MadSci Network: Anatomy

Re: What keeps a human heart beating?

Date: Fri Oct 23 10:47:10 1998
Posted By: Terry Hebert, Faculty, Universite de Montreal, Biochemistry, Montréal Heart Institute
Area of science: Anatomy
ID: 907287484.An

The normal heart is a strong, muscular pump a little larger than a fist. It pumps blood continuously through the circulatory system. Each day the average heart "beats" (or expands and contracts) 100,000 times and pumps about 2,000 gallons of blood. In a 70-year lifetime, an average human heart beats more than 2.5 billion times. It never stops beating until it fails and the result is usually death if it is not restarted quickly.

The source of energy for the heart, like all other tissues is ATP or adenosine triphosphate. This high energy molecule is generated by the metabolism of food that you ingest. In the case of the heart, most of the energy at rest is generated by metabolism of fatty acids (approximately 70%) and some carbohydrates. ATP is produced either in the motochondria through a series of enzymatic steps or under certain conditions (when the heart is not getting enough oxygen, a condition called ischemia) by anaerobic glycolysis.

The second part of your question, is the heart electric? Well, in a sense it is because the beating of the heart is controlled by the generation of repeated electrical signals in two specialized regions of the heart called the sionatrial node and the atrial ventricular node. These signals are propagated through the heart in a well-controlled synchronized manner which you hear as the “lub-dup” of the pump (or contracting muscle) when you listen to your heartbeat. The synchronized contraction of all the chambers of your heart is critical for blood flow to be maintained for your body and brain. Thus, while electricity is not the fuel for your heart, it does in fact control its operation.

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