Architecture

The central nervous system (CNS) of vertebrates including man is organized in an ascending hierarchy of parallel structures-spinal cord, brain stem, and brain. The peripheral nervous system consists of peripheral nerves and the ganglia of the autonomic nervous system. Human brains contain about a hundred billion neurons. Evolution has caused a "cephalic" shift of importance, relative size, and control towards the higher centers or neocortex, which in man is larger and more complex than in other mammals. There are generalized similarities in structure, composition and functioning of central nervous systems in all vertebrates. Neurons within all nervous systems are themselves organized by their component cytoskeletons.

_Brain/Mind_

_consciousness, "self," "Mind's Eye," attention_

Brain Systems, Homunculi, "Centers" functionally related neurons, anatomical regions, assemblies of networks, reverberation_

Neural Synaptic Networks, Cartels, Modules_

cooperativity due to dense interconnectedness, parallelism, associative memory, learning, synaptic plasticity_

_Neuron_

multiple synaptic inputs and outputs, dendritic processing, _synaptic plasticity, axoplasmic transport_

_Cytoskeleton_

centrioles, microtubules, filaments, synaptic morphology, spatiotemporal cellular organization, cellular automata, coherent oscillations

_Cytoplasmic Ground Substance ("Infoplasm" )_

sol-gel states, geodesic actin, tensegrity structures, ordered water, dissipative patterns, holographic interference

Table 4-1: Collective hierarchy of parallel information processing systems.

Two types of cells make up nervous tissue: neurons and satellite cells. In the central nervous system, the satellite cells are called neuroglia and in the periphery, Schwann cells. These satellite cells wrap layers and layers of myelin sheeting around neurons forming what is generally considered to be merely insulation which increases the velocity of propagating signals.

The parts of a neuron are the dendrites, the cell body (or perikaryon) and the axon which is also referred to as the nerve "fiber." Dendrites and the cell body generally receive incoming signals and the cell body transforms these into an outgoing signal carried by the axon (Figure 4.1). The "white matter" of the central nervous system consists of fiber tracts and their myelinating glial cells while the

"gray matter" refers to clumps of cell bodies and dendrites known as "nuclei." A schematic diagram of brain functional organization is shown in Figure 4.2.

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