The human nervous system may be viewed as a three-stage system, as depicted in the block diagram of figure Central to the system is the brain, represented by the neural (nerve) net in figure, which continually receives information, perceives it, and makes appropriate decisions. Two sets of arrows are shown in figure. Those pointing from left to right indicate the forward transmission of information bearing signals through the system. On the other hand, the arrows pointing from right to left signify the presence of feedback in the system. The receptor in figure convert stimuli from the human body or the external environment into electrical impulses that convey information to the neural net (brain). The effectors, on the other hand, convert electrical impulses generated by the neural net into discernible reponses as system outputs.
In the brain there are both small scale and large scale anatomical organization, and different functions take place at lower and higher levels. Proceeding upward from synapses that represent the most fundamental level and that depend on molecules and ions for their action, we have neural microcircuits, dendritic trees, and then neurons. A neural microcircuit refers to an assembly of syanpses organized into patterns of connectivity so as to produce a funtional operation of interest.
A neural microcircuit may be likened to a silicon chip made up of an assembly of transistors. The smallest size of microcircuits is measured in micrometers, and their fastest speed of operation is measured in milliseconds. The neural microcircuits are groupedto form dendritic subunits within the dendritic trees of inividual neurons. The whole neuron, about 100 micrometers in size, contains several dendritic subunits. At the next level of complexity, we have local circuits made up of nurons with similar of different properties, these neural assemblies perform operation characteristic of a localized region in the brain.
In the brain there are both small scale and large scale anatomical organization, and different functions take place at lower and higher levels. Proceeding upward from synapses that represent the most fundamental level and that depend on molecules and ions for their action, we have neural microcircuits, dendritic trees, and then neurons. A neural microcircuit refers to an assembly of syanpses organized into patterns of connectivity so as to produce a funtional operation of interest.
A neural microcircuit may be likened to a silicon chip made up of an assembly of transistors. The smallest size of microcircuits is measured in micrometers, and their fastest speed of operation is measured in milliseconds. The neural microcircuits are groupedto form dendritic subunits within the dendritic trees of inividual neurons. The whole neuron, about 100 micrometers in size, contains several dendritic subunits. At the next level of complexity, we have local circuits made up of nurons with similar of different properties, these neural assemblies perform operation characteristic of a localized region in the brain.
