Chapter

The Simplest Nervous Systems

Larry W. Swanson

in Brain Architecture

Second edition

Published on behalf of Oxford University Press

Published in print August 2011 | ISBN: 9780195378580
Published online September 2012 | e-ISBN: 9780199965120 | DOI: http://dx.doi.org/10.1093/med/9780195378580.003.1017
The Simplest Nervous Systems

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Evolution is one way to understand nervous system architectural principles. Neurons first appeared during evolution in the radially symmetrical Cnidaria, where they are arranged in a nerve net. The neuron's basic structure and function have stayed remarkably constant throughout the rest of the animal kingdom, including in the human brain. Neurons in all animals can be divided into three fundamental types: sensory, motor, and interneurons. Generally speaking, information is transmitted along neurons and their three types of extensions (axon, dendrite, amacrine) via electrical impulses associated with the plasma membrane, whereas it is usually transmitted between neurons and other cells via chemical synapses that use a mixture of neurotransmitters (although some electrical synapses are known). What has evolved dramatically is the complexity of nervous system organization—not its individual units or neurons.

Chapter.  6390 words.  Illustrated.

Subjects: Development of the Nervous System

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