Feedback

Many biologic processes are controlled by feedback, just as the temperature in a home from a furnace is regulated by a thermostat.

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1. In a given system, the return, as input, of some of the output, as a regulatory mechanism; e.g., regulation of a furnace by a thermostat. 2. An explanation for the learning of motor skills: sensory stimuli set up by muscle contractions modulate the activity of the motor system. 3. The feeling evoked by another person's reaction to oneself. See biofeedback.

- auditory f. the unwanted sound that occurs in an amplification system when the microphone picks up the sound from the speaker; a major problem in the use of hearing aid s.

- negative f. that which occurs if the sign or sense of the returned signal results in reduced amplification.

- positive f. that which occurs when the sign or sense of the returned signal results in increased amplification or leads to instability.

- tubuloglomerular f. a blood flow control mechanism operating in the kidneys that limits changes in glomerular filtration rate.

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feed·back 'fēd-.bak n

1) the return to the input of part of the output of a machine, system, or process (as for producing changes in an electronic circuit that improve performance or in an automatic control device that provide self-corrective action)

2 a) the partial reversion of the effects of a process to its source or to a preceding stage

b) the return to a point of origin of evaluative or corrective information about an action or process <patient \feedback was solicited> also the information so transmitted

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n.

the coupling of the output of a process to the input. Feedback mechanisms are important in regulating many physiological processes; for example, hormone output and enzyme-mediated reactions. In negative feedback, a rise in the output of a substance will inhibit a further increase in its production, either directly or indirectly (see negative feedback loops). In positive feedback, a rise in the output of a substance is associated with an increase in the output of another substance, either directly or indirectly.

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feed·back (fēdґbak) the return of some of the output of a system as input so as to exert some control in the process; see also endproduct inhibition, under inhibition.