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Rachel Bremner
18/11/2025
PE
The Cardiovascular System
165
•
18 Nov 2025
•
Understanding the Cardiovascular System: Blood Flow and Heart Functions
Rachel Bremner
@rachelbremner_qhci
The Cardiovascular System: Your Body's Transport Network
Think of your cardiovascular system as the ultimate delivery network - it's made up of your heart (the pump), blood vessels (the roads), and blood (the delivery trucks). This system ensures every cell in your body gets the oxygen and nutrients it needs whilst removing waste products like carbon dioxide.
Your heart is essentially a muscular pump with four main chambers - two atria (upper chambers) and two ventricles (lower chambers). The right side handles deoxygenated blood, whilst the left side deals with oxygenated blood. The septum acts like a wall, keeping these two sides completely separate.
Heart valves are like one-way doors that prevent blood from flowing backwards. The tricuspid valve (3 cusps) separates the right atrium and ventricle, whilst the bicuspid valve (2 cusps) does the same job on the left side. Semilunar valves control blood flow out of the ventricles into the major arteries.
Quick Tip: Remember "Tri-Right, Bi-Left" - tricuspid on the right, bicuspid on the left!
Blood Vessels: The Transport Routes
Arteries are the motorways of your circulatory system - they carry blood away from your heart at high speed and pressure. They have thick, elastic walls and small lumens (internal spaces) to cope with this pressure. Most arteries carry oxygenated blood, except the pulmonary artery which takes deoxygenated blood to your lungs.
Veins work like the return journey - they bring blood back to your heart. They have thin walls, large lumens, and operate under low pressure. Special valves prevent blood from flowing backwards. Most veins carry deoxygenated blood, except the pulmonary vein which returns oxygenated blood from your lungs.
Capillaries are where the magic happens - these tiny vessels have walls just one cell thick, allowing easy gas exchange. Blood cells move through them single file, ensuring maximum contact time for oxygen and nutrients to diffuse into your tissues.
Memory Trick: Arteries = Away from heart, Veins = Venture back IN to heart!
Blood Flow and Circulation
Your body operates a double circulatory system - your heart pumps blood to two destinations. Pulmonary circulation sends deoxygenated blood to your lungs for oxygenation, then back to your heart. Systemic circulation delivers oxygenated blood to your entire body, then returns deoxygenated blood to your heart.
The blood pathway follows a specific route: deoxygenated blood from your body enters the right atrium, passes through the tricuspid valve to the right ventricle, then gets pumped through the pulmonary artery to your lungs. After oxygenation, blood returns via the pulmonary vein to the left atrium, through the bicuspid valve to the left ventricle, then out through the aorta to your body.
Red blood cells contain haemoglobin, a protein that binds with oxygen to form oxyhaemoglobin. This is how your blood actually carries oxygen around your body - it's not just dissolved in the liquid part of blood.
Exam Focus: Make sure you can trace the complete blood pathway - it's a common exam question!
Heart Rate and Exercise
Cardiac output is the volume of blood your heart pumps per minute, calculated as Stroke Volume × Heart Rate. Your stroke volume is how much blood gets pumped out of your left ventricle with each beat, typically measured in millilitres per beat.
During exercise, your body uses the vascular shunt mechanism to redirect blood where it's needed most. Vasoconstriction narrows blood vessels to areas that aren't essential during exercise (like your digestive system), whilst vasodilation widens vessels to supply working muscles with more blood.
This redistribution system is brilliant - it means your body can prioritise oxygen delivery to your muscles when you're active, whilst reducing supply to less critical areas. Understanding this helps explain why you shouldn't eat a big meal before exercising!
Real-World Connection: This is why you feel sick if you exercise too soon after eating - your digestive system is competing with your muscles for blood supply!
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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
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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
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 the Cardiovascular System: Blood Flow and Heart Functions
Rachel Bremner
@rachelbremner_qhci
Your heart and blood vessels work like a delivery service, constantly transporting oxygen, nutrients, and waste around your body. Understanding how this cardiovascular system operates is crucial for GCSE PE, especially when learning about exercise and performance.
The Cardiovascular System: Your Body's Transport Network
Think of your cardiovascular system as the ultimate delivery network - it's made up of your heart (the pump), blood vessels (the roads), and blood (the delivery trucks). This system ensures every cell in your body gets the oxygen and nutrients it needs whilst removing waste products like carbon dioxide.
Your heart is essentially a muscular pump with four main chambers - two atria (upper chambers) and two ventricles (lower chambers). The right side handles deoxygenated blood, whilst the left side deals with oxygenated blood. The septum acts like a wall, keeping these two sides completely separate.
Heart valves are like one-way doors that prevent blood from flowing backwards. The tricuspid valve (3 cusps) separates the right atrium and ventricle, whilst the bicuspid valve (2 cusps) does the same job on the left side. Semilunar valves control blood flow out of the ventricles into the major arteries.
Quick Tip: Remember "Tri-Right, Bi-Left" - tricuspid on the right, bicuspid on the left!
Blood Vessels: The Transport Routes
Arteries are the motorways of your circulatory system - they carry blood away from your heart at high speed and pressure. They have thick, elastic walls and small lumens (internal spaces) to cope with this pressure. Most arteries carry oxygenated blood, except the pulmonary artery which takes deoxygenated blood to your lungs.
Veins work like the return journey - they bring blood back to your heart. They have thin walls, large lumens, and operate under low pressure. Special valves prevent blood from flowing backwards. Most veins carry deoxygenated blood, except the pulmonary vein which returns oxygenated blood from your lungs.
Capillaries are where the magic happens - these tiny vessels have walls just one cell thick, allowing easy gas exchange. Blood cells move through them single file, ensuring maximum contact time for oxygen and nutrients to diffuse into your tissues.
Memory Trick: Arteries = Away from heart, Veins = Venture back IN to heart!
Blood Flow and Circulation
Your body operates a double circulatory system - your heart pumps blood to two destinations. Pulmonary circulation sends deoxygenated blood to your lungs for oxygenation, then back to your heart. Systemic circulation delivers oxygenated blood to your entire body, then returns deoxygenated blood to your heart.
The blood pathway follows a specific route: deoxygenated blood from your body enters the right atrium, passes through the tricuspid valve to the right ventricle, then gets pumped through the pulmonary artery to your lungs. After oxygenation, blood returns via the pulmonary vein to the left atrium, through the bicuspid valve to the left ventricle, then out through the aorta to your body.
Red blood cells contain haemoglobin, a protein that binds with oxygen to form oxyhaemoglobin. This is how your blood actually carries oxygen around your body - it's not just dissolved in the liquid part of blood.
Exam Focus: Make sure you can trace the complete blood pathway - it's a common exam question!
Heart Rate and Exercise
Cardiac output is the volume of blood your heart pumps per minute, calculated as Stroke Volume × Heart Rate. Your stroke volume is how much blood gets pumped out of your left ventricle with each beat, typically measured in millilitres per beat.
During exercise, your body uses the vascular shunt mechanism to redirect blood where it's needed most. Vasoconstriction narrows blood vessels to areas that aren't essential during exercise (like your digestive system), whilst vasodilation widens vessels to supply working muscles with more blood.
This redistribution system is brilliant - it means your body can prioritise oxygen delivery to your muscles when you're active, whilst reducing supply to less critical areas. Understanding this helps explain why you shouldn't eat a big meal before exercising!
Real-World Connection: This is why you feel sick if you exercise too soon after eating - your digestive system is competing with your muscles for blood supply!
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?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
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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4.8/5
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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