0000000000172810
AUTHOR
R. A. Chaplain
Origin of impulse initiation in the slowly adapting stretch receptor of the crayfish
Characteristic for the crayfish stretch receptor is a gradual decrease in axon diameter up to a stretch of axon about 350 μm away from the soma-axon border. In response to depolarizing currents applied at different positions along the axon this stretch of axon can be localized as the most excitable membrane region. When depolarizing current steps of 10–25 nA intensity are injected into the soma the first impulse is always triggered in the soma (due to sudden rise in the membrane potential) while the second impulse originates at the axon region of highest escitability. As the intensity of the stimulus is increased the site of impulse initiation along the axon shifts nearer to the receptor so…
Metabolic control of respiratory neuronal activity and the accompanying changes in breathing movements of the rabbit
Expiratory-related neurons have been classified according to their phase relation within the respiratory cycle, their response to lung distension and collapse (α- and β-type), and to hyperventilation (tonic firing denoted by “+”, cessation of activity by “−”). The dorsal surface of the medulla oblongata was superfused with a metabolite-containing CSF solution and the activity of expiratory (E) and inspiratory-expiratory (IE) neurons was extracellularly recorded. The neuronal sub-types established by their functional behaviour could equally be distinguished by their differential response to one or several metabolites. In contrast to inspiratory (I) neurons, E − α , E + β , E − β and IE − β n…
Small-signal analysis of the encoder mechanism in the lobster stretch receptor and the frog and cat muscle spindle.
Ausgehend von der Leitwert-Potential-Beziehung als Bedingung fur die Impulsauslosung an erregbaren Membranen (Chaplain, 1974) wird eine Kleinsignal-Analyse des Kodierungsvorganges in Mechanorezeptoren beschrieben. Hierbei wird die Theorie der Systeme mit zeitvariablen Parametern angewendet. Das beschriebene mathematische Modell erlaubt quantitative Aussagen fur den Frequenzgang unabhangig davon ob die Momentafrequenz oder die Impulsdichte als Ausgangssignal betrachtet wird. Die Approximation experimenteller Daten gelingt sowohl fur die Ansteuerung des Kodierers bei intrazellularer Stromstimulierung im Fall des Dehnungsrezeptors wie auch durch Leitwertanderungen als Folge des mechano-elektri…
Ion conductance changes associated with spike adaptation in the rapidly adapting stretch receptor of the crayfish.
The time course of the repetitive impulse discharges has been investigated for two high intensities of maintained depolarizing currents, 30 nA and 50 nA, for which the receptor adaptation was complete within 70 msec. The changes in sodium and potassium conductance associated with the decline in spike activity have been analyzed at different instances of time by interrupting in successive experiments the various action potentials in the pulse trains either at the early phase by holding the potential at about -60 mV and recording the inward current (upstroke-gNa) or by evaluating the delayed outward current flowing as the result of a depolarizing voltage pulse which at the end of the action p…
Model predictions of the ionic mechanisms underlying the beating and bursting pacemaker characteristics of molluscan neurons
The general properties of the excitable membrane on molluscan pacemaker neurons can be described on the basis of a fair amount of experimental evidence available in the literature. The neuronal membrane exhibits under voltage clamp an initial inward current carried by both Na+ and Ca2+ ions, the time- and voltage-dependent characteristics of which are similar to that of other excitable structures. The conductance mechanism for the two ion species and the transport kinetics appear to be closely similar. The time course and amplitude of the delayed outward current carried by K+ ions shows a marked dependence on the membrane potential. Characteristic for the molluscan neurons is the existence …
On the contractile mechanism of insect fibrillar flight muscle. IV. A quantitative chemo-mechanical model.
Ausgehend von detaillierten Vorstellungen zur Kinetik der myofibrillaren ATPase und der Ankopplung der Enzymwirkung an die Mechanik der Myosinbruckenzyklen wird ein quantitatives chemo-mechanisches Modell fur den fibrillaren Insektenflugmuskel vorgeschlagen. Mit der Wahl eines einheitlichen Parametersatzes gelingt es praktisch alle bisher in der Literatur beschriebenen Resultate zu simulieren. Dazu gehoren der verzogerte Spannungsaufbau bei rechteckformigen und sinusoidalen Langenanderungen, charakteristische Nichtlinearitaten in den oszillatorischen Langen-Spannungsschleifen, die Aktivierung der ATPase Aktivitat durch statische und dynamische Dehnung, der proportionale Anstieg des Wirkungs…