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3 Dec 2025
•
Understanding Biology 2.2: Control and Communication
T
Timi Olanrewaju
@timiolanrewaju_
The Nervous System and Brain Structure
Think of your nervous system as your body's electrical wiring - it's made up of the central nervous system (CNS) (brain and spinal cord) plus all the other nerve cells throughout your body. Neurons are the specialised cells that carry electrical messages at lightning speed between different parts of your body.
There are three types of neurons that work like a relay team: sensory neurons carry messages from your senses to your CNS, interneurons connect sensory and motor neurons within the CNS, and motor neurons carry commands from your CNS to your muscles and organs.
Your brain has three key regions you need to know. The cerebrum handles your conscious thoughts, memory, and emotions - basically everything that makes you "you". The cerebellum keeps you balanced and coordinated so you don't fall over when walking. The medulla controls vital functions like breathing and heart rate without you having to think about it.
Quick Tip: Remember the brain regions by thinking C-C-M: Cerebrum for Consciousness, Cerebellum for Coordination, Medulla for Must-have functions like breathing!
Reflex Actions and the Reflex Arc
Reflex actions are your body's emergency response system - they're lightning-fast, automatic reactions that protect you from harm. When you touch something hot or blink when something flies towards your face, that's a reflex in action. These responses are involuntary and often bypass the brain entirely to save precious milliseconds.
The reflex arc follows a simple pathway: sensory neuron → interneuron → motor neuron (remember it as "SIM"). Between each neuron is a tiny gap called a synapse, where electrical signals are converted into chemical messages using neurotransmitters, then back to electrical signals in the next neuron.
How Reflex Actions Work
The reflex process is like a well-rehearsed emergency drill with five clear steps. First, a receptor detects the stimulus (like heat or pressure). Then an electrical impulse races along the sensory neuron to the spinal cord.
At each synapse, the electrical signal triggers the release of chemical neurotransmitters that jump the gap and restart the electrical signal in the next neuron. This happens twice - once between the sensory and interneuron, then between the interneuron and motor neuron.
Finally, when the signal reaches the muscle, neurotransmitters cause the muscle to contract and you pull away from danger. This whole process takes milliseconds - much faster than if your brain had to make a conscious decision!
Remember: The beauty of reflexes is that they happen automatically, leaving your conscious brain free to process what just happened after you're already safe.
Hormonal Control and Blood Glucose Regulation
While your nervous system handles rapid responses, your hormonal system manages longer-term control using chemical messengers called hormones. Endocrine glands release hormones into your bloodstream, where they travel to specific target cells that have the right receptors - like a key fitting into a lock.
Blood glucose regulation is a perfect example of hormonal control in action. Your pancreas acts like a glucose thermostat, releasing insulin when blood sugar is too high and glucagon when it's too low. Your liver serves as the glucose storage facility, converting excess glucose into glycogen for later use.
When glucose levels rise (after eating), insulin tells liver cells to absorb glucose and store it as glycogen. When levels drop (between meals), glucagon signals the liver to break down glycogen and release glucose back into the bloodstream. This keeps your blood sugar in the perfect range your cells need to function properly.
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Understanding Biology 2.2: Control and Communication
T
Timi Olanrewaju
@timiolanrewaju_
Your body is like a sophisticated control system that constantly monitors and responds to changes around you. The nervous and endocrine systems work together to keep everything running smoothly, from your heartbeat to your blood sugar levels.
The Nervous System and Brain Structure
Think of your nervous system as your body's electrical wiring - it's made up of the central nervous system (CNS) (brain and spinal cord) plus all the other nerve cells throughout your body. Neurons are the specialised cells that carry electrical messages at lightning speed between different parts of your body.
There are three types of neurons that work like a relay team: sensory neurons carry messages from your senses to your CNS, interneurons connect sensory and motor neurons within the CNS, and motor neurons carry commands from your CNS to your muscles and organs.
Your brain has three key regions you need to know. The cerebrum handles your conscious thoughts, memory, and emotions - basically everything that makes you "you". The cerebellum keeps you balanced and coordinated so you don't fall over when walking. The medulla controls vital functions like breathing and heart rate without you having to think about it.
Quick Tip: Remember the brain regions by thinking C-C-M: Cerebrum for Consciousness, Cerebellum for Coordination, Medulla for Must-have functions like breathing!
Reflex Actions and the Reflex Arc
Reflex actions are your body's emergency response system - they're lightning-fast, automatic reactions that protect you from harm. When you touch something hot or blink when something flies towards your face, that's a reflex in action. These responses are involuntary and often bypass the brain entirely to save precious milliseconds.
The reflex arc follows a simple pathway: sensory neuron → interneuron → motor neuron (remember it as "SIM"). Between each neuron is a tiny gap called a synapse, where electrical signals are converted into chemical messages using neurotransmitters, then back to electrical signals in the next neuron.
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How Reflex Actions Work
The reflex process is like a well-rehearsed emergency drill with five clear steps. First, a receptor detects the stimulus (like heat or pressure). Then an electrical impulse races along the sensory neuron to the spinal cord.
At each synapse, the electrical signal triggers the release of chemical neurotransmitters that jump the gap and restart the electrical signal in the next neuron. This happens twice - once between the sensory and interneuron, then between the interneuron and motor neuron.
Finally, when the signal reaches the muscle, neurotransmitters cause the muscle to contract and you pull away from danger. This whole process takes milliseconds - much faster than if your brain had to make a conscious decision!
Remember: The beauty of reflexes is that they happen automatically, leaving your conscious brain free to process what just happened after you're already safe.
Hormonal Control and Blood Glucose Regulation
While your nervous system handles rapid responses, your hormonal system manages longer-term control using chemical messengers called hormones. Endocrine glands release hormones into your bloodstream, where they travel to specific target cells that have the right receptors - like a key fitting into a lock.
Blood glucose regulation is a perfect example of hormonal control in action. Your pancreas acts like a glucose thermostat, releasing insulin when blood sugar is too high and glucagon when it's too low. Your liver serves as the glucose storage facility, converting excess glucose into glycogen for later use.
When glucose levels rise (after eating), insulin tells liver cells to absorb glucose and store it as glycogen. When levels drop (between meals), glucagon signals the liver to break down glycogen and release glucose back into the bloodstream. This keeps your blood sugar in the perfect range your cells need to function properly.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
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Is Knowunity really free of charge?
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Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user