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Organisms respond to changes in their internal and external environments (a-level only)
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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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Biology
29 Nov 2025
1,040
1 page
Marisa Smith @marisasmith_qauu
Your nervous system is like a complex electrical network that helps you sense the world around you and... Show more
Ever wondered how you instantly pull your hand away from something hot? It all starts with sensory receptors - specialised nerve endings that act like biological sensors, detecting changes in your environment and converting them into electrical signals.
These receptors are incredibly specific. Your light-sensitive cells (rods and cones) in your retina only respond to light changes, whilst thermoreceptors in your skin and brain detect temperature shifts. Pacinian corpuscles sense pressure changes when something touches your skin. Think of them as biological transducers, changing one type of energy into electrical energy your brain can understand.
Neurones are the messenger cells that carry these electrical signals throughout your body. They've got a distinctive structure dendrites receive signals, the cell body processes them, and the axon transmits them onwards. Many axons are wrapped in a fatty myelin sheath with gaps called nodes of Ranvier - this setup massively speeds up signal transmission.
Key Point Each sensory receptor type is highly specific to one stimulus - you can't hear light or see sound because receptors only respond to their designated energy type.
The magic happens through nerve impulses - electrical signals that zip along neurones. At rest, the inside of a neurone sits at -60mV compared to the outside, maintained by the sodium-potassium pump constantly moving ions around. When stimulated enough to reach the threshold potential of -50mV, voltage-gated sodium channels burst open, causing depolarisation as the inside becomes positive . This triggers a cascade effect, with the signal racing along the axon as a wave of depolarisation.
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.
15
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the detailed processes of action potential generation and synaptic transmission in neurons. This study note covers the roles of ion channels, neurotransmitters like acetylcholine, and the sequence of events from depolarization to repolarization. Ideal for Edexcel A Level Biology students focusing on spec points 8-5 and 8-7.
BiologyExplore the essential concepts of carbohydrates, including definitions, classifications (monosaccharides, disaccharides, polysaccharides), and key reactions such as glycosidic bond formation. This summary covers important examples like glucose, maltose, and sucrose, along with tests for reducing and non-reducing sugars. Ideal for AQA A-level Biology students.
BiologyExplore the fundamental concepts of human cell biology, including cell division, DNA structure and replication, gene expression, and metabolic pathways. This comprehensive summary covers key topics such as mitosis, meiosis, mutations, and cellular respiration, providing essential insights for Higher Human Biology students. Ideal for exam preparation and understanding cellular processes.
BiologyExplore the structure and function of the Central Nervous System (CNS) and neurons. This summary covers the roles of sensory, motor, and relay neurons, as well as the mechanisms of neural transmission and synaptic communication. Ideal for students studying human biology and neuroscience.
BiologyExplore the structure and function of neurons, synapses, and reflex arcs in the nervous system. This summary covers key concepts such as neural transmission, types of neurons, and the role of the nervous system in homeostasis. Ideal for Edexcel Biology students preparing for exams.
BiologyExplore key concepts in neurobiology and immunology, including immune responses, synaptic transmission, the effects of recreational drugs like cocaine and cannabis, and models of memory. This comprehensive overview covers the human nervous system, biological defenses, and the role of neurotransmitters, providing essential knowledge for higher human biology studies.
BiologyApp 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
Marisa Smith
@marisasmith_qauu
Your nervous system is like a complex electrical network that helps you sense the world around you and respond accordingly. Understanding how sensory receptors detect stimuli and how neurones transmit these signals is crucial for grasping how your body coordinates... Show more
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Ever wondered how you instantly pull your hand away from something hot? It all starts with sensory receptors - specialised nerve endings that act like biological sensors, detecting changes in your environment and converting them into electrical signals.
These receptors are incredibly specific. Your light-sensitive cells (rods and cones) in your retina only respond to light changes, whilst thermoreceptors in your skin and brain detect temperature shifts. Pacinian corpuscles sense pressure changes when something touches your skin. Think of them as biological transducers, changing one type of energy into electrical energy your brain can understand.
Neurones are the messenger cells that carry these electrical signals throughout your body. They've got a distinctive structure: dendrites receive signals, the cell body processes them, and the axon transmits them onwards. Many axons are wrapped in a fatty myelin sheath with gaps called nodes of Ranvier - this setup massively speeds up signal transmission.
Key Point: Each sensory receptor type is highly specific to one stimulus - you can't hear light or see sound because receptors only respond to their designated energy type.
The magic happens through nerve impulses - electrical signals that zip along neurones. At rest, the inside of a neurone sits at -60mV compared to the outside, maintained by the sodium-potassium pump constantly moving ions around. When stimulated enough to reach the threshold potential of -50mV, voltage-gated sodium channels burst open, causing depolarisation as the inside becomes positive . This triggers a cascade effect, with the signal racing along the axon as a wave of depolarisation.
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.
15
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the detailed processes of action potential generation and synaptic transmission in neurons. This study note covers the roles of ion channels, neurotransmitters like acetylcholine, and the sequence of events from depolarization to repolarization. Ideal for Edexcel A Level Biology students focusing on spec points 8-5 and 8-7.
BiologyExplore the essential concepts of carbohydrates, including definitions, classifications (monosaccharides, disaccharides, polysaccharides), and key reactions such as glycosidic bond formation. This summary covers important examples like glucose, maltose, and sucrose, along with tests for reducing and non-reducing sugars. Ideal for AQA A-level Biology students.
BiologyExplore the fundamental concepts of human cell biology, including cell division, DNA structure and replication, gene expression, and metabolic pathways. This comprehensive summary covers key topics such as mitosis, meiosis, mutations, and cellular respiration, providing essential insights for Higher Human Biology students. Ideal for exam preparation and understanding cellular processes.
BiologyExplore the structure and function of the Central Nervous System (CNS) and neurons. This summary covers the roles of sensory, motor, and relay neurons, as well as the mechanisms of neural transmission and synaptic communication. Ideal for students studying human biology and neuroscience.
BiologyExplore the structure and function of neurons, synapses, and reflex arcs in the nervous system. This summary covers key concepts such as neural transmission, types of neurons, and the role of the nervous system in homeostasis. Ideal for Edexcel Biology students preparing for exams.
BiologyExplore key concepts in neurobiology and immunology, including immune responses, synaptic transmission, the effects of recreational drugs like cocaine and cannabis, and models of memory. This comprehensive overview covers the human nervous system, biological defenses, and the role of neurotransmitters, providing essential knowledge for higher human biology studies.
BiologyApp 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
Sociology