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What a plant or animal does
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The organ that serves as the primary control center of the nervous system in all vertebrate and most invertebrate animals
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A chemical that enters the body
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Signals that enter the body in the form of electromagnetic stimuli
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Signals that enter the body through physical touch or vibration
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A cell specialized for transmitting fast electrochemical signals
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A nerve ending that sends signals to the central nervous system when it is stimulated
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An action or condition that provokes a response