Neural nets
Introduction

Neurons are basic elements of nervous system. They are life cells that are specialized in collecting, preserving, processing and transmitting information. There is a wide range of neuron types. In all types, the neuron consists of a body (soma), which gets information through input branches (dendrites) – a single neuron has about ten thousand dendrites – and which transmits the information through a single output (axon), which has a large number of branches at its end. The output signal of an axon corresponds to inputs that are processed inside the neuron. Therefore, the output of the neuron depends on inputs. The diameter of neuron's body varies. It may range from several μm to several tens of μm. The length of dendrites is two to three mm in maximum. On the other hand, the axon may be over one meter long.

In order to perform their function, neurons must be interconnected into neural networks inside the brain. Such interconnection is accomplished by dendrites that – by means of special projections (synapses) - connect to dendrites of other neurons or directly to bodies of other neurons, or even directly to axons in special cases. Intelligent and powerful behavior of the brain (neural networks in general) is given by perfect interconnection. Neurons of neural networks of the brain are arranged such that failure of one neuron cannot cause danger for the whole (due to combination of topological features and parallel processing).

Fig. 7.1: Live neuron