what is the overall effect of a negative feedback mechanism
Negative feedback Whereas positive feedback tends to lead to instability via exponential growth, oscillation or chaotic behavior, negative feedback generally promotes stability. Negative feedback tends to promote a settling to equilibrium, and reduces the effects of perturbations. Negative feedback loops in which just the right amount of correction is applied with optimum timing can be very stable, accurate, and responsive.
Sodium channel Before an action potential occurs, the axonal membrane is at its normal resting potential, and Na+ channels are in their deactivated state, blocked on the extracellular side by their activation gates. In response to an electric current (in this case, an action potential), the activation gates open, allowing positively charged Na+ ions to flow into the neuron through the channels, and causing the voltage across the neuronal membrane to increase. Because the voltage across the membrane is initially negative, as its voltage increases to and past zero, it is said to depolarize. This increase in voltage constitutes the rising phase of an action potential.