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A heartbeat is a two-part pumping action that takes about a second. As blood collects in the upper chambers (the right and left atria), the heart's natural pacemaker (the SA node) sends out an electrical signal that causes the atria to contract.
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Mar 12, 2023 · The right atrium is one of four heart chambers and related valves, which include two atria at the top of the heart with two ventricles at the bottom. The cardiac electrical signal controls the heartbeat in two ways. First, since each electrical impulse generates one heartbeat, the number of electrical impulses determines the heart rate. In a ...
- Overview
- Anatomy of the heart
- How the heart works
- Valves
- The heart’s electrical system
- Blood vessels
- Cardiac arrest: When the heart stops
- Conclusion
The human heart is a finely-tuned instrument that serves the whole body. It is a muscular organ around the size of a closed fist, and it sits in the chest, slightly to the left of center.
The heart beats around 100,000 times a day, pumping approximately 8 pints of blood throughout the body 24/7. This delivers oxygen- and nutrient-rich blood to tissues and organs and carries away waste.
The heart sends deoxygenated blood to the lungs, where the blood loads up with oxygen and unloads carbon dioxide, a waste product of metabolism.
Together, the heart, blood, and blood vessels — arteries, capillaries, and veins — make up the circulatory system.
Below is an interactive 3D model of the heart. Explore the model using your mouse pad or touchscreen to learn more.
The heart consists of four chambers:
•The atria: These are the two upper chambers, which receive blood.
•The ventricles: These are the two lower chambers, which discharge blood.
A wall of tissue called the septum separates the left and right atria and the left and right ventricle. Valves separate the atria from the ventricles.
The heart’s walls consist of three layers of tissue:
The rate at which the heart contracts depends on many factors, such as:
•activity and exercise
•emotional factors
•some medical conditions
•a fever
•some medications
The heart has four valves to ensure that blood only flows in one direction:
•Aortic valve: This is between the left ventricle and the aorta.
•Mitral valve: This is between the left atrium and the left ventricle.
•Pulmonary valve: This is between the right ventricle and the pulmonary artery.
•Tricuspid valve: This is between the right atrium and right ventricle.
Most people are familiar with the sound of the heart. In fact, the heart makes many types of sound, and doctors can distinguish these to monitor the health of the heart.
To pump blood throughout the body, the muscles of the heart must work together to squeeze the blood in the right direction, at the right time, and with the right force. Electrical impulses coordinate this activity.
The electrical signal begins at the sino-atrial node, sometimes called the sinus, or SA, node. This is the heart’s pacemaker, and it sits at the top of the right atrium. The signal causes the atria to contract, pushing blood down into the ventricles.
The electrical impulse then travels to an area of cells at the bottom of the right atrium, between the atria and ventricles, called the atrioventricular, or AV, node.
These cells act as a gatekeeper. They coordinate the signal so that the atria and ventricles do not contract at the same time. There needs to be a slight delay.
There are three types of blood vessels:
Arteries: These carry oxygenated blood from the heart to the rest of the body. The arteries are strong, muscular, and stretchy, which helps push blood through the circulatory system, and they also help regulate blood pressure. The arteries branch into smaller vessels called arterioles.
Veins: These carry deoxygenated blood back to the heart, and they increase in size as they get closer to the heart. Veins have thinner walls than arteries.
Capillaries: These connect the smallest arteries to the smallest veins. They have very thin walls, which allow them to exchange compounds such as carbon dioxide, water, oxygen, waste, and nutrients with surrounding tissues.
The heart, blood, and blood vessels make up the circulatory, or cardiovascular, system.
Here, learn about some diseases that can affect this system.
The heart is essential to life — if it stops beating, blood will not reach the brain and other organs, and the person can die within minutes. This is called cardiac arrest.
If a person experiences cardiac arrest, they will be unable to speak or breathe, and they will have no heartbeat.
Anyone nearby should call 911 immediately and start cardiopulmonary resuscitation (CPR), pressing hard and fast with locked hands on the center of the person’s chest.
According to the Centers for Disease Control and Prevention (CDC), CPR can double or triple a person’s chance of survival after their heart stops.
The heart is an essential, powerful organ that constantly pumps oxygen and nutrients around the body.
If a person is born with congenital heart disease, or if damage occurs due to illness or other factors, the heart’s function may diminish, and this can lead to life threatening complications, such as heart failure.
Here, learn about preventing and treating different types of heart disease.
If the heart stops, a person cannot survive for long. Staying active and maintaining a healthful diet are two ways to protect the heart.
Learn about foods for a healthy heart here.
Read this article in Spanish.
Mar 24, 2022 · Your heart has a special electrical system called the cardiac conduction system. This system controls the rate and rhythm of the heartbeat. With each heartbeat, an electrical signal travels from the top of the heart to the bottom. As the signal travels, it causes the heart to contract and pump blood.
Your heart pumps blood through three types of blood vessels: Arteries carry oxygen-rich blood from your heart to your body’s tissues. The exception is your pulmonary arteries, which go to your lungs. Veins carry oxygen-poor blood back to your heart. Capillaries are small blood vessels where your body exchanges oxygen-rich and oxygen-poor blood.
The heart beats because of a small electrical current generated by the the cardiac conduction system. The cardiac conduction system is a group of muscle cells in the walls of the heart. It's comprised of five major components: The sinoatrial node (SA node): Known as the heart's "pacemaker", this node fires at regular intervals, causing the ...
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Oct 31, 2024 · The heart cavity is divided down the middle into a right and a left heart, which in turn are subdivided into two chambers. The upper chamber is called an atrium (or auricle), and the lower chamber is called a ventricle. The two atria act as receiving chambers for blood entering the heart; the more muscular ventricles pump the blood out of the ...
