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The Nervous System and Neurones
Ever wondered how you pull your hand away from something hot before you even think about it? That's your nervous system in action, using specialised cells called neurones to send electrical messages around your body.
Neurones are basically biological electrical cables with three main jobs. Sensory neurones carry signals from your sense organs (like eyes and skin) to your central nervous system (CNS) - that's your brain and spinal cord. Motor neurones do the opposite, carrying messages from your CNS to muscles and glands called effectors. Relay neurones work as connectors inside your CNS, linking sensory and motor neurones together.
Each neurone has a cell body containing the nucleus and main organelles, plus long, thin fibres called axons that carry the electrical impulses. Many axons are wrapped in a fatty myelin sheath that acts like insulation on electrical wire - it speeds up the impulse and stops electrical energy from leaking out.
Quick Tip: Think of neurones like a relay race - sensory neurones detect the stimulus, relay neurones pass the message, and motor neurones make something happen!
The gaps between neurones are called synapses, where electrical impulses trigger the release of chemical messengers called neurotransmitters. These chemicals diffuse across the gap and trigger a new electrical impulse in the next neurone - it's like passing the baton in that relay race.
Reflex Arcs - Your Body's Emergency Response
Reflex arcs are your body's way of keeping you safe without waiting for your brain to think things through. When you touch something sharp, receptor cells detect this stimulus and fire an electrical impulse along a sensory neurone straight to your spinal cord - completely bypassing your brain for speed.
In your spinal cord, a relay neurone picks up the signal and passes it to a motor neurone, which rushes the message to your muscles. Your hand jerks away before you've even consciously felt the pain - that's an automatic response that could save you from serious injury.
This whole process happens in milliseconds because it's such an efficient system. The effectors (usually muscles) contract to move you away from danger, or sometimes glands release hormones if needed.
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Anna
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Thomas R
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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 Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
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Understanding the Nervous System: Edexcel Biology Notes
Your nervous system is like your body's electrical wiring, sending lightning-fast messages to keep you alive and responding to the world around you. Understanding how nerve cells work and communicate will help you grasp one of biology's most fascinating topics.
The Nervous System and Neurones
Ever wondered how you pull your hand away from something hot before you even think about it? That's your nervous system in action, using specialised cells called neurones to send electrical messages around your body.
Neurones are basically biological electrical cables with three main jobs. Sensory neurones carry signals from your sense organs (like eyes and skin) to your central nervous system (CNS) - that's your brain and spinal cord. Motor neurones do the opposite, carrying messages from your CNS to muscles and glands called effectors. Relay neurones work as connectors inside your CNS, linking sensory and motor neurones together.
Each neurone has a cell body containing the nucleus and main organelles, plus long, thin fibres called axons that carry the electrical impulses. Many axons are wrapped in a fatty myelin sheath that acts like insulation on electrical wire - it speeds up the impulse and stops electrical energy from leaking out.
Quick Tip: Think of neurones like a relay race - sensory neurones detect the stimulus, relay neurones pass the message, and motor neurones make something happen!
The gaps between neurones are called synapses, where electrical impulses trigger the release of chemical messengers called neurotransmitters. These chemicals diffuse across the gap and trigger a new electrical impulse in the next neurone - it's like passing the baton in that relay race.
Reflex Arcs - Your Body's Emergency Response
Reflex arcs are your body's way of keeping you safe without waiting for your brain to think things through. When you touch something sharp, receptor cells detect this stimulus and fire an electrical impulse along a sensory neurone straight to your spinal cord - completely bypassing your brain for speed.
In your spinal cord, a relay neurone picks up the signal and passes it to a motor neurone, which rushes the message to your muscles. Your hand jerks away before you've even consciously felt the pain - that's an automatic response that could save you from serious injury.
This whole process happens in milliseconds because it's such an efficient system. The effectors (usually muscles) contract to move you away from danger, or sometimes glands release hormones if needed.
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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
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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
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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
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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
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Elisha
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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
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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.
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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.
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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!
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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
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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
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Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. 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