The Motor Innervation and Musculature of the Antennule of the Hermit Crab, Pagurus Alaskensis (Benedict)

1973 ◽  
Vol 58 (3) ◽  
pp. 767-784
Author(s):  
P. J. SNOW
Keyword(s):  
Hermit Crab ◽  
Muscle Tension ◽  
Low Frequency ◽  
Muscle Fibres ◽  
Intracellular Recordings ◽  
Motor Innervation ◽  
Postsynaptic Inhibition ◽  
Tonic Component ◽  
Whole Muscle ◽  
Tonic Tension

1. The motor innervation and musculature of the medial and distal segments of the hermit-crab antennule have been described anatomically. 2. Intracellular recordings within these muscles and simultaneous monitoring of whole-muscle tension have been used to define the motoneurones and contractile properties of the muscle fibres they innervate. 3. The motor system consists of two fast, two slow and one mixed muscle which are innervated by seven motoneurones. 4. The motor innervation is such that this system may be divided into three components: phasic, phasic-tonic and tonic. The possible involvement of these components in the antennular activities is discussed. 5. The tonic component is adapted to produce fine tonic tension in response to relatively low-frequency (5-10/sec) motoneurone discharge. It is suggested that this may be important for the postural control of appendages which, owing to the density of the environmental medium, are relatively weightless. 6. No evidence of postsynaptic inhibition was found, and this is discussed in relation to the movements of the antennule.

Innervation pattern of a pool of nine excitatory motor neurons in the flexor tibiae muscle of a locust hind leg

1998 ◽  
Vol 201 (12) ◽  
pp. 1885-1893 ◽  
Author(s):  
K Sasaki ◽  
M Burrows
Keyword(s):  
Motor Neurons ◽  
Muscle Fibres ◽  
Main Body ◽  
Intracellular Recordings ◽  
Innervation Pattern ◽  
Flexor Muscle ◽  
Fibre Bundles ◽  
Metathoracic Ganglion ◽  
Overlapping Sets ◽  
Individual Motor

The flexor tibiae muscle of a locust hind leg consists of 10-11 pairs of fibre bundles in the main body of the muscle and a distal pair of bundles that form the accessory flexor muscle, all of which insert onto a common tendon. It is much smaller than the antagonistic extensor tibiae muscle and yet it is innervated by nine excitatory motor neurons, compared with only two for the extensor. To determine the pattern of innervation within the muscle by individual motor neurons, branches of the nerve (N5B2) that supplies the different muscle bundles were backfilled to reveal somata in the metathoracic ganglion. This showed that different muscle bundles are innervated by different numbers of excitatory motor neurons. Physiological mapping of the innervation was then carried out by intracellular recordings from the somata of flexor motor neurons in the metathoracic ganglion using microelectrodes. Spikes were evoked in these neurons by the injection of current, and matching junctional potentials were sought in fibres throughout the muscle using a second intracellular electrode. Each motor neuron innervates only a restricted array of muscle fibres and, although some innervate a larger array than others, none innervates fibres throughout the muscle. Some motor neurons innervate only proximal fibres and others only more distal fibres, so that the most proximal and most distal bundles of muscle fibres are innervated by non-overlapping sets of motor neurons. More motor neurons innervate proximal bundles than distal ones, and there are some asymmetries in the number of motor neurons innervating corresponding bundles on either side of the tendon. Individual motor neurons cause slow, fast or intermediate movements of the tibia, but their patterns of innervation overlap in the different muscle bundles. Furthermore, individual muscle fibres may also be innervated by motor neurons with different properties.

The Action of the Eyecup Muscles of the Crab, Carcinus, During Optokinetic Movements

1968 ◽  
Vol 49 (2) ◽  
pp. 223-250
Author(s):  
M. BURROWS ◽  
G. A. HORRIDGE
Keyword(s):  
Large Amplitude ◽  
Optokinetic Nystagmus ◽  
Wide Spectrum ◽  
Muscle Tension ◽  
The Other ◽  
Fibre Types ◽  
Muscle Fibres ◽  
Exact Form ◽  
Slow Movement ◽  
The One

1. The actions of the nine eyecup muscles of the crab during horizontal optokinetic movements are described. 2. Each muscle includes a wide spectrum of fibre types, ranging from phasic, with sarcomere lengths of 3-4 µm., through intermediate, to tonic fibres with sarcomeres of 10-12 µm. Each muscle receives at least one slow and one fast motoneuron, but no inhibitory supply. The slow axons predominantly innervate the tonic muscle fibres while the fast axons innervate the phasic ones. 3. Slow movement and the position of the eyecup in space are controlled by the frequency of slow motoneuron discharges. All muscles collaborate at every position. The phasic system is recruited during rapid eyecup movements of large amplitude. 4. In optokinetic nystagmus the exact form of the impulse sequences are described for each muscle. They are the consequence of a visually driven central programme which takes no account of the movement which it generates. Movements in opposite directions involve different central programmes; the one is not merely the reverse of the other. There is no effective proprioceptive feedback from the eyecup joint or from muscle tension receptors.

Innervation of the Anterior and Posterior Levator Muscles of the Fifth Leg of the Crab Carcinus Maenas

1987 ◽  
Vol 127 (1) ◽  
pp. 229-248
Author(s):  
STACIA MOFFETT ◽  
DANIEL P. YOX ◽  
LINDA B. KAHAN ◽  
RICHARD L. RIDGWAY
Keyword(s):  
Muscle Fibre ◽  
Electron Micrographs ◽  
Carcinus Maenas ◽  
Levator Muscle ◽  
Muscle Fibres ◽  
Motor Innervation ◽  
Postsynaptic Potentials ◽  
Common Inhibitor ◽  
The Common ◽  
Nerve Recordings

In the fifth pair of legs, the anterior levator muscle of the basi-ischiopodite (AL) consists of a dorsal thoracic head (ALd), two closely aligned ventral thoracic heads (ALv) and a small coxal head (ALc). Major thoracic subdivisions are separately innervated, whereas the nerve innervating the coxal head projects from ALd. The posterior levator (PL) is located in the coxa and is separately innervated. Nerve recordings, dye backfilling, muscle fibre recordings and nerve crosssections yielded somewhat different estimates for the levator motor innervation. Nerve backfills reveal at least 10 motoneurones supplying AL: six shared by ALd and ALv, one unique to ALv and three unique to ALd. Nerve recordings reveal six motoneurones supplying ALd and five supplying ALv. Four (including the common inhibitor) are shared by ALd and ALv and six project from ALd to ALc. Most AL muscle fibres are innervated by two or three motoneurones, but fibres innervated by five were encountered. Postsynaptic potentials ranging from small (<1-5 mV) to large (15–25 mV) were found distributed throughout AL. PL is innervated by two excitors not shared with AL and by the common inhibitor. Electron micrographs reveal more axons than any of the methods for counting motoneurones. Neurones with axon diameters below 3 μm are likely to be sensory.

Potentiation of Neuromuscular Transmission by an Octopaminergic Neurone in the Locust

1979 ◽  
Vol 79 (1) ◽  
pp. 169-190 ◽  
Author(s):  
MICHAEL O'SHEA ◽  
PETER D. EVANS
Keyword(s):  
Indirect Effects ◽  
Neuromuscular Transmission ◽  
Time Course ◽  
Muscle Tone ◽  
Muscle Tension ◽  
Presynaptic Receptors ◽  
Extensor Muscle ◽  
Muscle Membrane ◽  
Muscle Fibres ◽  
Central Synapses

1. Spikes in the octopaminergic dorsal unpaired median (DUM) neurone which innervates the extensor tibiae muscle of the locust metathoracic leg (DUMETi) produce direct and indirect effects on muscle tension. 2. Direct effects include a slowing of an intrinsic rhythm of contraction and relaxation, a relaxation of muscle tone and a small hyperpolarization of the muscle membrane potential. The latter two effects are weak and variable. All three effects are mimicked by superfusion of octopamine and are mediated by octopamine receptors on the muscle fibres. 3. Indirect effects are found when the DUMETi neurone is stimulated at the same time as the motoneurones innervating the extensor muscle. They include (a) potentiation of tension generated in the extensor muscle by spikes in the slow excitatory motoneurone (SETi), (b) reduction in duration of each twitch contraction generated by SETi due to an increase in the rate at which the muscle relaxes, (c) increase in the amplitude of the synaptic potential generated by SETi. These various effects have a time course of several minutes and far outlast the duration of DUMETi stimulation. They can be mimicked by superfusion of octopamine. 4. The effect of DUMETi on neuromuscular transmission is mediated by receptors with a high affinity for octopamine located both on the muscle and on the terminals of the slow motoneurone. The presence of the presynaptic receptors is revealed by the increase in the frequency of spontaneous miniature end plate potentials recorded in the muscle in the presence of octopamine. 5. DUMETi is a member of a group of similar aminergic neurones and it is suggested that they may share a role in modulating transmission at peripheral neuromuscular synapses, and possibly central synapses.

Role of fascia in maintenance of muscle tension and pressure

1981 ◽  
Vol 51 (2) ◽  
pp. 317-320 ◽  
Author(s):  
S. R. Garfin ◽  
C. M. Tipton ◽  
S. J. Mubarak ◽  
S. L. Woo ◽  
A. R. Hargens ◽  
...  
Keyword(s):  
High Frequency ◽  
Muscle Tension ◽  
Fluid Pressure ◽  
Low Frequency ◽  
Testing Procedure ◽  
Force Transducer ◽  
High Frequency Stimulation ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation

The effect of fasciotomy on muscle tension (measured by a force transducer attached to the tendon) and interstitial fluid pressure (measured by Wick catheters in the muscle belly) was studied in the anterolateral compartments of 13 dog hindlimbs. Muscle tension and pressure were monitored in the tibialis cranialis muscle after low- and high-frequency stimulation of the peroneal nerve to produce twitch- and tetanic-type contractions. Fasciotomy decreased muscle force during the low-frequency stimulation by 16% (35.3 +/- 4.9 to 28.4 +/- 3.9 N) and during the high-frequency stimulation by 10% (60.8 %/- 4.9 to 54.8 +/- 3.9 N). Muscle pressure decreased 50% after fasciotomy under both conditions, 15 +/- 2 to 6 +/- 1 mmHg and 84 +/- 17 to 41 +/- 8 mmHg), respectively. Repeated functional evaluations during the testing procedure indicated that muscle fatigue was not a major factor in these results. It was concluded that fascia is important in the development of muscle tension and changes in interstitial pressure. Furthermore, the results raised questions concerning the merits of performing a fasciotomy for athletes with a compartment syndrome.

Plasticity in mammalian skeletal muscle

1977 ◽  
Vol 278 (961) ◽  
pp. 295-305 ◽  
Keyword(s):  
Skeletal Muscle ◽  
Peripheral Nerve ◽  
Motor Nerve ◽  
Contractile Proteins ◽  
Biochemical Changes ◽  
Muscle Fibres ◽  
Mammalian Skeletal Muscle ◽  
Motor Innervation ◽  
Nerve Impulses ◽  
Contractile Characteristics

While it has been recognized for many years that different limb muscles belonging to the same mammal may have markedly differing contractile characteristics, it is only comparatively recently that it has been demonstrated that these differences depend upon the motor innervation. By appropriately changing the peripheral nerve innervating a mammalian skeletal muscle, it is possible to change dramatically the contractile behaviour of the reinnervated muscle. The manner by which the motor innervation determines the nature of a muscle fibre’s contractile machinery is not completely understood, but it appears that the number and pattern of motor nerve impulses reaching the muscle play an important role. The biochemical changes occurring within muscle fibres whose contractile properties have been modified by altered motor innervation include the synthesis of different contractile proteins.

VIII.—Regeneration of the Legs of Decapod Crustacea from the Preformed Breaking Plane

1915 ◽  
Vol 35 ◽  
pp. 78-94 ◽  
Author(s):  
J. Herbert Paul
Keyword(s):  
Cell Proliferation ◽  
Hermit Crab ◽  
Functional Activity ◽  
Limb Regeneration ◽  
Single Layer ◽  
Shore Crab ◽  
Muscle Fibres ◽  
Rhythmic Movements ◽  
Small Vessels ◽  
Decapod Crustacea

Summary(1) Homarus vulgáris, Eupagurus bernhardus, and Carcinus mœnas all form limb-buds or papillæ in the process of limb regeneration. These are covered by a chitinous envelope, and the observations here recorded show that their outer form and size are adaptations to the requirements of the animal. That of the lobster is straight, that of the hermit crab curved, while the shore crab has a papilla which may be folded on itself three times inside the envelope.(2) Valvular action of the diaphragm at the breaking plane plays a greater part in the stopping of haemorrhage after self-amputation than clotting, and the dilatation of small vessels which pass beneath the epidermis detaches a layer of cells. This layer of epidermis proliferates from its free edges to form the new limb.(3) A new diaphragm is the first structure laid down, and differentiation takes place from the base outwards. Muscle arises at the growing tip from cells proliferated from the old epidermis (an ectodermal structure), and the nerve grows outwards from the torn end by cell proliferation.(4) Muscle-fibres are anatomically complete immediately before moulting. The fibrillæ are cross-striated and enclosed in a sarcolemma, but full functional activity does not come till several days after moulting, beginning with slow rhythmic movements. Sarcoplasm seems to be less plentiful than in the normal fibre.(5) When moulting occurs the papilla is at once expanded to several times its previous size by valvular action, and the epidermis, previously composed of several layers of cells, now thins to a single layer, as is seen in the normal limb.

Reflex control of dynamic muscle stiffness in a slow crustacean muscle

1985 ◽  
Vol 54 (2) ◽  
pp. 403-417 ◽  
Author(s):  
W. D. Chapple
Keyword(s):  
Muscle Tension ◽  
Fold Increase ◽  
Muscle Stiffness ◽  
Peak Force ◽  
Substantial Part ◽  
Burst Frequency ◽  
Pass Filter ◽  
Tonic Component ◽  
Low Pass Filter ◽  
Fourth Segment

The properties of a stretch reflex in the ventral superficial muscle of the hermit crab abdomen were studied in an isolated abdominal preparation to determine how the reflex affects the mechanical properties of the muscle and whether the reflex is controlling length, force, or stiffness. The reflex was elicited by stretch of hypodermal mechanoreceptors in the cuticle and resulted in the activation of excitor motoneurons to both circular and longitudinal layers of the muscle, thus stiffening the abdomen. The medial motoneuron of the longitudinal layer of the right fourth segment was selected for detailed analysis. It was tonically active and responded to stretch with a phasic burst having a latency of 100 ms. Reflex muscle tension began to increase at 130 ms and reached a peak at 300 ms. Reflex-burst frequency increased slightly with stretch amplitude. Peak force was an approximately linear function of stretch amplitude. No tonic component to the reflex was found in the medial motoneuron, in the central motoneuron (the smallest excitor to the muscle), or in the medial motoneuron studied in intact animals. The reflex-burst frequency was a function of stretch velocity, increasing between two and one-half to four times for a 10-fold increase in stretch velocity. Peak force was essentially independent of stretch velocity over this range. The reflex-burst frequency was not a function of the initial length of the muscle on the ascending limb of the length-tension relation. Active peak force (between two and three times passive peak force) was relatively constant over this range. The dynamic active stiffness (the resistance to stretch of the muscle when the nervous system was intact) was separated into two components. One component is that due to the tonic frequency of the motoneurons, the other to the reflex burst. The reflex component makes up a substantial part of the total active stiffness. Dynamic active stiffness is relatively constant under the conditions of these experiments and, when normalized, is similar to that observed in mammalian myotatic reflexes. This constancy, however, cannot be due to negative feedback control of stiffness, as in mammals. It is suggested that constant reflex stiffness arises from the combination of the low-pass filter characteristics of the muscle and the high-pass filter characteristics of the reflex over a restricted range of velocities.(ABSTRACT TRUNCATED AT 400 WORDS)

Generation and propagation of epileptiform discharges in a combined entorhinal cortex/hippocampal slice

1993 ◽  
Vol 70 (5) ◽  
pp. 1962-1974 ◽  
Author(s):  
A. Rafiq ◽  
R. J. DeLorenzo ◽  
D. A. Coulter
Keyword(s):  
Dentate Gyrus ◽  
Entorhinal Cortex ◽  
Mossy Fibers ◽  
Epileptiform Discharge ◽  
Intracellular Recordings ◽  
Tonic Component ◽  
Ca1 Neurons ◽  
Repeated Stimulation ◽  
Epileptiform Discharges ◽  
Reciprocal Connections

1. The development of epileptiform discharges in response to tetanic stimulation of the Schaeffer collaterals was studied by using extracellular field potential recordings in CA1, CA3, dentate gyrus, and entorhinal cortex and intracellular recordings in CA1 neurons in rat hippocampal-parahippocampal slices, which were cut so as to maintain reciprocal connections between entorhinal cortex and hippocampus in vitro. 2. The first type of epileptiform discharge to develop was an immediate afterdischarge, which grew in duration and amplitude with repeated stimulation trains at 10-min intervals, until it plateaued after five to nine trains at 40-s duration, on average. This afterdischarge, when fully developed, consisted of an early, high frequency tonic component, followed by a later, lower frequency clonic component. Fully developed primary afterdischarges were all-or-none, in that they had a definite threshold, and varied little in amplitude or duration when activated by threshold or suprathreshold stimulation. The primary discharge could be recorded simultaneously throughout the hippocampal-parahippocampal slice, providing evidence for the intact reciprocal connections between hippocampus and entorhinal cortex. Intracellular recordings in CA1 neurons revealed that during the tonic phase of the afterdischarge, neurons were depolarized by 15-30 mV and gradually repolarized during the clonic component. 3. After full development of the primary afterdischarge, a delayed secondary epileptiform discharge began to appear after five to nine stimulation trains. This late discharge began 2-5 min after the stimulation train and progressed in amplitude and duration with repeated stimulation, in some cases to 2-3 h long self-sustained epileptiform discharges. Like the primary afterdischarge, the secondary discharge could be recorded simultaneously throughout the hippocampal-parahippocampal slice, and individual bursts comprising the secondary discharge occurred at earliest latency in the dentate gyrus, followed by activation in CA3, CA1, and finally in the entorhinal cortex. Intracellular recordings in CA1 neurons established that the secondary discharge occurred without an accompanying depolarization. Rather, it appeared as synaptic bursts developing in an escalating frequency barrage, initiated 2-5 min after the primary afterdischarge. 4. Lesioning studies were conducted to begin determining the site of origin of the secondary epileptiform discharge. After appearance of the secondary discharge, the mossy fibers were cut. This lesion abolished the secondary discharge but did not block the primary afterdischarge. Moving the stimulating electrodes from the Schaeffer collaterals to the mossy fibers proximal to the cut reestablished a truncated secondary discharge. In a second lesioning experiment, a cut was made through the subicular region of the hippocampal-parahippocampal slice before the onset of stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

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