Maths
Chemistry
Biology
English Language
History
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
Show all topics
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
Show all topics
Biology
13 Dec 2025
532
3 pages
Lucy @lucybennionx
Your nervous system is like your body's control centre, working alongside your senses to keep you alive and... Show more
Ever wondered how you can instantly recognise your mate across the school corridor? Your eye works like a sophisticated camera, with each part having a specific job. The cornea acts as your eye's front window, letting light in, while the iris controls how much light enters by adjusting the pupil size.
Inside your eye, the lens does the clever bit - it focuses light rays onto the retina, which contains millions of light-sensitive cells. These cells convert light into electrical signals that travel down the optic nerve straight to your brain. The ciliary body and suspensory ligaments work together to change the lens shape, helping you focus on objects at different distances.
Your brain processes all this visual information in different regions. The cerebrum handles your conscious thoughts, memory, and language, while the cerebellum keeps you balanced and coordinates muscle movement. The medulla controls unconscious activities like breathing, and the pituitary gland releases hormones that control your body's functions.
Quick Tip Remember that your eye and brain work as a team - damage to either can affect your vision and responses.
Think of homeostasis as your body's incredibly smart thermostat that keeps everything running perfectly. It maintains constant internal conditions like temperature, blood glucose, CO₂ levels, and water balance - essential for your cells to function properly.
When you're too hot, your body has two main cooling strategies. First, blood vessels vasodilate (widen) near your skin surface, allowing more blood to flow and lose heat through radiation. Second, you produce more sweat, which cools you down as the water evaporates and takes heat energy with it.
Feeling cold? Your body switches tactics completely. Blood vessels vasoconstrict (narrow) to reduce heat loss, and you produce less sweat to conserve water. If you're really cold, your muscles contract and relax rapidly, causing shivering - this movement requires energy from respiration, which produces heat as a byproduct.
Remember Homeostasis isn't just about temperature - it's your body's way of maintaining the perfect internal environment for survival.
Reflexes are your body's emergency response system - they're lightning-fast, automatic reactions that protect you from harm without any conscious thought. When you touch something hot, you don't think "I should move my hand" - you just do it instantly through a reflex arc.
The reflex pathway follows a simple route stimulus → receptor → sensory neurone → relay neurone (in CNS) → motor neurone → effector → response. This bypasses your brain's conscious decision-making, making it incredibly quick and potentially life-saving.
Communication between neurones happens at synapses - tiny gaps where neurones meet. Messages can't jump across these gaps, so your body uses chemical neurotransmitters instead. These chemicals travel across the gap and bind to receptor sites on the next neurone, continuing the message along.
For practical work, you'll often test reaction times using the ruler drop test. Your independent variables might include caffeine, alcohol, or distractions, while the dependent variable is the distance the ruler falls before you catch it.
Exam Focus Make sure you can draw and label a reflex arc - it's a common exam question worth easy marks!
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.
14
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the structure and function of the human nervous system, including the roles of the brain, spinal cord, and the three types of neurons: sensory, relay, and motor. This summary highlights neural transmission and the system's importance in responding to environmental changes and maintaining homeostasis.
BiologyExplore the intricate functions of the brain, nervous system, and endocrine system in maintaining homeostasis. This summary covers key concepts such as hormonal control, blood glucose regulation, and the structure of the eye, along with the mechanisms of synapses and reflex arcs. Ideal for students studying biology and human physiology.
BiologyExplore the structure and function of the Nervous System, including key concepts like neuronal communication, neuron types, synapses, and reflexes. This resource also covers required practical 8 on reaction time, detailing methods, variables, and essential definitions. Ideal for biology students seeking a comprehensive understanding of the human nervous system.
BiologyExplore the structure and function of the nervous system, including the central nervous system, neurons, synapses, and reflex arcs. This summary covers key concepts such as neural transmission and the roles of sensory and motor neurons in response mechanisms. Ideal for biology students seeking to grasp the essentials of human nervous system functionality.
BiologyExplore the structure and function of the nervous system, including the roles of neurons, the central and peripheral nervous systems, and their subdivisions. This summary covers key concepts such as neuron types, signal transmission, and the nervous system's role in communication within the body. Ideal for students studying biology or human anatomy.
BiologyExplore the mechanisms of hormonal and nervous control in the human body. This summary covers key concepts such as blood glucose regulation, the roles of insulin and glucagon, the structure and function of neurons, and the reflex arc. Understand how the endocrine and nervous systems work together to maintain homeostasis and respond to stimuli. Ideal for biology students preparing for exams.
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
Lucy
@lucybennionx
Your nervous system is like your body's control centre, working alongside your senses to keep you alive and functioning. Understanding how your eyes and brain work together, plus how your body maintains perfect internal conditions, is essential for GCSE Biology... Show more
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Ever wondered how you can instantly recognise your mate across the school corridor? Your eye works like a sophisticated camera, with each part having a specific job. The cornea acts as your eye's front window, letting light in, while the iris controls how much light enters by adjusting the pupil size.
Inside your eye, the lens does the clever bit - it focuses light rays onto the retina, which contains millions of light-sensitive cells. These cells convert light into electrical signals that travel down the optic nerve straight to your brain. The ciliary body and suspensory ligaments work together to change the lens shape, helping you focus on objects at different distances.
Your brain processes all this visual information in different regions. The cerebrum handles your conscious thoughts, memory, and language, while the cerebellum keeps you balanced and coordinates muscle movement. The medulla controls unconscious activities like breathing, and the pituitary gland releases hormones that control your body's functions.
Quick Tip: Remember that your eye and brain work as a team - damage to either can affect your vision and responses.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Think of homeostasis as your body's incredibly smart thermostat that keeps everything running perfectly. It maintains constant internal conditions like temperature, blood glucose, CO₂ levels, and water balance - essential for your cells to function properly.
When you're too hot, your body has two main cooling strategies. First, blood vessels vasodilate (widen) near your skin surface, allowing more blood to flow and lose heat through radiation. Second, you produce more sweat, which cools you down as the water evaporates and takes heat energy with it.
Feeling cold? Your body switches tactics completely. Blood vessels vasoconstrict (narrow) to reduce heat loss, and you produce less sweat to conserve water. If you're really cold, your muscles contract and relax rapidly, causing shivering - this movement requires energy from respiration, which produces heat as a byproduct.
Remember: Homeostasis isn't just about temperature - it's your body's way of maintaining the perfect internal environment for survival.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Reflexes are your body's emergency response system - they're lightning-fast, automatic reactions that protect you from harm without any conscious thought. When you touch something hot, you don't think "I should move my hand" - you just do it instantly through a reflex arc.
The reflex pathway follows a simple route: stimulus → receptor → sensory neurone → relay neurone (in CNS) → motor neurone → effector → response. This bypasses your brain's conscious decision-making, making it incredibly quick and potentially life-saving.
Communication between neurones happens at synapses - tiny gaps where neurones meet. Messages can't jump across these gaps, so your body uses chemical neurotransmitters instead. These chemicals travel across the gap and bind to receptor sites on the next neurone, continuing the message along.
For practical work, you'll often test reaction times using the ruler drop test. Your independent variables might include caffeine, alcohol, or distractions, while the dependent variable is the distance the ruler falls before you catch it.
Exam Focus: Make sure you can draw and label a reflex arc - it's a common exam question worth easy marks!
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.
14
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the structure and function of the human nervous system, including the roles of the brain, spinal cord, and the three types of neurons: sensory, relay, and motor. This summary highlights neural transmission and the system's importance in responding to environmental changes and maintaining homeostasis.
BiologyExplore the intricate functions of the brain, nervous system, and endocrine system in maintaining homeostasis. This summary covers key concepts such as hormonal control, blood glucose regulation, and the structure of the eye, along with the mechanisms of synapses and reflex arcs. Ideal for students studying biology and human physiology.
BiologyExplore the structure and function of the Nervous System, including key concepts like neuronal communication, neuron types, synapses, and reflexes. This resource also covers required practical 8 on reaction time, detailing methods, variables, and essential definitions. Ideal for biology students seeking a comprehensive understanding of the human nervous system.
BiologyExplore the structure and function of the nervous system, including the central nervous system, neurons, synapses, and reflex arcs. This summary covers key concepts such as neural transmission and the roles of sensory and motor neurons in response mechanisms. Ideal for biology students seeking to grasp the essentials of human nervous system functionality.
BiologyExplore the structure and function of the nervous system, including the roles of neurons, the central and peripheral nervous systems, and their subdivisions. This summary covers key concepts such as neuron types, signal transmission, and the nervous system's role in communication within the body. Ideal for students studying biology or human anatomy.
BiologyExplore the mechanisms of hormonal and nervous control in the human body. This summary covers key concepts such as blood glucose regulation, the roles of insulin and glucagon, the structure and function of neurons, and the reflex arc. Understand how the endocrine and nervous systems work together to maintain homeostasis and respond to stimuli. Ideal for biology students preparing for exams.
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