At British Heart Foundation, we talk a lot about hearts. It’s literally in our name. By volunteering at BHF, you help to raise vital lifesaving funds for research into heart and circulatory diseases. But do you understand what our hearts do, and how they work? If the answer is ‘no’, then don’t worry we’ve stripped things back to basics in this short easy-to-understand science lesson so you can learn why our hearts are so precious.
So, what actually is a heart?
If you're reading this, it means you're alive. You have a muscle, about the size of your fist, in the middle of your chest slightly tilted to the left.
Each day, this muscle - your heart - beats around 100,000 times, continuously pumping about five litres (eight pints) of blood around your body through a network of blood vessels called your circulatory system.
Your blood delivers oxygen and nutrients to all parts of your body to help your organs and muscles work properly. It also carries away unwanted carbon dioxide and waste products.
What does your heart look like?
Your heart has a left and a right side separated by a thin wall called the septum. Both sides have an upper and a lower chamber, called the left and right atrium and the left and right ventricle, respectively.
• The right atrium receives the low-oxygen blood that has just travelled round the body. The right atrium pumps the blood to the right ventricle.
• The right ventricle pumps the low-oxygen blood to the lungs to pick up a fresh supply of oxygen.
• The left atrium receives the high-oxygen blood from the lungs and pumps it to the left ventricle.
• The left ventricle pumps the high-oxygen blood to the rest of the body.
Your blood flows around your heart and the rest of your body in one direction, like a one-way traffic system. It is the heart valves that control the direction of the blood flow – they act like doors that open and close with every heartbeat.
Your heart is linked to the rest of the circulatory system with blood vessels called arteries and veins. Arteries deliver oxygen-rich blood from the heart to other areas of your body. Veins return the de-oxygenated blood from your organs back to your heart.
What does the heart's electrical system do?
Your heart's electrical system tells your heart when to contract and when to relax to keep your blood pumping regularly. The instructions to contract and relax are carried by electrical signals.
The electrical signals are sent from the sinus node which is known as your heart's natural pacemaker. Usually, the sinus node will send the electrical signals at a steady pace, but the pace can change depending on your emotions and if you are active or resting – this is your heart rate.
Exercise your heart to change your heart rate
If it’s safe for you to do so, try this short activity below to show how exercise affects your heart rate:
• Put two fingers (not your thumb, which has its own strong pulse) on the underside of your wrist. Can you find your pulse?
• Count the number of heartbeats you feel for 30 seconds. Write that number down and multiply it by two. That's your resting heart rate: the number of times your heart beats every minute when you are not moving much.
• Now, get ready to get moving! Do 25x star jumps, also known as jumping jacks (or as many as it takes to get out of breath). Not sure how to do a star jump? You can find this out on our website here.
•Without resting, count the number of heartbeats you feel in 30 seconds. Write that number down and multiply it by two. How much did your heart rate increase after the star jumps?
How did that feel? Did it make you feel alive? Find out more about your heart rate here.