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Overview Of Neuron Structural And Functional Properties And Electric Circuit

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Overview Of Neuron Structural and Functional Properties and Electric Circuit Parameter Models from a Cellular Perspective.

Neurons serve the purpose of receiving signals coming from neighbouring neurons; they assimilate these signals, and generate nerve pulses. They then conduct and transmit these nerve pulses to other neurons which are capable of receiving them. Neurons are the structural constituents of the brain. Typically, neurons are five to six orders of magnitude slower than silicon logic gates. Neural events happen in the millisecond range as compared to events in silicon chip, which happen in the nanosecond range. However, the brain makes up for the relatively slow rate of operation of a neuron by having an astonishing number of them, 10 billion, to be more precise. And with a massive 60 trillion interconnections between them, the brain is truly a complex, non-linear, and parallel computer.

A neuron consists of the cell body, the dendrites, and the axon. The body of the cell contains the nucleus of the neuron. Each neuron has a hair-like structure of dendrites around it. They branch out into a tree-like form around the cell body. The dendrites are the principal receptors of the neuron and serve to connect its incoming signals. The axon is the outgoing connection for signals emitted by the neuron. It is a long cylindrical connection that carries impulses from the neuron. The connection between two neurons takes place at synapse, where they are separated by a synaptic gap of the order of one-hundredth of a micron. The signals reaching a synapse and received by dendrites are electrical impulses. It is assumed that a synapse is a simple connection that can impose excitation or inhibition, but not both on the receptive neuron.

Main parts of the Neuron

The principle of Space-Charge Neutrality states that in any given volume, the total charges of cations are approximately equal to the total charges of anions. This principle holds for most parts of living bodies except for that of plasma membrane due to the separation of charges across the membrane. And electrical potential is created because of this exception. Ions are usually uniformly distributed in the natural world but that is not the case in a biological system, such as the human body. The concentration of Na+, Cl-, and Ca2+ ions in most animal cells are lower than those in the extracellular space, but the extracellular K+ ions have the exact opposite properties. The difference in these ion concentrations and the existence of electrical potential are the driving forces behind the movement of ions, which determines intensity of the cross membrane currents. The Nernst-Planck equation (NPE) is most widely used for calculating the ion flux in neurophysiology. It describes the ionic current flow driven by electrochemical potentials and the passive behavior of ions in biological systems. This equation gives us insights of electric current flow across the membrane



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