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Synapses
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Neurons communicate over the short term, that is, over time spans not exceeding a few hundred milliseconds, by means of electric signals that mostly involve synapses. But synapses are far from being just a means of transmitting electric signals between neurons and their target cells. By virtue of their properties, number, and spatial distribution, they play a major role in the processing of electric signals in the nervous system (Chapter 7). Moreover, synapses are considered by some to be the basic unit of storage of information in the brain. It is estimated that the brain has roughly 104 times as many synapses as neurons, that is, of the order of 1015 synapses.
The patient with acute neurological problems
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
Synapses can be electrical or chemical. Electrical synapses are found in cardiac muscle and the smooth muscle of the gastrointestinal (GI) tract, they also occur in the CNS. Electrical synapses are special channels directly connecting the cytoplasm of neighbouring cells. This allows the flow of ions between cells and accounts for the ‘wavelike’ muscular activity seen in cardiac contraction and gut motility. The rapid spread of electrical information ensures the entire muscle is synchronised and produces a coordinated contraction. Electrical synapses are faster than chemical synapses.
Exploring the types and manifestation of disorders
Published in Jane Hanley, Mark Williams, Fathers and Perinatal Mental Health, 2019
The cause of post-traumatic stress disorder is the only major mental disorder that is now understood. One of the major pathophysiological bases for PTSD is caused by multiple molecular pathways causing an excess of excitatory signalling. Synapses are junctions which allow a neuron to electrically or chemically transmit a signal from one cell to another. They can be excitatory or inhibitory. Inhibitory synapses decrease the probability of the firing action of a potential of a cell, whilst the excitatory synapses increase its likelihood, causing a positive action in potential neurons and cells. This excess signalling within the limbic system can lead to intense emotional reactions being triggered by traumatic events. This forces the logical part of the brain to process emotional information, making it more difficult to control thoughts. There is now increasing evidence to suggest that dopamine, responsible for motivation, reward prediction and addiction, is now crucial in the regulation of fear and anxiety (Amorapanth et al. 2000, Yehuda & LeDoux 2007, Glover et al. 2011).
The neurosciences at the Max Planck Institute for Biophysical Chemistry in Göttingen
Published in Journal of the History of the Neurosciences, 2023
Synapses are the points of contact between individual neurons and mediate the signal transfer in the nervous system. The term synapse was introduced in 1897 by the British neurophysiologist and later Nobel laureate Charles Sherrington (1857–1952), long before its structure and function were clarified (Valenstein 2005, 4) and, above all, against the bitter resistance of the so-called “reticularists,” who believed that nerve cells formed a syncytium (Nissl 1903). In the first half of the last century, first the functional roles of synapses were studied—that is, the chemical signal transmission by a neurotransmitter, its quantal release, and its effect on the postsynaptic nerve cells. When electron microscopy, which had been developed from the 1930s onward, came into use in 1954 (Hentschel 2014, 311; Ruska 1955), it became possible to examine the structure of the synapses, showing that they contained large quantities of small blisters known as vesicles and that the membranes are thickened at the contact points (Figure 3; see De Robertis 1964, 27–48; Cowan and Kandel 2001, 1–87).
A perspective on C. elegans neurodevelopment: from early visionaries to a booming neuroscience research
Published in Journal of Neurogenetics, 2020
Recent investigations reveal that nervous system plasticity also occurs at the connectome level. After its establishment, connectivity is plastic in response to internal or external states. Sulston described early that embryonic and postembryonic lineages showed different motoneurons, suggesting that circuit wiring changes developmentally (Sulston, 1976; Sulston et al., 1983; Sulston & Horvitz, 1977). Indeed, specific motoneurons undergo a switch in neuronal polarity, presynaptic and postsynaptic regions. In this edition, Cuentas-Condori and Miller (2020), review the mechanisms of this synaptic remodeling: the underlying mechanisms of transcription regulation, downstream cascades of protein recycling, microtubule dynamics, cell death, and extracellular interactions. Intriguingly, some implicated factors were initially isolated in Brenner’s screens (Brenner, 1974). Cuentas-Condori and Miller (2020) highlight early and recent research work that shapes our understanding of synapse refinement.
C. elegans MAGU-2/Mpp5 homolog regulates epidermal phagocytosis and synapse density
Published in Journal of Neurogenetics, 2020
Salvatore J. Cherra, Alexandr Goncharov, Daniela Boassa, Mark Ellisman, Yishi Jin
Synapses enable the transmission and integration of information within the nervous system. Proper synaptic connectivity is essential to govern nervous system functions such as sensory perception, learning, and coordinated movement. Aberrant synaptic connections have been associated with a variety of neurological disorders. Synapse formation, elimination, and maintenance work together to ensure precision and plasticity of neuronal circuits throughout the lifetime of an animal. Many neuronal-intrinsic mechanisms involve various classes of cell surface proteins and intracellular signaling pathways that establish synaptic connections (Cherra & Jin, 2015; de Wit & Ghosh, 2016; Sudhof, 2018). Additional work has shown how extrinsic mechanisms involving non-neuronal cells, such as astrocytes and microglia, cooperate with neurons to modulate neuronal circuits (Allen & Eroglu, 2017; Chung, Allen, & Eroglu, 2015). It is now well established that astrocytes and microglia play an active role in the pruning of synaptic connections during development of the visual system in mice (Chung et al., 2013; Stevens et al., 2007). In Drosophila, glial cells also remove synapses and axonal components as a means to eliminate neuronal connections (Awasaki et al., 2006; Fuentes-Medel et al., 2009).