Eli5: What create a heart beat?

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Can anyone explain this in more engineering terms? Biology can be difficult for me to read and to understand.

In: 2

basically, the heart pumps blood in and out by contracting and expanding. each time it does this it sort of tenses or relaxes the muscle rapidly, which is felt as the beat (in the chest). as the blood rapidly travels around the body through the veins, it can also be felt in certain spots like the neck and wrists.

TLDR it rapidly pushes the blood around the body in a regular contracting/expanding motion

There are few different ways to look at this.

In your chest the expansion and contraction of you heart opens and closes valves between chambers and blood vessels to pass blood through.

Your heart is a pump, when your heart contracts it pushes blood into your arteries through your body. This can be felt as a pulse in may spots including you neck (carotid), wrist (radial), bicep (brachial), groin (femoral), feet (pedal). Once the chamber it must expand to refill with blood.

You heart also creates an electrical pulse, which can be measured by an EKG, which is what causes the heart to expand and contract.

I guess there’s two answers:

1) the heart actually beats because of a group of cells called pacemaker cells. They create electrical impulses by moving electrically charged atoms in and out of their cell membrane, which in turn triggers the nerves and muscles in the heart to contract and pump the blood.

2) the heartbeat that you *hear* in the stethoscope is caused by the valves in your heart opening and closing. They are also triggered and timed by the pacemaker cells.

There’s a timed pulse generator (SA node) connected to 4 pumps (the heart chambers) via a way to delay the signal (AV node). 2 of these pumps (atria) empty into the other 2 (ventricles), which empty into general circulation (left side of the heart) and an oxygenation chamber (lungs). The delay is between the atria pumping and the ventricles pumping.

There are valves between each of these chambers and both circulations to prevent backflow of blood. The closing of these is what you hear and feel as a heartbeat.