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Responding to change (a2 only)
Infection and response
Homeostasis and response
Energy transfers (a2 only)
Cell biology
Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
Organisation
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
Inter-war germany
Medieval period: 1066 -1509
2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
2m wars and welfare: britain in transition, 1906-1957
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
World war one
Britain: 1509 -1745
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12 Dec 2025
•
Nia
@nia_pfkb
Your muscles and bones work together like a perfectly coordinated... Show more






Ever wonder how your body manages to move so smoothly? Your skeletal system does way more than just hold you upright - it stores minerals, protects your vital organs, produces blood cells, and creates the framework for movement.
The real magic happens when your muscular system teams up with your bones. Muscles pull on bones through tendons to create movement, but they're also busy maintaining your posture, helping you breathe through intercostal muscles, and even producing heat to keep your body temperature stable.
Think of major bones like your femur (thigh), humerus (upper arm), and tibia (shin) as the framework, while muscles like anchors that create the pulling power. The smaller bones in your hands (carpals, metacarpals, phalanges) and feet (tarsals, metatarsals) work together for precise movements.
Quick Tip: Remember SSPPMM for skeletal functions - Support, Structure, Protection, Production, Mineral storage, Movement!

Understanding how your body moves is simpler than it looks - every movement happens through one of three planes of movement. The sagittal plane splits you into left and right halves, allowing forward/backward movements like flexion and extension. The frontal plane divides front and back, creating sideways movements like abduction (away from body) and adduction (towards body).
The transverse plane cuts you into upper and lower sections for rotational movements. Each plane works with a specific axis of rotation - think of these as invisible rods your body parts rotate around during movement.
Your joints determine what movements are possible. Hinge joints like your elbow and knee only allow flexion and extension, while ball-and-socket joints at your shoulder and hip are movement superstars, allowing almost every type of motion including horizontal abduction and adduction.
Memory Hack: "Some-sagittal, Fun-frontal, Too-transverse" and "Times-transverse, Starts-sagittal, Late-longitudinal" for planes and axes!

Your shoulder joint is the ultimate multitasker with the largest range of movement. Four key muscles make this possible: the deltoid handles abduction, pectoralis major controls flexion and adduction, while teres minor and latissimus dorsi work together for extension and various other movements.
The elbow keeps things simple as a hinge joint. Just two main players here - biceps brachii for flexion (bending) and triceps brachii for extension (straightening). All elbow movements occur in the sagittal plane around the transverse axis.
Your hip joint mirrors the shoulder's versatility as another ball-and-socket joint. The gluteus maximus, medius, and minimus work alongside muscles like iliopsoas and the adductor group to create the full range of hip movements essential for walking, running, and jumping.
Sport Connection: Understanding these muscle groups helps explain why footballers need strong glutes for powerful kicks and swimmers need flexible shoulders for efficient strokes!

Muscles never work alone - they operate in antagonistic pairs where one muscle contracts while its partner relaxes. When you bend your elbow, your biceps acts as the agonist (the muscle doing the work) while your triceps becomes the antagonist (the relaxing muscle). These roles flip when you straighten your arm.
There are three types of muscle contractions you need to know. Isometric contractions happen when muscles contract without changing length - think planks or wall sits where you're holding position. Isotonic contractions involve muscle length changes during movement.
Isotonic concentric contractions shorten the muscle (like lifting weights up), while isotonic eccentric contractions lengthen the muscle under tension (like slowly lowering weights down). Eccentric contractions are crucial for controlling movement and preventing injury.
Real Example: During a bicep curl, lifting the weight uses concentric contraction, while slowly lowering it uses eccentric contraction - both are equally important for strength building!

Analysing sporting movements becomes straightforward once you understand the basics. During the drive phase of sprinting, your ankle performs plantar flexion (pointing toes) using the gastrocnemius, your knee extends via the quadriceps, and your hip extends through the powerful gluteus maximus - all using concentric contractions.
In javelin throwing, the preparation phase involves elbow extension (triceps working concentrically) and shoulder abduction (deltoid contracting). The pull-back phase of kicking shows your ankle in plantar flexion, knee flexing through hamstring contraction, and hip extending via the glutes.
Each movement analysis requires identifying the joint type , the specific movement occurring, which muscles are the agonist and antagonist, and what type of contraction is happening. This systematic approach works for any sporting action.
Exam Success: Practice analysing everyday movements like walking upstairs or throwing a ball - the more you apply these concepts, the easier they become to spot in exam questions!
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Quotes from every main character
App Store
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
Nia
@nia_pfkb
Your muscles and bones work together like a perfectly coordinated team to create every movement you make. Understanding how joints move through different planes and which muscles are responsible will help you analyse any sporting action with confidence.

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Improve your grades
Join milions of students
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Ever wonder how your body manages to move so smoothly? Your skeletal system does way more than just hold you upright - it stores minerals, protects your vital organs, produces blood cells, and creates the framework for movement.
The real magic happens when your muscular system teams up with your bones. Muscles pull on bones through tendons to create movement, but they're also busy maintaining your posture, helping you breathe through intercostal muscles, and even producing heat to keep your body temperature stable.
Think of major bones like your femur (thigh), humerus (upper arm), and tibia (shin) as the framework, while muscles like anchors that create the pulling power. The smaller bones in your hands (carpals, metacarpals, phalanges) and feet (tarsals, metatarsals) work together for precise movements.
Quick Tip: Remember SSPPMM for skeletal functions - Support, Structure, Protection, Production, Mineral storage, Movement!

Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Understanding how your body moves is simpler than it looks - every movement happens through one of three planes of movement. The sagittal plane splits you into left and right halves, allowing forward/backward movements like flexion and extension. The frontal plane divides front and back, creating sideways movements like abduction (away from body) and adduction (towards body).
The transverse plane cuts you into upper and lower sections for rotational movements. Each plane works with a specific axis of rotation - think of these as invisible rods your body parts rotate around during movement.
Your joints determine what movements are possible. Hinge joints like your elbow and knee only allow flexion and extension, while ball-and-socket joints at your shoulder and hip are movement superstars, allowing almost every type of motion including horizontal abduction and adduction.
Memory Hack: "Some-sagittal, Fun-frontal, Too-transverse" and "Times-transverse, Starts-sagittal, Late-longitudinal" for planes and axes!

Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your shoulder joint is the ultimate multitasker with the largest range of movement. Four key muscles make this possible: the deltoid handles abduction, pectoralis major controls flexion and adduction, while teres minor and latissimus dorsi work together for extension and various other movements.
The elbow keeps things simple as a hinge joint. Just two main players here - biceps brachii for flexion (bending) and triceps brachii for extension (straightening). All elbow movements occur in the sagittal plane around the transverse axis.
Your hip joint mirrors the shoulder's versatility as another ball-and-socket joint. The gluteus maximus, medius, and minimus work alongside muscles like iliopsoas and the adductor group to create the full range of hip movements essential for walking, running, and jumping.
Sport Connection: Understanding these muscle groups helps explain why footballers need strong glutes for powerful kicks and swimmers need flexible shoulders for efficient strokes!

Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Muscles never work alone - they operate in antagonistic pairs where one muscle contracts while its partner relaxes. When you bend your elbow, your biceps acts as the agonist (the muscle doing the work) while your triceps becomes the antagonist (the relaxing muscle). These roles flip when you straighten your arm.
There are three types of muscle contractions you need to know. Isometric contractions happen when muscles contract without changing length - think planks or wall sits where you're holding position. Isotonic contractions involve muscle length changes during movement.
Isotonic concentric contractions shorten the muscle (like lifting weights up), while isotonic eccentric contractions lengthen the muscle under tension (like slowly lowering weights down). Eccentric contractions are crucial for controlling movement and preventing injury.
Real Example: During a bicep curl, lifting the weight uses concentric contraction, while slowly lowering it uses eccentric contraction - both are equally important for strength building!

Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Analysing sporting movements becomes straightforward once you understand the basics. During the drive phase of sprinting, your ankle performs plantar flexion (pointing toes) using the gastrocnemius, your knee extends via the quadriceps, and your hip extends through the powerful gluteus maximus - all using concentric contractions.
In javelin throwing, the preparation phase involves elbow extension (triceps working concentrically) and shoulder abduction (deltoid contracting). The pull-back phase of kicking shows your ankle in plantar flexion, knee flexing through hamstring contraction, and hip extending via the glutes.
Each movement analysis requires identifying the joint type , the specific movement occurring, which muscles are the agonist and antagonist, and what type of contraction is happening. This systematic approach works for any sporting action.
Exam Success: Practice analysing everyday movements like walking upstairs or throwing a ball - the more you apply these concepts, the easier they become to spot in exam questions!
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Quotes from every main character
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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