Positive and negative feedback

Every day, on television or on social media, we regularly hear the word feedback or feedback accompanied by “negative or positive” or the expression “increased feedback or little feedback.” But do you know what the situation means or associate, the topic you are talking about at the end to understand its meaning? If you have doubts, don’t worry, you have opened the correct article, because at the end of the reading you will have much clearer ideas!

Positive feedback
Negative feedback
DefinitionIt promotes a change within a system.It is when the body tries to balance the effects that altered the system itself.
  • Promotes changes in the system
  • It occurs both in natural and social systems and in objects
  • External factors are needed to stop it
  • They can cause a vicious cycle
  • It is rare for it to happen in humans
  • Seeks to maintain balance in systems
  • It occurs in both natural and social systems and objects
  • No external factors are necessary
  • It is common in human biological processes


Relationship with homeostasis


It is practically unrelatedIt’s related
  • Blood clotting
  • Contractions in labor
  • Menstrual cycle
  • Body temperature regulation
  • Regulation of blood pressure
  • Regulation of blood pH

Definition of the word feedback

The word feedback can have several meanings and definitions, now we will give the most practical one that will make us really understand the definition of this word.

In technical and scientific language, feedback indicates the process by which the result of an action of the system is reflected in the system itself to correct or modify its behavior.
Regarding the etymology of the word “Feedback ” it is derived from the English verb feed, which means “enter, load” and return or “return.”

In nature, feedback means the ability of a system to regulate itself , taking into account the effects derived from the modification of the characteristics of the system itself. In living things, for example, negative and positive feedback systems are widely used to regulate homeostasis (the “normal” condition) of the body.

What is positive feedback

The positive feedback on amplifies change the possibilities of divergence of evolution is a mechanism for change, growth and gives the system the ability to reach new levels of balance because its objective is that the return system to its original state.

Characteristics of positive feedback

  • Produces changes in the state of a system.
  • It seldom occurs in the logical processes of an individual.
  • Exponential results.
  • It usually does not occur in the process of homeostasis.
  • Many times external factors are needed to stop it.
  • It degenerates the state of balance and can cause a vicious cycle.

Examples of positive feedback

Among the examples we can give of positive feedback is blood clotting. The blood stays fluid within the blood vessels. In the event of these ruptures, the clotting mechanism is immediately activated to prevent bleeding. A chain reaction of proteins forms that form a kind of mesh to seal the wound. So clotting is positive feedback.

Positive and negative feedback

In essence, negative feedback puts things the way they were before, positive feedback amplifies clutter to reach a new state of equilibrium. It literally means “to step back.” is the mechanism by which a system adjusts itself.To allow these parameters to stay within the limits of survival, the body uses two systems of:

  • Positive feedback
  • Negative feedback

While positive feedback allows a process to be accelerated or intensified after the stimuli received (as the initial stimulus increases, the final product tends to increase, as in a “vicious circle”), while negative feedback allows to produce a change opposite in the initial stimulus, which makes the final product of a process inhibit the process itself, this means that as the initial stimulus increases, the final product tends to decrease. The negative feedback is more widespread than positive .

What is negative feedback

The negative feedback helps maintain system stability, offsetting changes in the external environment. Thanks to feedback, organisms are kept in balance.

Negative feedback characteristics

  • Reduces the alterations that occur in organisms.
  • Recovers the original state of the system.
  • Non-exponential effects.
  • It can stop on its own when balance is restored.

Examples of negative feedback

To understand how negative feedback works , we take as an example erythropoietin or EPO, a glycoprotein hormone produced in humans mainly by the kidneys, whose main function is the regulation of the production of red blood cells by the bone marrow (called erythropoiesis’). Erythropoietin is important to maintain blood homeostasis, just think that in patients with chronic renal failure, the production of erythropoietin is reduced when determining the frequent anemia of these subjects.

  • Hypoxia (reduced O2 tension) occurs in the body
  • The endothelial cells of the peritubular capillaries of the kidney medulla detect the reduction in O2 tension;
  • They induce the peritubular fibroblasts to produce and release the EPO hormone into the systemic circulation;
  • The EPO hormone that acts at the level of the hematopoietic bone marrow by stimulating the erythroid progenitor cells CFU-E, reducing apoptosis and increasing their mitotic frequency, that is, a more rapid differentiation to proerythroblasts;
  • The end result of EPO stimulation in the bone marrow is an increase in the availability of red blood cells and hemoglobin.
  • The increased number of red cells can carry more oxygen by increasing the circulating O2 voltage and resolving the initial hypoxia.
  • When O2 tension returns to normal, the negative feedback mechanism causes a reduction in renal erythropoietin release.

Another example of negative feedback is insulin secretion (which is released whenever the blood sugar level is high, for example after a meal, only to have it no longer secreted when the blood glucose concentration returns to normal), or glucagon secretion (a hormone that is released whenever blood sugar is lower than normal and is no longer secreted when glucose concentration returns to normal).

Another example of negative feedback is maintaining a constant body temperature.

For instance:

  • When the body overheats, usually during intense physical activity, sweating begins.
  • The more the body temperature rises, the more sweating increases.
  • The more sweating increases and the lower the body temperature.
  • The lower the body temperature, the lower the sweating.
  • When the body temperature returns to normal levels, the vicious cycle stops and you stop sweating: if this does not happen, an overheated body would risk dehydration.

A final example of negative feedback occurs in the stomach, in fact, when there is too much HCl, this mechanism is established and gastrin production is inhibited.

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