Modeling Techniques Quantitative Representation of Fundamental Processes Feedback - Definitions Occurs whenever a variable influences its own dynamics. Positive feedback occurs when increasing a variables' value increases the rate of change of the variable. Negative feedback occurs when increasing a variables' value decreases the rate of change of the variable. Self-inhibition is a form of direct negative feedback.
Extrinsic factors can result in negative feedback.
Depending on the saturation level of the receiving sites, the effect can be either positive or negative. The result is that the reaction rate varies between zero and some maximum value. This is known as Hollings disc equation . If a particular process involves multiple driving processes, it is sometimes appropriate to combine the effects as a product relationship. More sophisticated mechanisms for combine the effects of several factors are available.