What is a negative loop

Answer 1

I am answering this question under the assumption you meant negative feedback loops. I'm sorry if I'm mistaken.

In a biological system, like the human body, there are conditions in which the system works the best. However, things are always changing in and around the body, which means the body must make little tweaks to keep conditions consistent. These tweaks mean to keep all the parts of the body working the best are part of a process called "homeostasis".

As part of homeostasis, there are two kinds of feedback loops - positive and negative. They go through four steps: stimulus, signal, control, and effector. This means that something happens (stimulus), a signal is sent out indicating a move away from homeostasis (signal), a response happens and the responder checks to see if the problem is solved (control), and then the effector calls for more help if everything isn't fixed (effector). I'll give a few examples.

A positive feedback loop means, essentially, that the more something happens it ramps up the system until the best endpoint is reached. A great example of this is blood clotting - when you get a cut (stimulus), your skin sends signals out that you need to close the wound (signal). In response, clotting factors arrive to close the wound (control). If there aren't enough platelets to close the wound, the skin will continue sending out signals (effector). This is positive because it keeps happening.

A negative feedback loop essentially means that when a response to a stimulus happens,it's meant to decrease the system until the best endpoint is achieved. A classic example of this is thermoregulation. In this case, let's say you heat up from being in the sun and you've moved away from the optimal body temperature of 98.6 degrees Fahrenheit. Your brain send signals to your veins to dilate to release excess heat (signal). As you cool down, your brain will get updates on your body temperature from your blood (control) and as your temperature drops so will the vein dilation (effector).

I hope that helps!