Brain

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ist in isolation: they also connect themselves to each other,forming the so-called neural chains, which transmit information to other neurons or muscles. The nerve impulses propagates throughout these chains.Two kinds of phenomena are involved in the nervous impulse: electric and chemical. The electrical events propagate a signal inside a neuron, and the chemical events transmit the signal from one neuron to another or to a muscle cell. The cell contact or junction between one neuron and the next, or between a neuron and a muscle cell is called synapse,which will be dealt with in future articles.
The nervous impulse
A nervous impulse is the transmission of an electric change along the membrane of a neuron beginning at the point of stimulus. The normal direction of the impulse in organism is from the body cell to the axon (see the article on the structure of the neuron on Brain & Mind issue # 7).
This nervous impulse or action potential,is a propagated, sudden and rapid change in transmembrane potential. Normally,as we have seen in the previous article in this series, the neuron membrane is polarized at rest, with a negative potential ( -70 mV). The action potential consists of a rapid reduction of the negativity of the membrane to 0mV and the inversion of this potential to values up to some +30mV, followed by a very quick return to value somehow more negative than the potential at rest of -70mV.


Potencial de ação exibido em um osciloscópio. The nervous impulse is known as action potential. The action potential is a phenomenon of electro-chemical nature and occurs due to the changes in the permeability in the neuron membrane. These changes in permeability allow the flow of ions from one side of the membrane to the other. Given that the ions are electrically charged particles, changes in the electric field generated by these charges take place.
One way we could visualize the action potential is by means of a thousand...