Suzana Herculano-Houzel

Behavior with a nervous system becomes fast, flexible and complex

Two distribution systems allow large organisms to act as integrated wholes. One is the immunoendocrine system, which through the release of wide-acting substances in the circulatory system allows slow and lasting (stable) integration of bodily functions. The resulting integrated behaviors take seconds to minutes to occur, and last for hours to several days, as long as the substances released are still active. The other is…...

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Behaviour without a nervous system depends on diffusion

All actions, and therefore behaviors, require energy transfer. Behaviors happen as potential energy is dissipated, channeled through natural or man-made circuits, networks, or natural paths of least resistance. Ultimately, the source of energy is external to the system, and transferred to it in an original explosion (case of the solar system), through a power line or induction (appliances), or fuel (vehicles and…...

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Behavior is any observable action

We usually equate nervous systems with behaviors, but as it turns out, a nervous system – that is, an ensemble of organs and tissues made of excitable cells that carry signals rapidly across the body – is actually not necessary for behavior. If behavior is defined simply as sets of observable actions in a given context, then plants have behaviors, like orienting to sunlight; so do single-cell…...

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First Principles: Neuronal activity is contagious excitation, an electrochemical signal

“Activity” is a term that, in a neuron, usually describes the undoing of the voltage of their cell membrane. If such changes occurred in other cells, they would most likely soon be dead, intoxicated by high levels of calcium released from intracellular stores. In neurons, in contrast, either the undoing of the membrane potential is quickly reversed, or else it…...

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