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Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop which exacerbates the effects of a small disturbance. That is, the effects of a perturbation on a system include an increase in the magnitude of the perturbation. [ 1 ]
Any system can be drawn as a diagram set up with circles of causality – including actions, feedbacks and delays. [1] Reinforcing feedback (or amplifying feedback) accelerates the given trend of a process. If the trend is ascending, the reinforcing (positive) feedback will accelerate the growth. If the trend is descending, it will accelerate ...
The diagram consists of a set of words and arrows. Causal loop diagrams are accompanied by a narrative which describes the causally closed situation the CLD describes. Closed loops, or causal feedback loops, in the diagram are very important features of CLDs because they may help identify non-obvious vicious circles and virtuous circles.
A feedback loop is created when all or some portion of the output is fed back to the input. A device is said to be operating open loop if no output feedback is being employed and closed loop if feedback is being used. [45] When two or more amplifiers are cross-coupled using positive feedback, complex behaviors can be created.
An example of positive feedback is when a microphone picks up the sound that it is producing through a speaker, which is then played through the speaker, and so on. In addition to feedback, cybernetics is concerned with other forms of circular processes including: feedforward , recursion , and reflexivity .
Because all brain areas are bidirectionally coupled, these connections between brain areas form feedback loops. Positive feedback loops tend to cause oscillatory activity where frequency is inversely related to the delay time. An example of such a feedback loop is the connections between the thalamus and cortex – the thalamocortical radiations.
This bistability is most obvious in the transition between the follicular and luteal phases, and arises from interactions between positive and negative feedback loops involving GnRH, LH, FSH, estrogen, and progesterone. The kisspeptin system creates a switch-like mechanism driving the transition from negative to positive feedback.
The Hodgkin cycle represents a positive feedback loop in which an initial membrane depolarization leads to uncontrolled deflection of the membrane potential to near V Na. The initial depolarization must reach or surpass a certain threshold in order to activate voltage-gated Na + channels .