How the heart beats
UPDATED: 15 December 2025
The Heart
Your heart is a vitally important pump located in your chest that beats every second of every day, pumping blood around your body. Since you only have one heart, you need to take care of it as best you can.
Its design is incredibly complex with many different parts, some moving, some muscular, and some electrical – let’s try to simplify these elements and give an overview of your heart’s structure and function.
A normal heart is made up of four rooms or chambers, each of which has a specific role.
The top chambers are called the Right Atrium and Left Atrium; these collect the blood returning from the body and lungs, respectively.
The bottom chambers are called the Right Ventricle and Left Ventricle; these are the two pumping chambers, pumping blood to the lungs (blood to be topped up with oxygen) and around the body, respectively.
Separating the heart chambers are valves made of tough, flexible tissue that open and close in response to pressure changes within the heart chambers. These are the doors controlling the smooth flow of blood through your heart, ensuring it is working as efficiently as possible.
The heart has its own blood supply delivered by the coronary arteries. They branch off from the main aorta and wrap around the heart supplying all heart tissue and muscle.
Heart anatomy
Muscle contraction
The Left Ventricle is usually the largest and most muscular heart chamber as its primary function is to pump blood (freshly topped up with oxygen by the lungs) out of the heart and around your body, delivering oxygen and nutrients to your brain, organs, muscles, and tissue.
During each heartbeat, the Left Ventricle contracts and squeezes, forcing blood out of the heart into and along blood vessels called arteries. You need some pressure to keep your blood moving.
Generates blood pressure
The volume of blood being forced out of your Left Ventricle generates an increased pressure within the arteries, which reaches a peak pressure called Systolic Blood Pressure.
Soon, the Left Ventricle finishes contracting and starts to relax again. As the muscular walls relax, the Left Ventricle refills with blood from the Left Atrium, getting ready for the next contraction.
This causes the blood pressure in the arteries to drop to its resting level, called Diastolic Blood Pressure.
The pressure wave of blood travelling along the inside of the arteries is the pulse you can feel when you check to see how fast your heart is beating.
Very little would happen in your body without a small bit of electricity. This is especially true of most muscles in the human body. Before they contract, they need a small electrical impulse to trigger them to contract. Since your heart is a muscular pump, every heartbeat is immediately preceded by a small electrical impulse that travels through the heart via a network of nerves called the Cardiac Conduction System.
Each electrical impulse starts high up in the Left Atrium and spreads across the two top heart chambers (the Atria) before reaching a mid-point between the top and bottom chambers.
Here, there is a short delay as the electrical impulse can only travel along one nerve fibre from the atria to the ventricles. Once through, the electrical impulse travels lightning fast along nerve fibres within the muscular walls of the ventricles, causing these chambers to contract.
After a short recharge time, another electrical impulse starts following the same pathway.
Electrical stimulation
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