Academic literature on the topic 'Neuronal communication; Synapses'

The pharmacological interventions that constitute general anaesthesia are targeted at producing unconsciousness and an immobile patient even in response to noxious stimuli. Surgical anaesthesia also requires skeletal muscle relaxation, the degree of which depends on the site and nature of the surgical procedure. The anaesthetist therefore needs an advanced level of knowledge and understanding of the function of nerves, synapses, and muscle in order to understand, from first principles, how the drugs they use every day mediate their effects. Nerves and muscle cells are termed excitable cells be

‘Delivering the message: molecular communication’ explains how molecules can enable communication between cells and in synthetic systems. Hormones are biological messengers which can have short–term or long–term effects. When released into the bloodstream, they travel to the target cells and bind with transmembrane proteins, initiating a signal transduction relay inside the cell. Neurons cells carry electrical action potentials along the nervous system. At neuronal synapses, chemical neurotransmitters carry signals across the synaptic cleft and transfer them to the next neuron along. Supramolecular chemists aim to utilise or mimic signal transduction pathways in a range of applications, from pharmaceuticals to mechanical olfaction.

How information circulates in the brain was the subject of a heated debate lasting a decade or more among anatomists in the closing years of the last century. One camp argued that neural tissue consisted of a continuum, a syncytium, with no discernible functional units while the opposing view held that the brain consisted of discrete units, the nerve cells, communicating through point-to-point contacts that Sherrington dubbed synapses. Although in principle both views can be supported, in practice the majority of rapid communication occurs via specific point-to-point contacts, at either chemical and electrical synapses. Ephaptic transmission refers to nonsynaptic, electrical interactions between neurons. While such interactions do occur, for instance, among adjacent, parallel axons across the extracellular space, they are, by their very nature, neither very strong among any one pair of processes nor very specific. Their functional significance—if any—is currently not known, and we will not discuss them here (Traub and Miles, 1991; Jefferys, 1995). In the beginning chapter, we introduced the action of fast, chemical synapses. Given their importance, we will now return to this topic in greater depth. We first overview the pertinent biophysical events underlying chemical synaptic transmission and some of the vital statistics of synapses before we come to the mathematical treatment of synaptic input. In the last section, we will summarize our knowledge of electrical synapses and their computational role. Most typically, a synapse consists of a presynaptic axonal terminal and a postsynaptic process that can be located on a dendritic spine, on the trunk of a dendrite, or on the cell body. Figure 4.1 shows some examples of synapses among cortical cells as seen through a high-powered electron microscope. It is not easy at first to identify the synapses amid all the curved, irregular, and densely packed structures making up the neuronal tissue. In a number of locations, such as the retina or the thalamus, a synaptic connection is made between two dendrites, rather than between an axon and a dendrite. These synapses are called dendrodendritic synapses; they are believed to be relatively rare in the adult cortex. Most synapses are small and highly specialized features of the nervous system. As we will see, a chemical synapse converts a presynaptic electrical signal into a chemical signal and back into a postsynaptic electrical signal.

Communication between neurons occurs primarily at the level of synapses. The most common form of communication in the nervous system is through chemical synapses, which consist of presynaptic and postsynaptic components separated by a synaptic cleft. The presynaptic terminals contain synaptic vesicles, which are involved in the storage and release of neurotransmitters by the process of exocytosis. Complex mechanisms control the synthesis, vesicular storage, and release of neurotransmitters and regulate the availability of neurotransmitter at the level of the synaptic cleft. The effects of the neurochemical transmitter on its target are mediated by neurotransmitter receptors. Specific neurotransmitter systems are responsible for fast neuronal excitation or inhibition, while other neurotransmitter systems regulate the excitability of neurons in the nervous system. Abnormalities in neurochemical transmission are responsible for many disorders, including acute neuronal death, seizures, neurodegenerative disorders, and psychiatric diseases. Most importantly, neurochemical systems provide the target for pharmacologic treatment of these disorders. The aims of this chapter are to review the basis of neurochemical transmission and the distribution, biochemistry, and function of specific neurotransmitter systems.

Neurons are the cells of the brain responsible for intracellular and intercellular information transfer, or signaling; they are asymmetrical cells with morphologically and functionally distinct regions that specialize them for signaling. This chapter focuses on the unique structural elements characteristic of neurons throughout the animal kingdom. These include the dendrite, among whose functions is the receipt of information from other neurons. The axon, in contrast, is specialized for the intracellular transfer of information over long distances. The chapter concludes with a discussion of the synapse, the highly specialized structure that mediates the transfer of information from one neuron to another. It is this intracellular and intercellular communication that is the essence of nervous system function, and that makes the brain so complex and difficult to study and yet at the same time so fascinating for students of cell and molecular biology.

The research describes the mathematical modeling of a neuron and the possibility of its technical implementation. Unlike existing technical devices for implementing a neuron based on classical nodes oriented to binary processing, the proposed path is based on bit-parallel processing of numerical data (synapses) for obtaining result. The proposed approach of implementing a neuron can serve as a new elementary basis for the construction of neuron-based computers with a higher processing speed of biological information and good survivability. The research demonstrates the developed nervous circuit constructor and its usage in building of the nervous circuits of biological creatures and simulation of their work.