Feedback mechanism
A feedback mechanism, or feedback loop, is a fundamental concept observed across various fields, including economics, biology, engineering, and psychology. It refers to the process by which outputs of a system are fed back into the system as inputs, influencing its future behavior. There are two primary types of feedback loops: negative and positive. Negative feedback loops are regulatory systems that work to stabilize and maintain a consistent state by counteracting changes, such as thermostats in heating systems or blood pressure regulation in the human body. In contrast, positive feedback loops amplify changes and drive systems toward extremes, often seen in scenarios like childbirth, where hormone release intensifies contractions, or in global climate change, where initial warming leads to further ice melt and greenhouse gas release. Understanding these mechanisms is crucial for examining how systems respond to stimuli and maintain balance or undergo transformation.
Feedback mechanism
Feedback mechanisms, also called feedback loops, are common logical patterns. They can be found in almost all disciplines, including economics, physiology, engineering, and psychology. There are two types of feedback loops: negative feedback loops and positive feedback loops. In this instance, negative does not mean bad, and positive does not mean good. Negative loops tend to regulate and stabilize a system while positive loops tend to spiral until a dramatic change occurs. Common examples of negative feedback loops include thermostats and the systems that maintain blood pressure in humans. Common examples of positive feedback loops include the human immune system and global climate change.
Negative Feedback Loops
Negative feedback loops are regulatory mechanisms common in engineering and biology. Typically, they are used by systems to maintain a consistent state and work to minimize the impact of external stimuli. Negative feedback loops have several parts. First, they have something they seek to maintain. This target is the set point. They also have a sensor, which monitors the set point. Additionally, they have effectors, which modify the set point. Lastly, negative feedback loops have an integrating center, which controls the effectors and receives input from the sensors.
When a negative feedback loop is functioning properly, all its parts work in harmony. The sensors monitor the set point. When the set point moves away from its target, the sensors report that information to the integrating center. The integrating center activates the effectors, which move the set point closer to its target. This process repeats until the set point is at its target.
Automated thermostats are a common example of a negative feedback loop. Suppose a thermostat is set to keep a room at seventy degrees. Then, someone leaves a door open on a cold day. This serves as the stimulus. The room's temperature quickly drops to sixty degrees. The sensors report this to the computer, which is the integrating center. The computer turns on the heaters, which are the effectors. The heaters bring the room temperature up to sixty-three degrees. The sensors continue to report that the room temperature is not at the set point, and the process repeats until the room temperature returns to seventy degrees. Lastly, the sensors stop reporting that the room temperature is incorrect, and the integrating center turns off the effectors.
Homeostasis, the process by which the human body regulates itself, is maintained through a series of negative feedback loops. When blood pressure falls, sensory nerve fibers send signals to the medulla oblongata in the brain. The medulla oblongata activates motor nerve fibers, which increase the heart rate. This raises the blood pressure. In this scenario, the set point is the intended amount of blood pressure, the stimulus is whatever caused it to drop, the sensory nerves are the sensors, the motor nerve fibers and heart muscles are the effectors, and the medulla oblongata is the integrating center.
Positive Feedback Loops
Positive feedback loops function differently than negative feedback loops. Positive feedback loops have no set point. While negative feedback loops return something to a status quo, positive feedback loops accelerate until whatever caused them is gone. Just like negative feedback loops, positive feedback loops can be found in the human body. However, they are normally reserved for potentially life-threatening situations.
In a positive feedback loop, the effectors deployed in response to a stimulus cause each other to increase in intensity until either the stimulus or the effectors are eliminated. Hormonal reactions with contractions during a pregnancy are a good example of a positive feedback loop. During pregnancy, contractions in response to the stimulus (the infant ready to be born) activate nerves that tell the body to release the hormone oxytocin. Oxytocin, in turn, causes the body to increase the rate and intensity of the contractions. Faster and more intense contractions increase the rate of oxytocin release, which further increases the rate of contractions. This positive feedback loop continues to grow in intensity until the baby is born. At this point, the stimulus has been removed, and the positive feedback loop ends.
Blood clotting is another common positive feedback loop found in the human body. Blood clotting stops cuts from bleeding. Ruptured blood vessels release chemicals that attract platelets, which are tiny particles in the blood that clump together against the ruptured blood vessel. When clumped together, platelets release more of the chemical that attracts platelets. This process accelerates until the clumped platelets have completely sealed the ruptured blood vessel, removing the stimulus.
Because positive feedback loops accelerate themselves instead of regulating a system, they have the potential to be extremely damaging to the system itself. One commonly cited example of this phenomenon is global climate change. The global ice caps normally reflect a great deal of light and heat back into space. Without them, this heat stays on Earth. Global ice caps also trap a significant amount of greenhouse gases underneath their ice. When released into the atmosphere, greenhouse gases cause Earth to retain more heat.
When humans began releasing greenhouse gases into the atmosphere, they began a disastrous positive feedback loop. The first greenhouse gases released by humans increased Earth's average temperature at the global ice caps. This caused some of the ice caps to melt. Because there was less ice, less heat was reflected back into space, making Earth warmer. As Earth became even warmer, more of the ice caps melted, releasing the greenhouse gas trapped under the ice and warming Earth even more. Unless humans manage to break the positive feedback loop, this process will continue to accelerate until the global ice caps have completely melted, and Earth reaches a new stable state at a higher temperature.
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