What is a Positive Feedback Loop?
A positive feedback loop is like a chain reaction in your body. Unlike negative feedback that maintains balance, positive feedback amplifies a change, making things go even further away from normal before they return. It's like a snowball getting bigger as it rolls downhill.
How Does a Positive Feedback Loop Work?
Change Occurs: First, something changes in your body. This could be a specific event or condition going outside the normal range.
Detection: Your body notices this change and sends signals to intensify it, rather than counteract it.
Response: The response makes the change even more significant.
Amplification: This process continues until a specific goal is reached or a situation is resolved. Then, the loop stops.
Two Examples of Positive Feedback Loops in Humans:
Blood Clotting:
Change: You get a cut or injury, and your blood starts to flow out.
Detection: Platelets in your blood detect the injury and start sticking together at the wound site.
Response: The platelets release chemicals that signal more platelets to come and join the clotting process.
Amplification: As more platelets arrive, they reinforce the clot, making it bigger and stronger until the bleeding stops completely. Once the clot is secure, the positive feedback loop ends.
Normal Labor and Childbirth:
Change: A pregnant woman's body gets ready for childbirth.
Detection: The baby's head pressing against the cervix (the opening of the uterus) sends signals to the brain.
Response: The brain releases a hormone called oxytocin.
Amplification: Oxytocin makes the muscles of the uterus contract, pushing the baby further down. The more the baby pushes, the more oxytocin is released, leading to stronger contractions. This cycle continues until the baby is born. Once the baby is out, the positive feedback loop stops.
These examples show how positive feedback loops are like "accelerators" in the body, helping to intensify a particular process until a specific goal is achieved. In blood clotting, it stops bleeding, and in childbirth, it helps deliver the baby. Unlike negative feedback, which aims to maintain balance, positive feedback serves a purpose in situations where rapid change is necessary.
New York State Middle School Science Standards:
Standard MS-LS1-3: Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells. This standard relates to the explanation of how positive feedback loops work in the body.
New York State High School Biology Standards:
Standard HS-LS1-3: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. The text aligns with this standard by describing how positive feedback loops are a type of feedback mechanism.
Next Generation Science Standards (NGSS):
HS-LS1-3: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. The text aligns with this NGSS standard by explaining how feedback loops, including positive feedback, play a role in maintaining or changing the body's state.
New York State Next Generation Living Environment Standards (NYSSLS):
Standard LS1.D: Information Processing - In multicellular organisms, the individual cells that make up the organism are the units of structure and function. Each cell carries out the basic life functions, and the organism's functions depend on the collective activity of its cells. The text aligns with this standard by illustrating how cells in the body respond to changes through feedback mechanisms, including positive feedback.
Please note that while these standards align with the concept of feedback mechanisms, including positive feedback, the specific examples provided in the text may not be explicitly covered in all standards documents. Teachers should adapt and supplement their lessons based on their specific curriculum and standards requirements.