location and modality the receptors were named ‘sensillar movement receptors’ (SMR). 4. S cells (Rohde's fibre) receive suprathreshold excitatory input during SMR activation without concomitant activity in the tactile mechanoreceptors. 5. The annulus erector motor neurones contralateral to the afferent SMR inflow are inhibited by SMR activation. This inhibition is also observed in ganglia adjacent to the ganglion receiving the afferent input and provides a neuronal basis for reflexive smoothing of the leech body wall. 6. Two neurones in the anterior median packet of segmental ganglia receive powerful synaptic input during SMR activation. One, cell 202, receives 10 mV excitatory potentials while the other, cell 201, receives 10 mV inhibitory potentials.

scholarly journals Habituation of swimming activity in the medicinal leech

1985 ◽  
Vol 116 (1) ◽  
pp. 169-188
Author(s):  
E. A. Debski ◽  
W. O. Friesen
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
Spontaneous Recovery ◽  
Medicinal Leech ◽  
The Body ◽  
Swimming Activity ◽  
Stimulus Generalization ◽  
Anterior Segments ◽  
Stimulation Of

Tactile stimulation (light stroking) of a body wall flap attached to the ventral nerve cord of the medicinal leech evokes episodes of swimming activity. This swimming response undergoes habituation, involving changes in swim initiation and swim maintenance. Repeated stimulation of the body wall flap evoked swimming activity between three and 39 times before this response failed. During repetitive stimulation, the length of swim episodes decreased by about 50%. The number of swim episodes which could be elicited was not correlated with swim episode length. Following habituation, swim initiation showed significant spontaneous recovery, but swim episode length returned only to 60% of control values. In preparations where spontaneous recovery was followed by rehabituation, the number of swim episodes elicited declined with each habituation-recovery sequence. Additional stimulation immediately following habituation trials had a dual effect: recovery of the swimming response was delayed, but the lengths of swim episodes following spontaneous recovery were increased. Pinching the body wall flap immediately restored the swimming response in an habituated preparation. Swim initiation habituated more rapidly during stimulation of anterior body wall flaps than during stimulation of mid-body or posterior flaps. However, swim length was independent of this regional variation in swim responsiveness. The number of swim episodes elicited by stimulation of body wall flaps attached to posterior or anterior segments depended upon whether this segment was stimulated before or after other flaps. In contrast, in mid-body segments there was no evidence for such stimulus generalization. The lengths of swim episodes elicited during sequential stimulation of several body wall flaps were independent of the stimulation sequence. We propose that separate processes control swim initiation and swim maintenance. These processes must be repeated in most, if not all, of the segmental ganglia of the leech ventral nerve cord.

scholarly journals Mutations Affecting Nerve Attachment of Caenorhabditis elegans

Genetics ◽  
2001 ◽  
Vol 157 (4) ◽  
pp. 1611-1622 ◽  
Author(s):  
Go Shioi ◽  
Michinari Shoji ◽  
Masashi Nakamura ◽  
Takeshi Ishihara ◽  
Isao Katsura ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
The Body ◽  
Genetic Loci ◽  
Muscle Attachment ◽  
C Elegans ◽  
Ventral Cord ◽  
Excretory Canal

Abstract Using a pan-neuronal GFP marker, a morphological screen was performed to detect Caenorhabditis elegans larval lethal mutants with severely disorganized major nerve cords. We recovered and characterized 21 mutants that displayed displacement or detachment of the ventral nerve cord from the body wall (Ven: ventral cord abnormal). Six mutations defined three novel genetic loci: ven-1, ven-2, and ven-3. Fifteen mutations proved to be alleles of previously identified muscle attachment/positioning genes, mup-4, mua-1, mua-5, and mua-6. All the mutants also displayed muscle attachment/positioning defects characteristic of mua/mup mutants. The pan-neuronal GFP marker also revealed that mutants of other mua/mup loci, such as mup-1, mup-2, and mua-2, exhibited the Ven defect. The hypodermis, the excretory canal, and the gonad were morphologically abnormal in some of the mutants. The pleiotropic nature of the defects indicates that ven and mua/mup genes are required generally for the maintenance of attachment of tissues to the body wall in C. elegans.

scholarly journals MUSCLE TENSION AND REFLEXES IN THE EARTHWORM

1923 ◽  
Vol 5 (3) ◽  
pp. 327-333 ◽  
Author(s):  
A. R. Moore
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
Muscle Tension ◽  
Posterior Part ◽  
The Body ◽  
Entire Length ◽  
Sensory Cells ◽  
Ventral Region ◽  
Anterior Segments

1. By the use of preparations of earthworm in which the cutaneous receptors have been anesthetized with a solution of M/8 MgCl2, it is shown that peristalsis can be initiated by tension alone. 2. The receptors of the tension reflex are the intermyal sensory cells of the ventral region of the body wall. 3. It is concluded that Straub obtained the tension reflex because his preparations contained the intermyal receptors; Budington was unable to observe the tension reflex in any preparation from which the intermyal receptors had been removed. 4. Intermyal receptors are the receptors of the following reaction: Passive unilateral tension of the posterior part of an earthworm induces active homolateral tension of the musculature of the anterior segments, and results in the course of progress being brought into line with the enforced orientation of the tail. This reaction is termed the homostrophic reflex. 5. The receptors for the reaction are distributed throughout the entire length of the worm, the effectors are limited to the anterior 15 to 20 segments. The impulse is conducted by the ventral nerve cord. 6. The interaction of the homostrophic reflex and tropisms is considered.

scholarly journals Synaptic transmission of nervous impulses through the last abdominal ganglion of the cockroach

1937 ◽  
Vol 122 (826) ◽  
pp. 106-118 ◽  
Keyword(s):  
Synaptic Transmission ◽  
Nerve Cord ◽  
Action Potentials ◽  
Ventral Nerve Cord ◽  
Abdominal Ganglion ◽  
Acoustic Stimuli ◽  
Excellent Opportunity ◽  
Random Activity ◽  
Previous Communication

In a previous communication (1936) we have described the response of the cereal nerve of the cricket when the cercus is subjected to acoustic stimuli. In the course of that work we attempted to trace the afferent fibres to their destination by recording from the ventral nerve cord at various levels anterior to the last abdominal ganglion. It was immediately apparent that, while some of the fibres from the acoustically sensitive end-organs of the cercus ran directly through the ganglion and up the cord, others terminated in the ganglion in synaptic relation with a relatively small number of fibres running forwards in the cord and yielding action potentials of considerable magnitude. Contrary to expectation we found that, subject to certain conditions noted below, the random activity in the abdominal nerve cord was never large enough to obscure the wanted signals, and it seemed to us that the preparation offered an excellent opportunity for an examination of the properties of a central nervous synapse. This paper describes the results of this examination.

scholarly journals Neuronal control of swimming in the medicinal leech. V. Connexions between the oscillatory interneurones and the motor neurones

1978 ◽  
Vol 75 (1) ◽  
pp. 45-63
Author(s):  
M. Poon ◽  
W. O. Friesen ◽  
G. S. Stent
Keyword(s):  
Activity Pattern ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Medicinal Leech ◽  
Exceptional Case ◽  
Motor Neurone ◽  
Phasic Activity ◽  
Neuronal Control ◽  
Motor Neurones ◽  
Pattern Characteristic

A network of intra- and intersegmental synaptic connexions has been identified in the ventral nerve cord of the leech that links the set of oscillatory interneurones of the central swim oscillator to the motor neurones commanding the swimming rhythm. Excitatory connexions lead from oscillatory interneurones to both excitatory and inhibitory motor neurones, whereas inhibitory connexions lead from oscillatory interneurones to only the inhibitory motor neurones. Connexions leading from a motor neurone back to the oscillatory interneurones were found in only one exceptional case, an inhibitory motor neurone previously known to have access to the central swim oscillator. This network of identified connexions can account reasonably well for the mechanism by which the oscillatory interneurones drive their follower motor neurones into the phasic activity pattern characteristic of the swimming movement.

scholarly journals Unpaired Median Neurones in a Lepidopteran Larva (Antheraea Pernyi): I. Anatomy and Physiology

1988 ◽  
Vol 136 (1) ◽  
pp. 311-332 ◽  
Author(s):  
S. J. BROOKES ◽  
R. G. DE WEEVERS
Keyword(s):  
Nerve Cord ◽  
Action Potentials ◽  
Ventral Nerve Cord ◽  
Intracellular Recordings ◽  
Suboesophageal Ganglion ◽  
Antheraea Pernyi ◽  
Anatomy And Physiology ◽  
Branching Patterns ◽  
The Common ◽  
Synaptic Drive

The anatomy and physiology of two unpaired median neurones (MC1 and MC2) with bilaterally symmetrical axons in abdominal ganglia 3, 4, 5 and 6 of Antheraea pernyi larvae were studied. Intracellular dye filling of MC1 and MC2 revealed that they were distinguishable from all other neurones in the ganglia and that they both had axons projecting out of the ganglia in right and left nerves 1. The two cells were identical in their central anatomy and physiology, but could be distinguished from one another by their peripheral branching patterns. The significance of these patterns was investigated by detailed study of the neural and muscular anatomy of the proleg-bearing segments 3, 4, 5 and 6. The peripheral axons of MC1 and MC2 were exclusively associated with nerve trunks that could be traced to blocks of muscle. Intracellular recordings of the two median cells characteristically showed overshooting soma action potentials that were followed by a long afterhyperpolarization lasting many seconds. Simultaneous recordings from median cells in the same ganglion revealed that MC1 and MC2 shared an excitatory synaptic drive that largely determined their patterns of firing. Recordings from median cells in different ganglia showed that the common synaptic drive was also shared by median cells in different segments. Selective lesions of the ventral nerve cord indicated that the synaptic drive to MC1 and MC2 originated in the suboesophageal ganglion. These cells were similar in anatomy and physiology to the median cells in several other insects.

Neuronal control of swimming in the medicinal leech. IV. Identification of a network of oscillatory interneurones

1978 ◽  
Vol 75 (1) ◽  
pp. 25-43
Author(s):  
W. O. Friesen ◽  
M. Poon ◽  
G. S. Stent
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wave ◽  
Medicinal Leech ◽  
The Body ◽  
Cycle Period ◽  
Neuronal Control ◽  
Swimming Movement ◽  
Analogue Models ◽  
Motor Neurones

Four oscillatory interneurones that appear to be the principal components of the central swim oscillator of Hirudo medicinalis have been identified on each side of the segmental ganglia of the ventral nerve cord. During ‘swimming’ episodes of an isolated nerve cord preparation each interneurone undergoes a polarization rhythm that is phase-locked with the impulse burst rhythm of the motor neurones known to drive the swimming movement. Passage of current into any of the interneurones can shift the phase of the swim rhythm. One of the interneurones projects its axon rearward to posterior ganglia and the other three project their axons frontward to anterior ganglia. The oscillatory interneurones are connected both intra- and interganglionically to form a topologically complex intersegmental network of concatenated ring circuits that possess the feature of recurrent cyclic inhibition. Theoretical analysis and electronic analogue models show that the network is inherently oscillatory and can produce both a cycle period and intra- and intersegmental phase relations of its elements that are appropriate for generating the body wave of the swimming movement.

Extracellular filaments in the perineurium of the florida lobster, Panulirus argus

1987 ◽  
Vol 45 ◽  
pp. 784-785
Author(s):  
Roy J. Baerwald ◽  
Lura C. Williamson
Keyword(s):  
Blood Brain Barrier ◽  
Glial Cells ◽  
Tannic Acid ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Florida Keys ◽  
Panulirus Argus ◽  
Brain Barrier ◽  
Cacodylate Buffer ◽  
Nerve Cords

In arthropods the perineurium surrounds the neuropile, consists of modified glial cells, and is the morphological basis for the blood-brain barrier. The perineurium is surrounded by an acellular neural lamella, sometimes containing scattered collagen-like fibrils. This perineurial-neural lamellar complex is thought to occur ubiquitously throughout the arthropods. This report describes a SEM and TEM study of the sheath surrounding the ventral nerve cord of Panulirus argus.Juvenile P. argus were collected from the Florida Keys and maintained in marine aquaria. Nerve cords were fixed for TEM in Karnovsky's fixative and saturated tannic acid in 0.1 M Na-cacodylate buffer, pH = 7.4; post-fixed in 1.0% OsO4 in the same buffer; dehydrated through a graded series of ethanols; embedded in Epon-Araldite; and examined in a Philips 200 TEM. Nerve cords were fixed for SEM in a similar manner except that tannic acid was not used.

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