scholarly journals Swimming in the Pteropod Mollusc, Clione Limacina: II. Physiology

1985 ◽  
Vol 116 (1) ◽  
pp. 205-222 ◽  
Author(s):  
RICHARD A. SATTERLIE ◽  
ANDREW N. SPENCER
Keyword(s):  
Electrical Coupling ◽  
Pattern Generator ◽  
Pattern Generation ◽  
Motor Neurone ◽  
Pedal Ganglion ◽  
Complex Activity ◽  
Firing Patterns ◽  
Friday Harbor ◽  
Tightly Coupled ◽  
Motor Neurones

The central pattern generator (CPG) for swimming inClione limacina was localized in cutting experiments. A separate pattern generator for each wing islocated in the ipsilateral pedal ganglion. The CPGs are tightly coupled butcan be isolated by severing the pedal commissure. Removal of the cerebralganglia results in a decrease in swim frequency and regularity suggesting descending modulation of the CPGs. Two classes of pedal neurones display firing patterns in phase with swimming movements. One class, swim motor neurones, are further divided intodepressor and elevator groups. Motor neurone recordings show complex subthreshold activity consisting of alternate depolarizations and hyperpolarizations. The complex activity is in antiphase in antagonistic motorneurones. Significant motor neurone-motor neurone interactions do notoccur centrally as neither electrical coupling nor chemical synaptic interactionscould be demonstrated. Injected currents do not alter the motorneurone firing rhythm or the swimming rhythm. Motor neurone cell bodies are located in the lateral region of the ipsilateralpedal ganglion, near the emergence of the wing nerve. Each motor neuroneprovides a single axon to the wing nerve which branches repeatedly in thewing. Each motor neurone has an extremely large innervation field, somecovering up to half of the wing area. The second class of pedal neurones that display firing patterns in phasewith either wing upswing or downswing are pedal-pedal inter neurones. Eachswim interneurone provides axon branches in both pedal ganglia and the axonruns in the pedal commissure. Interneurone axon branches occur in thelateral neuropile of each pedal ganglion, in the region of motor neurone branching.The swim interneurones presumably play a major role in bilateralcoordination of the wings and are involved in pattern generation since injectedcurrents were found to accelerate or slow the firing rhythms of interneuronesand motor neurones, and wing movements. Note: A significant portion of this work was conducted at Friday Harbor Laboratories, Friday Harbor, Washington, U.S.A.

scholarly journals Functional Principles of Pattern Generation for Walking Movements of Stick Insect Forelegs: The Role of the Femoral Chordotonal Organ Afferences

1988 ◽  
Vol 136 (1) ◽  
pp. 125-147 ◽  
Author(s):  
ULRICH BÄSSLER
Keyword(s):  
Pattern Generator ◽  
Stick Insect ◽  
Pattern Generation ◽  
Chordotonal Organ ◽  
Step Cycle ◽  
Strongly Coupled ◽  
Loosely Coupled ◽  
Active Reaction ◽  
Motor Neurones ◽  
High Stimulus

A rampwise stretch of the femoral chordotonal organ is known often to elicit a response in the active decerebrate stick insect that is termed an ‘active reaction’, and which can be considered to represent part of the step cycle. During the first part of the response, the flexor motor neurones are excited and the excitatory extensor motor neurones are inhibited, forming a positive feedback loop. When the chordotonal organ reaches a position corresponding to a flexed femur-tibia joint, the flexor motor neurones are inhibited and the extensor motor neurones are excited. In this study, extracellular and intracellular recordings showed that, during an active reaction, the excitation of the retractor unguis motor neurones usually paralleled that of the flexor motor neurones, whereas the protractor coxae motor neurones were less strongly coupled to this system. The first part of the active reaction occurred only at low stimulus velocities. At high stimulus velocities negative feedback was present. The first part therefore represents some kind of velocity-control-system for active flexions. Electrical stimulation of the nerve containing the axons of trochanteral campaniform sensilla and of the hairfield trHP decreased the likelihood that concurrent chordotonal organ stimulation would elicit an active reaction. Furthermore, most of the active reactions that occurred under these stimulus conditions involved only the flexor tibiae muscle. The results indicate that: the walking pattern generator is composed of subunits that are only loosely coupled centrally; it probably does not include a central pattern generator; and generation of an active reaction is a two-step process.

Two interconnected kernels of reciprocally inhibitory interneurons underlie alternating left-right swim motor pattern generation in the mollusk Melibe leonina

2014 ◽  
Vol 112 (6) ◽  
pp. 1317-1328 ◽  
Author(s):  
Akira Sakurai ◽  
Charuni A. Gunaratne ◽  
Paul S. Katz
Keyword(s):  
Motor Pattern ◽  
Pattern Generator ◽  
Swimming Behavior ◽  
Pattern Generation ◽  
Inhibitory Neurons ◽  
Inhibitory Interneurons ◽  
Pedal Ganglion ◽  
Rhythmic Motor ◽  
Fixed Phase ◽  
Motor Pattern Generation

The central pattern generator (CPG) underlying the rhythmic swimming behavior of the nudibranch Melibe leonina (Mollusca, Gastropoda, Heterobranchia) has been described as a simple half-center oscillator consisting of two reciprocally inhibitory pairs of interneurons called swim interneuron 1 (Si1) and swim interneuron 2 (Si2). In this study, we identified two additional pairs of interneurons that are part of the swim CPG: swim interneuron 3 (Si3) and swim interneuron 4 (Si4). The somata of Si3 and Si4 were both located in the pedal ganglion, near that of Si2, and both had axons that projected through the pedal commissure to the contralateral pedal ganglion. These neurons fulfilled the criteria for inclusion as members of the swim CPG: 1) they fired at a fixed phase in relation to Si1 and Si2, 2) brief changes in their activity reset the motor pattern, 3) prolonged changes in their activity altered the periodicity of the motor pattern, 4) they had monosynaptic connections with each other and with Si1 and Si2, and 5) their synaptic actions helped explain the phasing of the motor pattern. The results of this study show that the motor pattern has more complex internal dynamics than a simple left/right alternation of firing; the CPG circuit appears to be composed of two kernels of reciprocally inhibitory neurons, one consisting of Si1, Si2, and the contralateral Si4 and the other consisting of Si3. These two kernels interact with each other to produce a stable rhythmic motor pattern.

Central connections of sensory neurones from a hair plate proprioceptor in the thoraco-coxal joint of the locust.

1995 ◽  
Vol 198 (7) ◽  
pp. 1589-1601 ◽  
Author(s):  
F Kuenzi ◽  
M Burrows
Keyword(s):  
Stance Phase ◽  
Swing Phase ◽  
Motor Neurone ◽  
Sensory Neurone ◽  
Sensory Neurones ◽  
Selective Stimulation ◽  
Basal Joint ◽  
Motor Neurones ◽  
Individual Motor ◽  
Stimulation Of

The hair plate proprioceptors at the thoraco-coxal joint of insect limbs provide information about the movements of the most basal joint of the legs. The ventral coxal hair plate of a middle leg consists of group of 10-15 long hairs (70 microns) and 20-30 short hairs (30 microns). The long hairs are deflected by the trochantin as the leg is swung forward during the swing phase of walking, and their sensory neurones respond phasically during an imposed deflection and tonically if the deflection is maintained. Selective stimulation of the long hairs elicits a resistance reflex that rotates the coxa posteriorly and is similar to that occurring at the transition from the swing to the stance phase of walking. The motor neurones innervating the posterior rotator and adductor coxae muscles are excited, and those to the antagonistic anterior rotator muscle are inhibited. By contrast, selective stimulation of the short hairs leads only to a weak inhibition of the anterior rotator. The excitatory effects of the long hairs are mediated, in part, by direct connections between their sensory neurones and particular motor neurones. A spike in a sensory neurone elicits a short-latency depolarising postsynaptic potential (PSP) in posterior rotator and adductor motor neurones whose amplitude is enhanced by hyperpolarising current injected into the motor neurone. When the calcium in the saline is replaced with magnesium, the amplitude of the PSP is reduced gradually, and not abruptly as would be expected if an interneurone were interposed in the pathway. Several sensory neurones from long hairs converge to excite an individual motor neurone, evoking spikes in some motor neurones. The projections of the sensory neurones overlap with some of the branches of the motor neurones in the lateral association centre of the neuropile. It is suggested that these pathways would limit the extent of the swing phase of walking and contribute to the switch to the stance phase in a negative feedback loop that relieves the excitation of the hairs by rotating the coxa backwards.

The Physiology and Morphology of Median Nerve Motor Neurones in the Thoracic Ganglia of the Locust

1982 ◽  
Vol 96 (1) ◽  
pp. 325-341
Author(s):  
MALCOLM BURROWS
Keyword(s):  
Synaptic Input ◽  
Motor Neurone ◽  
Abdominal Muscles ◽  
Thoracic Ganglia ◽  
Synaptic Potentials ◽  
Metathoracic Ganglion ◽  
Inspiratory Motor ◽  
Motor Neurones ◽  
Chemical Synapses ◽  
The Right

Simultaneous intracellular recordings have been made from the two expiratory, and from the two inspiratory motor neurones which have their axons in the unpaired median nerves of the thoracic ganglia. Each motor neurone has an axon that branches to innervate muscles on the left and on the right side of one segment. The expiratory neurones studied were those in the meso- and meta-thoracic ganglia which innervate spiracular closer muscles. The depolarizing synaptic potentials underlying the spikes during expiration are common to the two closer motor neurones in a particular segment. Similarly, during inspiration when there are usually no spikes, the hyperpolarizing, inhibitory potentials are also common to both motor neurones. The synaptic input to the neurones can be derived from four interneurones; two responsible for the depolarizing potentials during expiration and two for the inhibitory potentials during inspiration. The inspiratory neurones studied were those in the abdominal ganglia fused to the metathoracic ganglion which innervate dorso-ventral abdominal muscles. During inspiration the two motor neurones of one segment spike at a similar and steady frequency. The underlying synaptic input to the two is common. During expiration, when there are usually no spikes, the hyperpolarizing synaptic potentials are also common to both neurones. In addition they match exactly the depolarizing potentials occurring at the same time in the closer motor neurones. The same set of interneurones could be responsible. No evidence has been revealed to indicate that the two closer, or the two inspiratory motor neurones of one segment are directly coupled by electrical or chemical synapses. The morphology of both types of motor neurone is distinct from that of other motor neurones in these ganglia. Both types branch extensively in both the left and in the right areas of the neuropile.

Peripheral control of the gain of a central synaptic connection between antagonistic motor neurones in the locust

1996 ◽  
Vol 199 (3) ◽  
pp. 613-625
Author(s):  
T Jellema ◽  
W Heitler
Keyword(s):  
Muscle Contraction ◽  
Sensory Input ◽  
Sense Organ ◽  
Gain Control ◽  
Motor Neurone ◽  
Extensor Muscle ◽  
Chordotonal Organ ◽  
Excitatory Postsynaptic Potential ◽  
Motor Neurones ◽  
Peripheral Sensory

The metathoracic fast extensor tibiae (FETi) motor neurone of locusts is unusual amongst insect motor neurones because it makes output connections within the central nervous system as well as in the periphery. It makes excitatory chemical synaptic connections to most if not all of the antagonist flexor tibiae motor neurones. The gain of the FETi-flexor connection is dependent on the peripheral conditions at the time of the FETi spike. This dependency has two aspects. First, sensory input resulting from the extensor muscle contraction can sum with the central excitatory postsynaptic potential (EPSP) to augment its falling phase if the tibia is restrained in the flexed position (initiating a tension-dependent reflex) or is free to extend (initiating a movement-dependent resistance reflex). This effect is thus due to simple postsynaptic summation of the central EPSP with peripheral sensory input. Second, the static tibial position at the time of the FETi spike can change the amplitude of the central EPSP, in the absence of any extensor muscle contraction. The EPSP can be up to 30 % greater in amplitude if FETi spikes with the tibia held flexed rather than extended. The primary sense organ mediating this effect is the femoral chordotonal organ. Evidence is presented suggesting that the mechanism underlying this change in gain may be specifically localised to the FETi-flexor connection, rather than being due to general position-dependent sensory feedback summing with the EPSP. The change in the amplitude of the central EPSP is probably not caused by general postsynaptic summation with tonic sensory input, since a diminution in the amplitude of the central EPSP caused by tibial extension is often accompanied by overall tonic excitation of the flexor motor neurone. Small but significant changes in the peak amplitude of the FETi spike have a positive correlation with changes in the EPSP amplitude, suggesting a likely presynaptic component to the mechanism of gain control. The change in amplitude of the EPSP can alter its effectiveness in producing flexor motor output and, thus, has functional significance. The change serves to augment the effectiveness of the FETi-flexor connection when the tibia is fully flexed, and thus to increase its adaptive advantage during the co-contraction preceding a jump or kick, and to reduce the effectiveness of the connection when the tibia is partially or fully extended, and thus to reduce its potentially maladaptive consequences during voluntary extension movements such as thrusting.

INTEGRATION OF POSITIVE AND NEGATIVE FEEDBACK LOOPS IN A CRAYFISH MUSCLE

1994 ◽  
Vol 187 (1) ◽  
pp. 305-313
Author(s):  
P Skorupski ◽  
P Vescovi ◽  
B Bush
Keyword(s):  
Negative Feedback ◽  
Positive Feedback ◽  
Motor Neurone ◽  
Chordotonal Organ ◽  
Negative Feedback Loops ◽  
Reflex Pathways ◽  
Motor Neurones ◽  
Receptor Organ ◽  
Group 2

It is now well established that in arthropods movement-related feedback may produce positive, as well as negative, feedback reflexes (Bassler, 1976; DiCaprio and Clarac, 1981; Skorupski and Sillar, 1986; Skorupski et al. 1992; Vedel, 1980; Zill, 1985). Usually the same motor neurones are involved in both negative feedback (resistance) reflex responses and positive feedback reflexes. Reflex reversal involves a shift in the pattern of central inputs to a motor neurone, for example from excitation to inhibition. In the crayfish, central modulation of reflexes has been described in some detail for two basal limb proprioceptors, the thoracocoxal muscle receptor organ (TCMRO) and the thoracocoxal chordotonal organ (TCCO) (Skorupski et al. 1992; Skorupski and Bush, 1992). Leg promotor motor neurones are excited by stretch of the TCMRO (which, in vivo, occurs on leg remotion) in a negative feedback reflex, but when this reflex reverses they are inhibited by the same stimulus. Release of the TCCO (which corresponds to leg promotion) excites some, but not all, promotor motor neurones in a positive feedback reflex. There are at least two ways in which the reflex control of a muscle may be modulated in this system. Firstly, inputs to motor neurones may be routed via alternative reflex pathways to produce different reflex outputs. Secondly, the pattern of inputs to a motor pool may be inhomogeneous, so that activation of different subgroups of the motor pool causes different outputs. Different crayfish promotor motor neurones are involved in different reflexes. On this basis, the motor neurones may be classified into at least two subgroups: those that are excited by the TCCO in a positive feedback reflex (group 1) and those that are not (group 2). Do these motor neurone subgroups have different effects on the promotor muscle, or is the output of the two promotor subgroups summed at the neuromuscular level? To address this question we recorded from the promotor nerve and muscle in a semi-intact preparation of the crayfish, Pacifastacus leniusculus. Adult male and female crayfish, 8-11 cm rostrum to tail, were decapitated and the tail, carapace and viscera removed. The sternal artery was cannulated and perfused with oxygenated crayfish saline, as described previously (Sillar and Skorupski, 1986).

Sensory and Motor Neurones Responsible for the Local Bending Response in Leeches

1982 ◽  
Vol 96 (1) ◽  
pp. 161-180 ◽  
Author(s):  
WILLIAM B. KRISTAN
Keyword(s):  
Body Wall ◽  
Longitudinal Muscle ◽  
Motor Neurone ◽  
Intracellular Recordings ◽  
Firing Rates ◽  
Macrobdella Decora ◽  
Motor Neurones ◽  
The Central Nervous System ◽  
P Cells ◽  
Bending Response

1. Intracellular recordings were made from identified mechanosensory neurones (T and P cells) and longitudinal muscle motor neurones of leeches Hirudo medicinalis and Macrobdella decora while the skin was electrically stimulated to produce local bending responses. 2. The stimulus intensity required to produce local bending was found to activate the mechanosensory neurones at physiological firing rates. For a given stimulation frequency, intracellular activation of the mechanosensory neurones produced the same local bending response as did skin stimulation. Hyperpolarization sufficient to block the propagation of the afferent impulses into the central nervous system eliminated the local bending response to skin stimulation. 3. Stimulating identified longitudinal muscle motor neurones at frequencies observed during the local bending response produced body wall movements similar to those seen in local bending. Hyperpolarization of the motor neurones to block impulse initiation abolished local bending. 4. Mechanosensory neurone to longitudinal muscle motor neurone connexions were demonstrated to be effective and reliable, but polysynaptic for all but the previously documented monosynaptic connexions from mechanosensory neurones onto the L motor neurone (Nicholls & Purves, 1970). 5. It is concluded that the previously identified mechanosensory and motor neurones are exclusively responsible for the local bending response.

The Different Connections and Motor Outputs of Lateral and Medial Giant Fibres in the Crayfish

1971 ◽  
Vol 54 (2) ◽  
pp. 391-404
Author(s):  
JAMES L. LARIMER ◽  
ALAN C. EGGLESTON ◽  
LEONA M. MASUKAWA ◽  
DONALD KENNEDY
Keyword(s):  
High Speed ◽  
Motor Neurone ◽  
Giant Axons ◽  
Procion Yellow ◽  
High Speed Cinematography ◽  
Motor Neurones ◽  
Motor Outputs ◽  
Giant Fibres ◽  
Tonic System ◽  
Stimulation Of

1. High-speed cinematography was used to analyse the abdominal movements of crayfish in response to separate stimulation of medial and lateral giant axons. These films showed that the medial giant fibres command complete abdominal flexions with little flaring of the tail appendages. The lateral giants, in contrast, evoked a relatively weak flexion of the middle abdominal segments, accompanied by promotion of the exopodites of the uropods. 2. An examination of the muscles activated by the two types of giant fibres shows that differences in the connexions between the giant fibres and specific motor neurones can account for the behavioural differences observed. 3. The output of the giant fibres was determined in the sixth abdominal ganglion, where their differential effects are most pronounced. The medial giants activate motor neurones whose axons emerge from root 6 of the sixth ganglion. The lateral giants activate motor neurones whose axons emerge via roots 2 and 3, as well as those emerging via root 6. 4. The larger motor neurones associated with the giant axons in the sixth root of the sixth ganglion have been mapped by Procion Yellow injection, and the terminations of the central giant axons in the sixth ganglion have also been determined. The connexions revealed by this technique are consistent with the physiological findings. 5. The evidence suggests that root 6 of the sixth ganglion is homologous with root 3 of the more anterior ganglia. However, the giant motor neurone of the sixth ganglion has not been identified. 6. The medial and lateral giant fibres, and perhaps other specific ‘command’ interneurones, can thus drive specific ensembles of phasic motor neurones to provide a range of stereotyped quick movements. In this respect the organization of the phasic system of interneurones and motor neurones resembles that in the tonic system.

An Arthropod Muscle Innervated by Nine Excitatory Motor Neurones

1980 ◽  
Vol 88 (1) ◽  
pp. 249-258
Author(s):  
CHRISTINE E. PHILLIPS
Keyword(s):  
Action Potentials ◽  
Motor Neurone ◽  
Muscle Fibres ◽  
Relaxation Rates ◽  
Motor Neurones ◽  
The Individual ◽  
Contraction And Relaxation ◽  
High Degree ◽  
Individual Motor ◽  
Indirect Stimulation

The anatomical and physiological organization of the locust metathoracic flexor tibiae was examined by a combination of intracellular recording and electron microscopy. Nine excitatory motor neurones, three fast, three intermediate and three slow innervate the muscle; each is uniquely identifiable using a combination of physiological response and soma location. A simple spatial distribution of inputs to the muscle from the individual motor neurones was not found. Individual muscle fibres responded to as many as seven of the motor neurones in various combinations. The muscle fibres are heterogeneous, ranging from slow (tonic) to fast (phasic) in a continuum from predominantly phasic proximally to tonicdistally. This is demonstrated by contraction and relaxation rates to directand indirect stimulation, as well as contraction elicited by action potentials in a single flexor motor neurone. The fast and slow contractile properties of the muscle fibres are matched by appropriate ultrastructures. Such a high degree of complexity of neuromuscular innervation as that found in the metathoracic flexor tibiae has not previously been described for an arthropod muscle.

Comparison of slow larval and fast adult muscle innervated by the same motor neurone

1980 ◽  
Vol 84 (1) ◽  
pp. 103-118
Author(s):  
M. B. Rheuben ◽  
A. E. Kammer
Keyword(s):  
Developmental Stages ◽  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Thick Filament ◽  
Motor Neurone ◽  
Muscle Fibre Types ◽  
Thin Filaments ◽  
Adult Muscle ◽  
Motor Neurones ◽  
Two Stages

1. Muscles innervated by an identified set of motor neurones were compared between larval and adult stages. 2. The structure of the larval muscle is typically tonic: long sarcomeres, irregular Z-bands, and 10-12 thin filaments around each thick filament. The structure of the adult muscle is phasic: 3-4 micrometers sarcomeres, regular Z-bands, 6-8 thin filaments around each thick filament, and large mitochondrial volume. 3. The tensions produced by these muscles were correspondingly different. The larval twitch was about 7 times slower and the tetanus/twitch ratio 10 times greater than those of the adult. 4. No structural or physiological differences were observed in the neuromuscular junctions of the two stages. 5. The relatively unchanging functional relationship of a single motor neurone with two different muscle fibre types during two developmental stages is compared with the converse situation in which it has been reported that implantation of a different type of motor nerve into a muscle modifies contractile properties.

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