HOW THE HEART WORKS
THE LONGEST LIST OF THE LONGEST
STUFF AT THE LONGEST DOMAIN NAME AT LONG LAST
How does the heart work?
This blood then goes to the lungs and fills itself with oxygen. It then travels
through the pulmonary veins back to the heart and enters the left atrium. As the
left atrium contracts, blood is pushed through the mitral valve and travels into
the left ventricle. Although all ventricles of the heart are important, the left
ventricle is the most important. This is because it takes the blood that it
receives and pushes it through the aorta, which is the main artery in the body.
This delivers the oxygen-rich blood back to the different parts of the body. The
left ventricle is the thickest part of the heart due to the amount of muscle
that it takes to push the blood throughout the body against a much higher
pressure in circulation.
The contracting and relaxing of the heart is due to the hearts electrical
system. The electrical system is comprised of a group of cells that have the
ability to create electrical activity on their own. This group of cells pull
charged particles apart and pushes them throughout the cells. This causes an
electrical current in the pacemaker cells and those cells distribute themselves
among the heart and that causes the heart to contract. The pacemaker cells do
this at a remarkable speed, every second of the day. It is these impulses that
cause the heart to contract.
The sinoatrial node is the term for the pacemaker in the heart. This node is
located in the right atrium. There are fibers within the heart that take the
electricity from the pacemaker and distribute it throughout the rest of the
heart. It takes a total of 0.4 seconds for the electricity to leave the
sinoatrial node and go to the left and right atria, making them contract. The
electricity then travels to the atrioventricular node and to the Bundle of His.
It then separates into two different branches: the right bundle branch and the
left bundle branch. From there, it moves quickly to the Purkinje fibers in the
right and left ventricles, causing them to contract at the same time.
Although any of the electrical components of the heart have the ability to be
the pacemaker, the sinoatrial node moves at a much faster rate. If the
sinoatrial node were to ever break down, another electrical component could
replace it as the pacemaker but the entire process would happen more slowly. The
pacemaker is responsible for producing the electrical currents that cause the
heart to beat, there are nerves that can affect how the pacemaker does so. These
nerves make up the autonomic nervous system, which is comprised of two parts:
the sympathetic nerves, which quicken the heart rate and increase the strength
of the contraction, and the parasympathetic nerves, which slow down the heart
rate and decrease the strength of the contraction.
The arteries in the heart need to be kept clean so that a heart attack does not
result. The two main coronary arteries are the left main coronary artery and the
right coronary artery. The left main coronary artery branches out into the left
anterior descending branch and the left circumflex arteries. Each of these
arteries takes blood to the different parts of the heart and the electrical
When one of these coronary arteries becomes blocked, that artery cannot deliver
blood to the heart that the heart needs to perform properly. This is why when
someone has heart disease, high activity levels and exertion will cause them to
tire quickly and feel chest pain. Once the artery has some blockage, this is
called angina and if the blockage becomes worse, it’s called unstable angina.
Once the artery is completely blocked, a heart attack will occur.
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