Elements of a Feedback Loop

Summary

This video delves into feedback loops, explaining both positive and negative types. It highlights the key elements of feedback loops, such as receptors, effectors, stimuli, and responses, using examples like thermoregulation and blood glucose regulation. The presenter emphasizes the importance of understanding how these elements work together to maintain balance within a system. Through analogies like a speed sign and thermostat, the video illustrates how feedback loops function to keep systems, whether biological or mechanical, close to their set points.

Takeaways

• 🔁 Feedback loops are essential for maintaining stability in systems, both biological and non-biological.
• ➡️ A feedback loop is not complete until the output is fed back into the system, creating a loop.
• 👁️👣 In a feedback loop, receptors are typically in the middle, with effectors at the top and bottom, forming a figure-eight pattern.
• 🔍 Receptors and effectors are physical organs or parts of organs that play a crucial role in sensing and responding to stimuli.
• 🏃‍♂️🏃‍♀️ The stimulus is the change or condition that triggers a response, while the response is the action taken by the effector to counteract the stimulus.
• 🚦 An example of a feedback loop is the regulation of speed in response to speed limit signs, where the eyes act as receptors and the feet control the speed.
• 🌡️ Thermoregulation is a biological feedback loop where the hypothalamus senses body temperature and effectors like sweat glands and capillaries respond accordingly.
• 💉 Blood glucose regulation is another example of a feedback loop, with the pancreas as the receptor and insulin or glucagon as the response to high or low glucose levels.
• 🔋 Glucose is vital as it serves as the primary fuel for cells, making the regulation of blood glucose levels critical for cellular function.
• 🔄 Negative feedback loops are crucial for maintaining homeostasis by keeping variables close to a set point, ensuring the stability of internal conditions.

Q & A

What are the two main types of feedback loops mentioned in the script?

The two main types of feedback loops mentioned in the script are negative feedback loops and positive feedback loops.

What is the difference between a system with input and output and a feedback loop?

A system with input and output is not a feedback loop until the output is fed back into the system, creating a loop.

What are the key elements of a feedback loop?

The key elements of a feedback loop are the receptor, effector, stimulus, and response.

What role does the receptor play in a feedback loop?

The receptor, which is an organ, is located in the middle of the feedback loop and senses changes that trigger the feedback mechanism.

What is an effector in the context of a feedback loop?

An effector is an organ that responds to the stimulus by performing an action, such as the sweat glands or capillaries in thermoregulation.

How does the speed sign example illustrate a negative feedback loop?

The speed sign example illustrates a negative feedback loop by showing how a driver adjusts their speed based on the sign, with the goal of maintaining a constant speed close to the set limit.

What is the role of the thermostat in maintaining room temperature?

The thermostat acts as the receptor in a feedback loop, sensing the room temperature and triggering the furnace to turn on or off to maintain the desired temperature.

How does the hypothalamus function in thermoregulation?

The hypothalamus acts as the receptor in thermoregulation, sensing body temperature and triggering effectors like sweat glands and capillaries to respond by sweating or dilating to regulate body temperature.

What is the role of the pancreas in regulating blood glucose levels?

The pancreas contains beta and alpha cells that act as effectors in regulating blood glucose levels. Beta cells secrete insulin when glucose is high, and alpha cells release glucagon when glucose is low.

Why is it crucial to maintain blood glucose levels within a certain range?

Maintaining blood glucose levels within a certain range is crucial because glucose is the primary fuel for cells, and imbalances can lead to health issues.

How does the feedback loop help in keeping the body's set points stable?

The feedback loop helps keep the body's set points stable by constantly monitoring and responding to changes through receptors and effectors, ensuring the body maintains homeostasis.

Outlines

00:00

🔁 Understanding Feedback Loops

Mr. Andersen introduces the concept of feedback loops, emphasizing the distinction between negative and positive feedback loops. He mentions examples like thermoregulation and blood glucose regulation, and introduces the idea of a feedback loop as a system with input and output that forms a loop. The key elements of a feedback loop are discussed: receptors, effectors, stimulus, and response. Mr. Andersen uses the analogy of a speed sign to illustrate how feedback loops work, where the receptor is the eye, and the effectors are the actions of the feet to either slow down or speed up in response to the speed limit sign.

05:05

🌡️ Thermoregulation and Blood Glucose Regulation

This paragraph delves into the specifics of thermoregulation and blood glucose regulation as examples of feedback loops in biology. The hypothalamus is identified as the receptor for thermoregulation, with sweat glands and capillaries as effectors that respond to temperature changes by sweating or dilating to regulate body heat. For blood glucose regulation, the pancreas is the central organ, with beta and alpha cells responding to high or low glucose levels by secreting insulin or glucagon, respectively. These hormones help maintain blood glucose levels near a set point, ensuring the body has a steady supply of fuel for its cells.

Keywords

💡Feedback Loops

Feedback loops are systems in which the output of a process is fed back into the system as input, influencing the outcome. In the video, feedback loops are central to understanding how various biological and environmental systems maintain balance. The script discusses both negative and positive feedback loops, using examples like thermoregulation and blood glucose levels to illustrate how these loops help maintain stability.

💡Negative Feedback Loops

Negative feedback loops are a type of feedback loop where the output works to counteract or reduce the initial input, leading to a stable state. The video explains this concept using the example of a speed sign, where if a driver is going too fast, they will slow down, and if they are going too slow, they will speed up, maintaining a steady speed.

💡Positive Feedback Loops

Positive feedback loops are systems where the output reinforces the input, leading to an amplification of the initial effect. While not explicitly detailed in the script, they are contrasted with negative feedback loops to highlight the difference in how they affect the system's equilibrium.

💡Receptor

A receptor in the context of feedback loops is an organ or part of an organ that detects changes in the environment and initiates a response. In the video, the eye is used as an example of a receptor in a speed regulation feedback loop, detecting the speed and signaling the need to adjust it.

💡Effector

Effectors are organs or parts of organs that carry out a response to a stimulus. The script mentions feet as effectors in the speed regulation example, where the foot on the gas pedal either presses down to speed up or lifts to slow down in response to the stimulus detected by the receptor.

💡Stimulus

A stimulus in feedback loops is a change or event that triggers a response within the system. The video gives the example of driving at 38 miles per hour, which is faster than the desired speed, thus acting as a stimulus for the response to slow down.

💡Response

The response in a feedback loop is the action taken by the effector in reaction to the stimulus. In the context of the video, if the stimulus is driving too fast, the response is to slow down, which is an action taken by the effector (the foot on the brake pedal).

💡Set Point

The set point in feedback loops refers to the ideal or desired state that the system is trying to maintain. The video explains how feedback loops work to keep conditions, such as body temperature or blood glucose levels, close to their set points through the actions of receptors and effectors.

💡Hypothalamus

The hypothalamus is a part of the brain that acts as a receptor in the body's thermoregulation feedback loop. The video describes how the hypothalamus senses body temperature and initiates responses through effectors like sweat glands and capillaries to maintain a stable body temperature.

💡Pancreas

The pancreas is an organ that plays a crucial role in the blood glucose regulation feedback loop. As explained in the video, the pancreas contains cells that act as receptors, sensing blood glucose levels, and effectors, secreting insulin or glucagon to maintain the set point of blood glucose levels.

💡Insulin

Insulin is a hormone produced by the pancreas in response to high blood glucose levels. The video describes how insulin acts as a response in the feedback loop, allowing cells to take in glucose and thus lowering the blood glucose level back to the set point.

💡Glucagon

Glucagon is a hormone that is released by the pancreas when blood glucose levels are too low. The video explains that glucagon triggers the liver to convert glycogen into glucose, which is then released into the bloodstream, raising the blood glucose level back towards the set point.

Highlights

Introduction to feedback loops and their importance in biological and environmental systems.

Explanation of the difference between negative and positive feedback loops with examples like thermoregulation and blood glucose.

Discussion on the elements of a feedback loop, emphasizing the need for a loop to exist for feedback to occur.

Definition and role of a receptor in a feedback loop, positioned in the middle of the feedback loop model.

Definition and role of an effector, located at the top and bottom of the feedback loop figure eight model.

Importance of understanding the stimulus and response within a feedback loop for system regulation.

Practical example of a speed sign as a feedback loop to illustrate the concept of receptors and effectors.

Thermostat example to explain how a feedback loop works in maintaining room temperature.

Detailed explanation of thermoregulation as a feedback loop, with the hypothalamus as the receptor.

Role of sweat glands and capillaries as effectors in response to high body temperature.

Mechanism of how the body responds to low temperature through vasoconstriction and muscle shivering.

Importance of maintaining a set point in body temperature for overall health and homeostasis.

Introduction to blood glucose regulation as a feedback loop with the pancreas as the central receptor.

Function of beta cells in secreting insulin to lower high blood glucose levels.

Role of alpha cells and glucagon in raising low blood glucose levels by breaking down glycogen.

Emphasis on the critical role of glucose as a fuel for the body's cells and the necessity of its regulation.

Summary of the feedback loop elements and their importance in maintaining homeostasis in biological systems.

Transcripts

Hi. It's Mr. Andersen and today I'm going to go a little bit deeper into feedback loops

and talk about the elements of a feedback loop. You hopefully know the difference between

negative and positive feedback loops. And you could list a few like thermoregulation

and blood glucose. We'll add blood calcium as we go throughout the year. And there's

a number of feedback loops that control both inside of us and the outside of us. But I

want to talk about the elements. The important elements of a feedback loop so you're comfortable

with them. And so if we think of us as a system we're constantly getting input. And we're

constantly giving output. But that's not a feedback loop. A feedback loop doesn't really

exist until we take that output and that actually feed backs into the system. And so until we

have a loop then we really don't have a feedback loop. So what we're looking for are loops.

Now the terms should also be familiar with. In other words you should understand what

a receptor is and what an effector is. What a stimulus is and what a response is. And

if you've looked at any of the feedback loops in our book, you'll start to realize that

they have a similar pattern. In other words the receptor is always going to be in the

middle. And then you're going to kind of have a figure eight like this. So we're going to

have a figure eight. What happens if it goes up to high? What happens if it goes too low?

And so the receptor will always sit in the middle. And then the effector is going to

sit at the top. And the other effector is going to sit at the bottom. And so if we look

at these definitions, receptor and effector, they're organs. And so those are things. Physical

things. So the receptors and the effectors are going to be the top and the bottom of

the figure eight. And then these are actions. And so the stimulus and the response and the

stimulus and the response. So let's put some arrows like this. Those are going to be actions

on either side. In other words what it does or what it sends or what it's doing. And so

those are the elements of the feedback loop. And so not only should you know negative - positive.

You should be able to say what's the receptor. What's the effector? What's it doing? How's

it working. And so let's try that with a little bit of practice. And so the example I give

you as far as feedback loops go is one of these speed signs. And so when you see a speed

sign, then if you're going to fast you may slow down. And if you're going to slow you

may speed up. And so let's define some of the receptor and the effector. And so let's

do our little, let me get a color here. And so I'm going to put a receptor in the middle.

Now I could do a couple of feedback loops. But let's just deal with the person. And so

what's the receptor? Let's say the receptor is going to be your eye. It's going to be

in the middle. What is an effector? Let's say a foot up at the top and let's say your

foot down here below. So if I say those are the organs. So we're going to put an eye,

a foot and a foot at the bottom. So this is going to be my receptor and this is going

to be my effector on either side. And so if we talk about specifically what the stimulus

is, well let's say the stimulus is that you're going, I don't know, we'll say 38 miles an

hour, what's going to be your response. Your response is going to be slow down. Let's say

that you're all of a sudden going 22 miles an hour. So that's going to be the stimulus.

What's going to be the response? You're going to speed up. And so that will feedback to

the eye. And so what we're going to have is a feedback loop that's constantly going up

here and then down here and then up here. But it's kind of keeping you close to that

set point of that speed that we want it to be. And so we have a negative feedback, negative

feedback and it's kind of keeping you in that little center point. The example that your

book constantly talks about or all science books talk about is a thermostat. And it's

a great example. And so if we talk about how a thermostat keeps a room warm, well the thermostat,

so what are the nouns? What are the organs in this case? The thermostat is going to be

the receptor. So we're going to put that right in the middle. We're going to have a furnace

which is going to be an effector. And then we'd have another furnace up here. So let's

say that the temperature goes to high. So if the temperature goes to high, what is the

furnace going to do? The furnace is going to turn off. Let's say the temperature goes

too low. So that's an action, or a stimulus. What's our response going to be? Then it's

going to turn on. And so those are just analogies. Ways that you can understand how a feedback

loop works. But remember we're going to put the receptors and the effector and the top,

the bottom and right in the middle. And so that keeps us close to a set point. Now let's

try to do some real ones in biology. So let's try and do thermoregulation. So thermoregulation.

So we've got rid of their definitions over here. So we're going to put the receptor in

the middle. So the receptor in this case is called the hypothalamus. Hypothalamus is going

to be an organ. It's actually it a little bottom part of the brain that drips down from

the brain. A lower portion of the brain. It's connected to the pituitary. But the hypothalamus

is going to sense your temperature. So it's a organ. And so let's start with a receptor

right here in the middle. And you may want to start with temperature. Okay. So let's

say we get too hot. So let's say that our stimulus is the hypothalamus is getting too

hot. What are some effectors that we could put at the top? Well one example would be

like sweat glands. What's another one? Capillaries, like that. My handwriting is not great. So

let's say the temperature goes too high. Our organs at the top could be sweat glands, capillaries.

So if it goes too hot what are the sweat glands going to do, what's their response? Well they're

going to sweat. And that through evaporative cooling is going to lower our temperature.

What are the capillaries going to do? If they get too hot then they're going to dilate.

So there's more blood going by the surface of your body. And so that's going to release

more heat. And so that's going to lower our temperature as well. And so our response is

going to depend on what the effector is. Let's say that our temperature goes too low. What

are some things that could act down here. Well capillaries again. So if capillaries

before were dilating when we get too cold then they're going to constrict. And so what

that's going to do is hold more of your temperature close to the body. What's another one? Your

muscles for example. Our muscles could eventually start to shiver. And that's going to generate

a little bit of heat. We could have goose bumps where it holds our hair up on end which

doesn't really do much if you don't have a lot of hair. It's not like a dog. But it does

kind of pull your skin in tight like a coat pulling it tight. It's going to hold more

of that heat. And so this is our characteristic feedback loop where if it goes too high we

do these things. If it goes too low we do these things. And so that keeps our body temperature

near that set point right in the middle. Another example is blood glucose. So blood glucose,

if we think about that we should maybe set up the organs first. And so what would the

organ be in the middle? Well the organ is going to be the pancreas. So the pancreas,

let's put that right in the middle. What are we going to have if our blood glucose goes

too high? Well remember, the way I always do it is that we've got beta cells at the

top. And alpha cells at the bottom. Now what are those? Well inside the pancreas, if we

say the pancreas looks, it doesn't look anything like that. But the beta cells are going to

be speckled over the surface of the pancreas. They're parts of what are called the islet

of langerhans. And then we're going to have alpha cells as well speckled around here.

So they're sensing the blood glucose level. If the blood glucose level goes too high,

then what is our response? Well the beta cells are going to secrete insulin. And so what

does the insulin do? Insulin is going to hit insulin receptors on your cells. It's going

to open up these glucose transports. And glucose is going to start coming into the cell. Let's

say it goes too low, so if it goes too low, so this would be our stimulus. What's going

to happen? We're going to release something called glucagon. And what glucagon is going

to do is it's going to trigger the liver to breakdown glycogen into glucose and then release

that into the cells. And so we've got this great feedback loop which is going to keep

our blood glucose levels about perfect. Why is it important that we keep our blood glucose

levels perfect? It's because glucose is the fuel. And if we can't get that fuel to our

cells, or if we use too much of it too quickly, then we're out of luck. And so the whole thing

is built on this feedback loop where we constantly are keeping ourselves close to that set point

as far as blood glucose level goes. But remember the whole thing, let's find a different color,

is tied around these organs in the middle. So the receptors and the effecters. And then

the stimulus and the response. And so when you ever see one of these figure eight diagrams

in a book or anywhere, always be thinking back to the wonderful elements of a feedback

loop. Nouns. Actions. Organs. Actions. And I hope that's helpful.