20Brain and Nerves

The environmental response mechanism of animals can be likened to that of general automatic machinery and signal processing machines, which can be divided into 3 steps: signal input, processing/integration, and operation/output. Sensory organs, or receptors, are the point of input of signals. Sensory organs encode the strength of the received stimulation in the form of frequency of excitation. These signals are then transmitted to different sensory cortices of the central nervous system according to the type of sensation. One important role of the central nervous system is to extract and process only those signals that have meaning out of all those received. It then passes on the processed information to areas that output the response, such as motor organs (e.g. muscle), secreting glands or luminous organs which are generally called effector or operating organs.

This chapter will describe the mechanism of the stimulation response of animals according to the order in which information is transmitted as mentioned above.

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