Hey YouTube! I was asked to explain the difference between negative and positive feedback loops along with some examples. So let's just jump right in.
I think the first step to knowing the difference between negative versus positive feedback loops is to understand why they occur. So why? Why does our body go through these mechanisms of feedback loops?
Well I have one word that should answer your question. Homeostasis. So what is homeostasis? Homeostasis is the stability of the body's internal environment and there are countless amounts of physiological processes that our bodies undergo every day to maintain the state of balance. The body's internal environment is made up of something we call variables.
These variables could be things like body temperature or the chemical components in our blood and other body fluids. And if one of these variables become imbalanced, we may begin to feel sick or imbalanced ourselves. For example, if we have too much sugar in our blood, we may begin to feel confused, dizzy, or even nauseated.
Here's another way you can look at it. Each cell in our bodies has a small amount of fluid surrounding it. If one of these variables, such as the amount of fluid surrounding the cell, or the chemical components in the fluid surrounding the cell, become too thick or too salty, it may be hard for that cell to function properly under those conditions. So our body must maintain internal stability. so the cells in our body can do their job properly.
Now let's talk about set points and normal range. All variables must remain at a set point, but because our bodies may sometimes fluctuate, no one's body can always remain at an exact set point at all times. So our bodies will maintain something called a normal range. One example is our blood's pH level. The blood usually maintains a pH level of 7.4.
This doesn't necessarily mean that the blood will always be at 7.4 exactly, but our blood may maintain a pH close to this value, usually around 7.35 to 7.45. If the blood pH stays within these values, it may not be a set point of 7.4, but it's okay because these values are still within normal homeostatic range. However, if the blood goes below or beyond these values, This could mean that the blood's pH level is out of normal range. So all of these variables in the body are closely watched and controlled so that they may stay at a normal range or value. Now, whenever a change in variable is detected, actions are triggered to bring the body back to homeostatic range.
This is done through, you guessed it, feedback loops. Feedback loops may be negative or positive. But most homeostatic mechanisms are carried out via negative feedback loops.
So what are negative feedback loops? Negative feedback loops work by opposing or moving away from whatever the change in variable is. Negative feedback loops reduce output and resist change to bring the body back to its normal homeostatic range. Maybe this depiction will help. If the change in variable is to the left, negative feedback is going to travel in the opposite direction.
to the right to reach homeostasis. Every negative feedback loop requires three main components, a receptor, a control center, and an effector. The receptor is what I like to call the receptionist because its function is to relay messages to the control center.
It also functions to monitor the body's internal condition. The control center receives information about the change in variable from the receptor and regulates the output of the effector. The control center is most likely to be cells in the brain or an endocrine gland.
The effector is going to cause the physiological response to the change in variable. The effector can be a cell or an organ. So let's go over how negative feedback loops work step by step, then after this we'll go over some examples.
When a regulated variable goes outside of its normal range, this is called a stimulus. This stimulus is detected by a cellular structure called a receptor. This receptor will then give this information to the control center.
The control center will then take the information that the receptor gave to it and compare the current value of the variable to its normal set point. Now if the control center does determine that the variable is out of its normal range, then the control center will send signals to the effector. The effector will initiate a physiological response to return the variable back to its normal homeostatic range.
Once the variable gets back to normal, the control center lets the effector get back to its normal routine. So now some examples. Let's start with blood pressure.
Let's say your blood pressure becomes really high. This piece of information is a stimulus that is detected by receptors in the blood vessels. The receptors will send this information over to the brain, which would be the control center.
After determining that your blood pressure is out of normal range, the control center will then send a message to the effector cells. The effectors in this scenario would be the heart and blood vessels. The effectors will work to decrease heart rate and increase the diameter of blood vessels, in turn causing blood pressure to fall back within its normal range.
or to its set point. Now let's say that your blood pressure was low instead of high. The effector would do the opposite.
The effector would instead increase the heart rate and decrease the blood vessel size and diameter. Let's go over another example of a negative feedback loop. Say you get cold and your body temperature begins to drop. This stimulus will be detected by the cells in your brain, which would be the control center. The control center will then compare your body temperature to its set point.
and determine that your temperature is out of its normal range. The brain cells or control center will then activate other nerve cells to send signals to your skeletal muscles. The skeletal muscles in this case will be the effector. The effector will cause you to shiver to increase body heat.
As a result, your temperature will begin to rise until it returns back to its normal homeostatic range. Afterwards, the stimulus ends and the brain cells or control center will stop sending signals to the effector. Now let's talk about positive feedback loops. Okay guys, so remember we said that negative feedback loops bring the body back to its normal homeostatic range by resisting or going against the change in variable. But positive feedback loops work differently.
They bring the body back to its normal homeostatic range by supporting or reinforcing the change in variable. I know it sounds weird, but let's try this depiction again. See, for example, the change in variable is to the right. Positive feedback loops will travel in that same direction, to the right.
Positive feedback travels in the direction of the change to bring the body back to its normal range. Positive feedback increases output, results in more of a product, and occurs when something needs to happen quickly. Labor is an interesting example of positive feedback. So the first contractions of labor push the baby's head against the cervix, which is the stimulus.
Stretch-sensitive nerve cells in the uterus would send messages to the control center in the brain, in turn causing the pituitary gland to release the oxytocin hormone. The oxytocin hormone will cause smooth muscles of the uterus, which would be the effector in this case, to increase contractions. As contractions push the baby further down the birth canal, the cervix will stretch even more.
And remember we said that positive feedback reinforces the initial change in variable, which would be the contractions and the stretching of the cervix. We also said that positive feedback results in more of something, which would be the oxytocin hormone. So this contracting and stretching of the cervix is going to get stronger and stronger and oxytocin release will increase more and more until the baby is born.
I mean think about it, if the body's trying to get back to homeostasis, negative feedback wouldn't really help this process. The body needs a quick and rapid response to deliver the baby out of the birth canal. Alright ladies and gents, that brings this video about negative versus positive feedback leaps to an end.
I really hope this video was helpful. Please be sure to like, comment, share, and subscribe. Remember to never give up and as always, thanks for watching.