Nervous activities of the heart in Crustacea.
01 Jan 1961-Vol. 24, pp 287-311
TL;DR: Findings show that the cardiac rhythm arises not only at the cardiac ganglion but also at certain neurons in the ganglions.
Abstract: Crustacean cardiac rhythms, unlike those of vertebrates, do not originate in the heart muscle itself. Ganglion cells are normally located in the dorsal wall of the heart and the excitation for the heart beat starts at the ganglion. A neurogenic origin of the heart beat, however, was first demonstrated in Limulus by Carlson (1904). He applied a warm test tube on various parts of the heart muscle and ganglion and found that the cardiac rhythm was accelerated only when the tube was placed on a certain part of the ganglion (the fourth and fifth segments of the ganglion). If the ganglion was removed from the heart the beat stopped. These findings show that the cardiac rhythm arises not only at the cardiac ganglion but also at certain neurons in the ganglion.
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01 Mar 1974-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: The Stomatogastric ganglion of Panulirus interruptus contains about 30 neurons, and controls the movements of the lobster's stomach, and a group of six neurons which drive the stomach's lateral teeth are described.
Abstract: The Stomatogastric ganglion ofPanulirus interruptus contains about 30 neurons, and controls the movements of the lobster's stomach When experimentally isolated, the ganglion continues to generate complex rhythmic patterns of activity in its motor neurons which are similar to those seen in intact animals
275 citations
01 Jan 1977
224 citations
Cites background from "Nervous activities of the heart in ..."
...This has been well established in the case of the crustacean cardiac ganglion (Hagiwara, 1961; Hartline, 1967; Watanabe et ai., 1967)....
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..., the neural control of heart muscle in crustaceans (Hagiwara, 1961) and the neural control of respiration in lampreys (Rovainen, 1974), there is only one synergic class....
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01 Jun 1968
TL;DR: Model neural networks that simulate many aspects of the motor output to the flight muscles of flying locusts are discussed, including the simplest network model, which the authors believe simulates the locust flight-control system reasonably well.
Abstract: The motor output to the flight muscles of flying locusts is described briefly. Model neural networks that simulate many aspects of this output pattern are discussed. The model networks studied consisted of interconnected electronic analogs of unit patches of neural membrane. The analog units were designed by E. R. Lewis. The simplest network model, which we believe simulates the locust flight-control system reasonably well, consists of two groups of elements. The members of each group are mutually excitatory and produce bursts of impulses separated by rest periods. The two groups inhibit each other so that their bursts of activity alternate.
144 citations
TL;DR: The continuing relevance of the crustacean cardiac ganglion as a relatively simple model for pacemaking and central pattern generation is confirmed by the rapidly widening documentation of intrinsic potentials such as plateau potentials in neurons of all major animal groups.
Abstract: Investigations of the electrophysiology of crustacean cardiac ganglia over the last half-century are reviewed for their contributions to elucidating the cellular mechanisms and interactions by which a small (as few as nine cells) neuronal network accomplishes extremely reliable, rhythmical, patterned activation of muscular activity-in this case, beating of the neurogenic heart. This ganglion is thus a model for pacemaking and central pattern generation. Favorable anatomy has permitted voltage- and space-clamp analyses of voltage-dependent ionic currents that endow each neuron with the intrinsic ability to respond with rhythmical, patterned impulse activity to nonpatterned stimulation. The crustacean soma and initial axon segment do not support impulse generation but integrate input from stretch-sensitive dendrites and electrotonic and chemically mediated synapses on axonal processes in neuropils. The soma and initial axon produce a depolarization-activated, calcium-mediated, sustained potential, the "driver potential," so-called because it drives a train of impulses at the "trigger zone" of the axon. Extreme reliability results from redundancy and the electrotonic coupling and synaptic interaction among all the neurons. Complex modulation by central nervous system inputs and by neurohormones to adjust heart pumping to physiological demands has long been demonstrated, but much remains to be learned about the cellular and molecular mechanisms of action. The continuing relevance of the crustacean cardiac ganglion as a relatively simple model for pacemaking and central pattern generation is confirmed by the rapidly widening documentation of intrinsic potentials such as plateau potentials in neurons of all major animal groups. The suite of ionic currents (a slowly inactivating calcium current and various potassium currents, with variations) observed for the crustacean cardiac ganglion have been implicated in or proven to underlie a majority of the intrinsic potentials of neurons involved in pattern generation.
131 citations
TL;DR: Some of the methods employed for ensuring that the resting flight muscles receive an adequate supply of oxygen are discussed, with particular emphasis on the period immediately following flight.
Abstract: Publisher Summary Much of the success of insects is due to their effective solution of the two major physiological problems of water retention and oxygen supply. The oxygen supply to flight muscles that may metabolize aerobically at rates equaled only by certain bacteria is brought in through an elaborate system of tracheae and tracheoles, which in many species terminate alongside the mitochondria by means of indenting the cell walls. Ventilation arises from an endogenously produced rhythm in the central nervous system (CNS). In several insects the third embryonic abdominal ganglion may act as a pacemaker for the rhythm, regardless of whether it migrates to the thorax or remains in the abdomen. The action of proprioceptive and chemo receptive input on the pacemaker is variable in different species; in some, pacemaker activity is not strictly endogenous and ceases in the absence of input. In one-muscle spiracles activity is dually controlled from the CNS and at the periphery. The CNS acts largely by grading the response of the spiracle muscle to CO 2 . Movements of spiracles, synchronized with ventilation, are brought about by interneurones which run from ventilation centers and superimpose various patterns of activity on the free running or spontaneous behavior of the spiracle motor neurones. The pterothoracic tracheal system is much modified for flight. The pathway from a spiracle to the tracheoles is divided into primary, secondary, and tertiary sections, and the relative parts played by ventilation and diffusion in these sections in insects of different sizes are discussed. Finally, some of the methods employed for ensuring that the resting flight muscles receive an adequate supply of oxygen are discussed, with particular emphasis on the period immediately following flight.
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TL;DR: The stretch receptor organs of Alexandrowicz in lobster and crayfish possess sensory neurons which have their cell bodies in the periphery and it is concluded that, once threshold excitation is reached, the generator potential within slow cell dendrites is well maintained for the duration of stretch.
Abstract: The stretch receptor organs of Alexandrowicz in lobster and crayfish possess sensory neurons which have their cell bodies in the periphery. The cell bodies send dendrites into a fine nearby muscle strand and at the opposite pole they give rise to an axon running to the central nervous system. Mechanisms of excitation between dendrites, cell soma, and axon have been studied in completely isolated receptor structures with the cell components under visual observation. Two sensory neuron types were investigated, those which adapt rapidly to stretch, the fast cells, and those which adapt slowly, the slow cells. 1. Potentials recorded from the cell body of the neurons with intracellular leads gave resting potentials of 70 to 80 mv. and action potentials which in fresh preparations exceeded the resting potentials by about 10 to 20 mv. In some experiments chymotrypsin or trypsin was used to make cell impalement easier. They did not appreciably alter resting or action potentials. 2. It has been shown that normally excitation starts in the distal portion of dendrites which are depolarized by stretch deformation. The changed potential within the dendritic terminals can persist for the duration of stretch and is called the generator potential. Secondarily, by electrotonic spread, the generator potential reduces the resting potential of the nearby cell soma. This excitation spread between dendrites and soma is seen best during subthreshold excitation by relatively small stretches of normal cells. It is also seen during the whole range of receptor stretch in neurons in which nerve conduction has been blocked by an anesthetic. The electrotonic changes in the cells are graded, reflecting the magnitude and rate of rise of stretch, and presumably the changing levels of the generator potential. Thus in the present neurons the resting potential and the excitability level of the cell soma can be set and controlled over a wide range by local events within the dendrites. 3. Whenever stretch reduces the resting membrane potential, measured in the relaxed state in the cell body, by 8 to 12 mv. in slow cells and by 17 to 22 mv. in fast cells, conducted impulses are initiated. It is thought that in slow cells conducted impulses are initiated in the dendrites while in fast cells they arise in the cell body or near to it. In fresh preparations the speed of stretch does not appreciably influence the membrane threshold for discharges, while during developing fatigue the firing level is higher when extension is gradual. 4. Some of the specific neuron characteristics are: Fast receptor cells have a relatively high threshold to stretch. During prolonged stretch the depolarization of the cell soma is not well maintained, presumably due to a decline in the generator potential, resulting in cessation of discharges in less than a minute. This appears to be the basis of the relatively rapid adaptation. A residual subthreshold depolarization can persist for many minutes of stretch. Slow cells which resemble the sensory fibers of vertebrate spindles are excited by weak stretch. Their discharge rate remains remarkably constant for long periods. It is concluded that, once threshold excitation is reached, the generator potential within slow cell dendrites is well maintained for the duration of stretch. Possible reasons for differences in discharge properties between fast and slow cells are discussed. 5. If stretch of receptor cells is gradually continued above threshold, the discharge frequency first increases over a considerable range without an appreciable change in the firing level for discharges. Beyond that range the membrane threshold for conducted responses of the cell soma rises, the impulses become smaller, and partial conduction in the soma-axon boundary region occurs. At a critical depolarization level which may be maintained for many minutes, all conduction ceases. These overstretch phenomena are reversible and resemble cathodal block. 6. The following general scheme of excitation is proposed: stretch deformation of dendritic terminals --> generator potential --> electrotonic spread toward the cell soma (prepotential) --> dendrite-soma impulse --> axon impulse. 7. Following release of stretch a transient hyperpolarization of slow receptor cells was seen. This off effect is influenced by the speed of relaxation. 8. Membrane potential changes recorded in the cell bodies serve as very sensitive detectors of activity within the receptor muscle bundles, indicating the extent and time course of contractile events.
404 citations
274 citations