We explain what positive and negative feedback are, the characteristics of each one and examples. Also, what is homeostasis.
What are positive and negative feedback?
Broadly speaking, feedback is the mechanism through which the results of a process or an activity are reinserted into the system that produces it to provide you with useful information when making decisions. In other words, it is a way of controlling a process, evaluating its results to know if it works more or less as expected.
The concept of feedback is used in very different areas, ranging from biology and physiology to arts and techniques. In general, it is a “loop” or “return”, that is, a dynamic in which a part of the result is redirected to the process itself.
That is, the two possible types of feedback lead to different scenarios:
- Negative feedback has a stabilizing effect on the system. It returns the information produced to the sender, so that they can correct the input pattern, and thus keeps the system working. This is what happens, for example, with factory quality control systems: a portion of the manufactured products do not go on sale, but are consumed internally to ensure that they meet minimum quality standards.
- Positive feedback has a creative, productive effect and pushes towards change. That is, it tends to increase the signal or activity, since by returning the information to the beginning, it enhances certain changes in the process. An example of this is the reinvestment of capital in a factory, in which the money obtained from the sale of products is spent on new machines that allow more products to be manufactured, in order to obtain more money and be able to improve the machines again.
Examples of positive and negative feedback
Once we understand the difference between positive and negative feedback, we can find other examples for each:
Examples of negative feedback :
- The refrigerator thermostat which measures the temperature continuously, and once the desired minimum is reached, it turns off the compressors and stops the cooling; and once the maximum allowed is reached, it turns them on again.
- The dynamics of teaching evaluation They serve to control how well the teaching dynamic works, since the class provides the teacher with the necessary information about the learning that takes place in it, and allows him to make adjustments to it.
- A user satisfaction survey provided by a company to its clientele so that they return to the company the information they consider about its operation.
- Medical examinations They draw our blood to see how healthy we are and with that information modify our diet or our lifestyle habits.
Examples of positive feedback :
- How semiconductors work whose capacity to conduct electricity is greater the higher its temperature. By conducting a greater electrical charge, an increase in temperature occurs, which allows the charge to be increased and so on, until the device is destroyed if no other process intervenes.
- A fishing facility It extracts a certain amount of food from the sea, with which it pays for its maintenance and obtains a surplus. If the latter is used to improve the facilities, it will be possible to fish more efficiently, increasing the money obtained and so on.
- The sound feedback unpleasant beeping characteristic of poorly placed microphones in a recording, occurs when the audio signal emitted by the speakers is captured by the microphone and emitted again, amplifying the sound until it becomes noise.
- How capacity multipliers work which are transistors configured to multiply the capacity of a capacitor, gaining current as it travels through the circuit. They are very common in electrical power supplies.
homeostasis
When the concept of feedback is applied to the human body and other living beings, it becomes evident that there are several processes designed to maintain the stability of the organism (that is, they are negative feedback processes), and others designed to increase its production of certain substances (positive feedback processes).
In both cases, the task is to allow the organism a vital adaptation to the environment. That is to say, Positive and negative feedback in the body seeks to maintain its homeostasis, its state of balance. which guarantees a more or less prolonged existence.
homeostasis It is an essential condition for life which all living beings share although through very different mechanisms. But from the tiniest microbe to large land mammals, they all need to regulate their bodily functioning through negative feedback and sometimes accelerate certain processes through positive feedback. For example:
Homeostasis through negative feedback :
- Body temperature of humans It must be kept in a very stable range so that its chemical processes occur unaltered. For this reason, there are temperature regulation mechanisms that are activated when it falls below what is acceptable (such as shivering, which generates muscle heat by repeatedly mobilizing the muscles, or the constriction of blood vessels to preserve blood heat), or when it rises above what is acceptable (such as sweating to cool the skin, or vasodilation to allow the blood to cool).
- When the oxygen demand of the body's tissues increases, for example, when we perform physical exercise, the body responds increasing blood pressure so that the flow of oxygen is greater. When this demand decreases, the pressure also decreases.
- Faced with a drastic decrease in the calories available to the body (that is, when someone is hungry), the body responds by trying decrease metabolic rate that is, slowing down energy consumption to delay the harmful effects of hunger. This is why people who try to lose weight through diets notice a slowdown in weight loss as the body compensates for the caloric decrease. The solution for this is to increase the need for calories, that is, to do physical exercise.
Homeostasis through positive feedback :
- During the final moments of human pregnancy the fully formed fetus has no space inside the womb and its head pushes against the cervix. The maternal body, instead of counteracting this effect, responds by producing oxytocin, a hormone that stimulates uterine contractions so that the fetus can be expelled quickly. These contractions push the fetus forward, stimulating the production of more oxytocin, and so on until delivery. Otherwise the birth would be long and agonizing and would put the mother's life at risk.
- Something similar happens during intercourse, that is, sexual relations . The nerve endings stimulated during genital contact trigger the production of sexual hormones that increase desire and feed back the process, increasing to lead to orgasm and correct fertilization. It is a positive process whose purpose is to create new life.
- Another example of this is accelerated digestion of certain proteins which once detected in the digestive tract trigger the production of digestive enzymes, allowing digestion to be a self-accelerated process: the greater the amount of digestible proteins, the greater the amount of enzymes that are secreted. Otherwise, digestion could take much longer than it should.
References
- “Feedback” on Wikipedia.
- “Positive feedback” on Wikipedia.
- “Negative feedback” on Wikipedia.
- “Positive and negative feedback” (video) in DJ Physiology.
- “Homeostasis” at the Faculty of Medicine of the National Autonomous University of Mexico (UNAM).
