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Neural Networks
Published in Julio Sanchez, Maria P. Canton, Software Solutions for Engineers and Scientists, 2018
Julio Sanchez, Maria P. Canton
The neuron is an information processing unit that receives input signals from complex, and extremely large, tree-like elements called dendrites. The dendrites connect with the main body of the cell, called the soma. Located in the soma is the nucleus. Inputs from the dendrites, which can be excitatory or inhibitory, are collected in the soma. When the excitatory element of the input reaches a certain threshold level, the neuron fires and transmits an electrical signal along the axon. At the end of the axon there are the axonic endings, which are usually connected to the dendrites of other neurons. The space between the axon of one neuron and the dendrite of another one is called the synapse. A single neuron has from 1000 to 10,000 synapses. The excitement of the axonic ending of a neuron releases a chemical substance, called a neurotransmitter, that establishes the communication of information between neurons.
The Emergence of Order in Space
Published in Pier Luigi Gentili, Untangling Complex Systems, 2018
When the action potential reaches the synapsis, voltage-gated Ca+2 channels open and calcium ions enter the axon terminals. Ca+2 entry causes neurotransmitter-containing synaptic vesicles to move to the plasma membrane, fuse with it and release their content according to the process of exocytosis. The neurotransmitter diffuses and binds to ligand-gated ion channels of the dendrites of other neurons, exerting either an inhibitory or an excitatory action.
Adansonia digitata ameliorates lead-induced memory impairments in rats by reducing glutamate concentration and oxidative stress
Published in Egyptian Journal of Basic and Applied Sciences, 2022
Eduitem S. Otong, Sunday A. Musa, Barnabas Danborno, Sohnap J. Sambo, Nathan I. Dibal
Glutamate is the most abundant excitatory neurotransmitter; it activates more than 50% of the brain synapses and is responsible for learning and memory [14]. Previous studies report that Pb exposure can influence glutamate signaling that plays an important role in neuronal degeneration and cognition [15,16]. In the brain, astrocytes carry glutamate through excitatory amino acid transporter-2 (EAAT-2) and glutamate transporter-1 (GLUT-1) in humans and rodents, respectively [17,18]. Glutamate acts on ionotrophic receptors to enhance ion entry into cells that eventually trigger intracellular signaling. N-methyl-d-aspartate (NMDA), an ionotrophic receptor, plays an important role in the progress of neurodegenerative diseases. NMDA binds to glutamate and prompts ion influx at post-synaptic membrane, thereby linking pre-synaptic ad post-synaptic activation [19,20]. Lead was reported to affect glutamate by selective blockage of the N-methyl-D-aspartate (NMDA) receptor, responsible for neuronal plasticity and development [13].
Fatigue: Is it all neurochemistry?
Published in European Journal of Sport Science, 2018
Neurotransmitters are chemical compounds that act as messengers within our body and brain. They are released from nerve terminals into the synaptic cleft in order to bind receptor sites at a post-synaptic neuron in order to produce their effect that can be either inhibitory or excitatory. There is an abundance of different neurotransmitters that can be classified in different types such as amino acids, peptides and monoamines. Some examples of important neurotransmitters are serotonin, dopamine (DA), noradrenaline (NA), gamma-aminobutyric acid, glutamate, acetylcholine and adenosine. The present review will focus on the monoamines serotonin, DA and NA.
Inhibition of oxidative stress by testosterone improves synaptic plasticity in senescence accelerated mice
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Lu Wang, Juan-Hui Pei, Jian-Xin Jia, Jing Wang, Wei Song, Xin Fang, Zhi-Ping Cai, Dong-Sheng Huo, He Wang, Zhan-Jun Yang
Glutamate is the predominant excitatory neurotransmitter involved in numerous CNS functions especially in cortical and hippocampal regions (Perez-Otano and Ehlers 2005). Approximately 70% of all excitatory synapses in the CNS of mammalian brains utilize glutamate as a neurotransmitter. Glutamate receptors, in particular, N-methyl D-aspartate receptors (NMDARs) are excitatory glutamate ionotropic receptors involved in various physiological and pathological processes (Lau and Zukin 2007; Perez-Otano and Ehlers 2005) and play important roles in CNS excitability synaptic transmission, synaptic plasticity and cognitive processes. It is of interest that in AD there is reduction in number of glutamatergic neurotransmitters and synaptic plasticity, which subsequently led to abnormal activation of NMDARs (De Felice et al. 2007; Lacor et al. 2007), attributed to result in Ca2+-dependent signaling pathway disorder (Parameshwaran, Dhanasekaran, and Suppiramaniam 2008). Previously Jia et al. (2015) noted that T significantly increased protein expression levels of synaptic NMDAR, promoting Ca2+ entry into hippocampal cells and phosphorylation of mouse cAMP response element-binding protein. Similarly, treatment of castrated SAMP8 mice with T was found in our study to enhance the protein expression levels of NMDAR. It is worthwhile noted that T significantly elevated the protein expression levels of p-CaMK II suggesting that Ca2+ flux may be associated with the effectiveness of this male hormone in ameliorating AD symptoms. Indeed, Berridge and Irvine (1989) reported that elevated levels of intracellular Ca2+ enhanced the activity of CaMK which increased neuronal synaptic plasticity. Evidence thus indicates that T inhibits neurotoxicity by promoting neuronal survival and synaptic plasticity.