1 This chapter shows application of a consistent set of clear physical principles to describe the beginnings of the universe by the (hot) Big Bang model. The ultimate beginning presents difficulties for the physicist, particularly when it comes to explaining why we find a very inhomogeneous cosmos, instead of a uniform, radiating gas. Stars, globular clusters, galaxies, and clusters of galaxies dot space, but we cannot at present explain their presence without invoking a "deus ex machina." We expect ultimately to rationalize the existence of these local inhomogeneities through gravitational contractions of regions of higher than average mass density that in tum arise out of fluctuations, but the case cannot yet be made completely. Meanwhile, the Big Bang (incomplete) model deals with cosmic evolution in the large, as a balance between gravitational attraction and cosmic expansion. Its relationships are described by two simple equations derived from Einstein's theory of general relativity via local conservations of mass-energy and of momentum. Unfortunately, this model does not by itself produce the observed inhomogeneities. Neither the assumption of thermodynamic fluctuations following a "smooth" beginning nor that ofa chaotic beginning can itself account for stars and galaxies. A mystery remains. -THE EDITOR This chapter describes the efforts of cosmologists (and nature?) to form galactic and stellar structures, comments on them from the viewpoint of the homeokinetic principles (Soodak and Iberall, 1978) discussed elsewhere in this volume, and pursues some parallels in the origin of life. It appears that there are no serious problems in understanding the origin of stars, given the previous formation of a galactic gas mass. A number of reasonable, even likely, paths lead to star formation. On the other hand, the origin of inhomogeneities required to initiate galaxy formation is not yet known. Appendix 1 remarks on some advances in observational and theoretical cosmology made since the original writing of this chapter HARRY SOODAK • Department of Physics, The City College of New York, New York, New York

/pdf/self-organizing-systems-iqagjbi8lb.pdf

Self-Organizing Systems

https://www.cell.com/neuron/pdf/S0896-6273(04)00392-7.pdf

Differential Contribution of Pacemaker Properties to the Generation of Respiratory Rhythms during Normoxia and Hypoxia

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

Organization of the stomatogastric ganglion of the spiny lobster

Many of the motor neurons in the lobster (Panulirus interruptus) stomatogastric ganglion exhibit plateau potentials; that is, prolonged regenerative depolarizations resulting from active membrane properties, that drive the neurons to fire impulses during bursts. Plateaus are latent in isolated ganglia but are unmasked by central input. These findings emphasize the role of cellular properties as compared to synaptic wiring in the production of cyclic motor patterns by ensembles of neurons.

http://science.sciencemag.org/content/sci/200/4340/453.full.pdf

Bursting Neural Networks: A Reexamination

The central nervous system (CNS) must produce specific patterns of motor neuron impulses during a coordinated movement. The desire to understand how these patterns are produced and controlled has led investigators to examine the properties of interneurons within the CNS. A set of theoretical principles has emerged from these studies that are applicable to both invertebrates and vertebrates (Wilson 1967, Evarts et al 1971, Gurfinkel & Shik 1973, R. B. Stein et al 1973, Grillner 1975, Herman et al 1976, Shik&Orlovsky 1976, Wetzel & Stuart 1976, P. S. G. Stein 1977). This review will discuss how these principles apply to locomotion and will demon­ strate that they may also serve as useful working hypotheses in the study of other motor systems. The central hypothesis is that there is a neural pattern generator residing within the CNS that serves to produce the basic motor program (Wilson 1972). Informa­ tion derived from sensory input may modify the output of the pattern generator so that the motor output is adapted to the particular mechanical properties of the organism and its environment. The principles are the following:

Motor systems, with specific reference to the control of locomotion.

From somata of the pacemaker neurons in the Squilla heart ganglion, pacemaker potentials for the spontaneous periodic burst discharge are recorded with intracellular electrodes. The electrical activity is composed of slow potentials and superimposed spikes, and is divided into four types, which are: (a) "mammalian heart" type, (b) "slow generator" type, (c) "slow grower" type, and (d) "slow deficient" type. Since axons which are far from the somata do not produce slow potentials, the soma and dendrites must be where the slow potentials are generated. Hyperpolarization impedes generation of the slow potential, showing that it is an electrically excitable response. Membrane impedance increases on depolarization. Brief hyperpolarizing current can abolish the plateau but brief tetanic inhibitory fiber stimulation is more effective for the abolition. A single stimulus to the axon evokes the slow potential when the stimulus is applied some time after a previous burst. Repetitive stimuli to the axon are more effective in eliciting the slow potential, but the depolarization is not maintained on continuous stimulation. Synchronization of the slow potential among neurons is achieved by: (a) the electrotonic connections, with periodic change in resistance of the soma membrane, (b) active spread of the slow potential, and (c) synchronization through spikes.

/pdf/pacemaker-potentials-for-the-periodic-burst-discharge-in-the-3xgxrxb18q.pdf

Pacemaker potentials for the periodic burst discharge in the heart ganglion of a stomatopod, Squilla oratoria.

The pacemaker neurons of the heart ganglion are innervated from the CNS through two pairs of acceleratory nerves. The effect of acceleratory nerve stimulation was examined with intracellular electrodes from the pacemaker cells. The major effects on the pacemaker potential were an increase in the rate of rise of the spontaneous depolarization and in the duration of the plateau. The aftereffect of stimulation could last for minutes. No clear excitatory postsynaptic potential (EPSP) was observed, however. On high frequency stimulation, a small depolarizing response (the initial response) was sometimes observed, but the major postsynaptic event was the following slow depolarization, or the enhancement of the pacemaker potential (the late response). With hyperpolarization the initial response did not significantly change its amplitude, but the late response disappeared, showing that the latter has the property of the local response. The membrane conductance did not increase with acceleratory stimulation. The injection of depolarizing current increased the rate of rise of the spontaneous depolarization, but only slightly in comparison with acceleratory stimulation, and did not increase the burst duration. It is concluded that the acceleratory effect is not mediated by the EPSP but is due to a direct action of the transmitter on the pacemaker membrane.

https://rupress.org/jgp/article-pdf/54/2/212/1244607/212.pdf

Acceleratory Synapses on Pacemaker Neurons in the Heart Ganglion of a Stomatopod, Squilla oratoria

In the Squilla heart ganglion, the pacemaker is located in the rostral group of cells. After spontaneous firing ceased, the electrophysiological properties of these cells were examined with intracellular electrodes. Cells respond to electrical stimuli with all-or-none action potentials. Direct stimulation by strong currents decreases the size of action potentials. Comparison with action potentials caused by axonal stimulation and analysis of time relations indicate that with stronger currents the soma membrane is directly stimulated whereas with weaker currents the impulse first arises in the axon and then invades the soma. Spikes evoked in a neuron spread into all other neurons. Adjacent cells are interconnected by electrotonic connections. Histologically axons are tied with the side-junction. B spikes of adjacent cells are blocked simultaneously by hyperpolarization or by repetitive stimulation. Experiments show that under such circumstances the B spike is not directly elicited from the A spike but is evoked by invasion of an impulse or electrotonic potential from adjacent cells. On rostral stimulation a small prepotential precedes the main spike. It is interpreted as an action potential from dendrites.

/pdf/electrical-properties-of-the-pacemaker-neurons-in-the-heart-mhonhrsj34.pdf

Shosaku Obara

Papers

Pacemaker potentials for the periodic burst discharge in the heart ganglion of a stomatopod, Squilla oratoria.

Acceleratory Synapses on Pacemaker Neurons in the Heart Ganglion of a Stomatopod, Squilla oratoria

Electrical properties of the pacemaker neurons in the heart ganglion of a stomatopod, Squilla oratoria.