The heart is one of our strongest and most important muscles. It is the reason our other muscles have nutrients. Without the pumping action of the heart, we could not function. Knowledge of basic anatomy and circulation will help with understanding the characteristics of heartbeats themselves.
Anatomy
The heart is often the size of an adult's fist. It is a hollow organ made of a special muscle called myocardium. There are four chambers with in the heart. A septum in the middle divides the right from the left side; valves divide the top from the bottom. The top chamber is called an atrium and the bottom chamber is called a ventricle. There are four valves in the heart. The valves on the right side of the heart are the tricuspid, separating the atrium from the ventricle, and the pulmonary valve, separating the ventricle from the pulmonary artery. The left side has the mitral valve separating the atrium from the ventricle, while the aortic valve separates the ventricle from the the aorta.
Circulation
The veins carry de-oxygenated blood from the body to the right atrium, then to the right ventricle and eventually to the lungs. The lungs exchange the carbon dioxide in the blood for oxygen and move the newly oxygenated blood to the left atrium and then into the left ventricle. The left ventricle then pumps the blood through the arteries into the body. The different pumping actions of the chambers, as well as the valves between the chambers, are what make the beat of the heartbeat.
Beat
The top part of the atrium and the ventricles beat/contract at different times, determined by an electrical signal. The combination of the contraction along with closing of the valves, keeps the blood moving in one direction only. When listening or feeling for a heartbeat, the normal "lub-dub" sound is produced when the different valves slam shut. The atria beat together, and after a short pause, the ventricles beat together. The "lub" sound is produced by the closure of the tricuspid and mitral valves. The "dub" sound is produced with the closing of the pulmonary and aortic valves. Each "lub-dub" is counted as one full cycle of a heartbeat. The number of times the heart beats in one minute is the heart rate. The American Academy of Orthopedic Surgeons (AAOS) states that a heartbeat for a normal healthy adult will range from 60 to 100 beats per minute at rest. During activity, the heart can get up to 180 beats per minute. The cycle of the heart rate is measured in one-minute increments, for that is how long it takes the heart to pump our whole volume of blood through it.
Irregular Characteristics
Different sounds can be heard if the valves stop closing at the same time, or if they do not close completely. This is called an arrhythmia. There are four main types of arrhythmia, according to the National Institutes of Health. The most common arrhythmia is an extra beat or, more correctly, a premature beat. Other irregular heartbeats are caused by unequal timing between the atria and valves. There are even arrhythmias caused by the heart's electrical system not functioning properly. All of these irregularities need to be evaluated and monitored by a specialist, since they can lead to serious problems like heart failure or stroke.
References
- American Heart Association: heart anatomy
- NIH.gov: heart arrhythmia
- "AAOS Emergency Care and Transportation of the Sick and Injured;" American Academy of Orthopedic Surgeons; 2005
