What is the Cardiac Muscle?

Niki Foster
Niki Foster

The cardiac muscle is the heart, responsible for pumping blood throughout the body. It is made up of cardiac muscle and is the only place in the body where such muscle is found. All the other muscles in the body are composed of either skeletal muscle or smooth muscle. The most muscular part of the heart is its middle layer, called the myocardium, which is mainly responsible for its contractions.

The heart is also known as the cardiac muscle.
The heart is also known as the cardiac muscle.

Cardiac muscle is unique because it is striated, like skeletal muscle, yet involuntary, like smooth muscle. Skeletal muscle controls the body's movement and is generally under conscious, or voluntary, control. The internal organs, on the other hand, with the exception of the heart, are made of smooth muscle, which works without conscious effort.

The anatomy of a heart attack.
The anatomy of a heart attack.

Striated muscle is arranged in protein filaments known as sarcomeres that are responsible for muscular contraction. Sarcomeres give muscles a striated, or striped, appearance. The striations in the cardiac muscle, unlike those in skeletal muscles, are branched, creating a more tenacious structure.

The cardiac muscle is very strong and resistant to fatigue, as it must work constantly throughout an organism's life. The average human heart contracts 70 times per minute to circulate blood through the body's blood vessels. The action potential, the electrochemical wave, responsible for the heartbeat comes from within the cardiac muscle itself, allowing the heart to continue to function even if the nerves enervating it are severed, as in the case of a heart transplant. The cardiac muscle is supplied by nerves, but the nervous system merely helps regulate the speed and strength of its contractions.

Unlike other muscles, cardiac muscle is nearly completely reliant on oxygen to function. While skeletal muscles can function anaerobically, using stored glycogen as a fuel source, the heart cannot to any significant degree. Therefore, damage and even death can occur very quickly whenever oxygen supply to the heart is blocked, such as during a heart attack.

On average, the human heart contracts about 70 times per minute.
On average, the human heart contracts about 70 times per minute.
Niki Foster
Niki Foster

In addition to her role as a wiseGEEK editor, Niki enjoys educating herself about interesting and unusual topics in order to get ideas for her own articles. She is a graduate of UCLA, where she majored in Linguistics and Anthropology.

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Discussion Comments


What is the waste product of the cardiac muscle?


It is located in the heart.


Where can the Cardiac muscle be found?


If you have high blood pressure for an extended period of time, you can stress your cardiac muscle out to the point of heart attack. It is strong and resistant to tiring out, but it can only take so much.

This is why doctors always insist that people with high blood pressure find a way to lower it. They either recommend losing weight, getting out of a stressful situation, or taking blood pressure medication.

I have high blood pressure, but since mine is caused by a kidney disease that restricts blood flow, my only option was medication. I take two kinds of blood pressure pills now, and I likely will have to continue taking them for the rest of my life. I don't mind, though, because I know that they are preserving the life of my heart.


@OeKc05 – Usually, someone will inject the heart with something to make it stop beating, and they will put it on ice until it gets where it needs to be. It can survive on ice for a few hours, so if it has to be flown to another hospital, it will still have a good chance of working.

However, I recently read an article about a new method that lets the heart keep beating from the time it is removed until the time it is implanted. They have come up with a box that will pump blood through the heart continuously, making it feel right at home.

Experts seem to think that this will keep the heart healthier in transit and provide better outcomes. I have a condition that will likely cause me to need a heart transplant someday, and I hope they have the method perfected by then.


I have seen a video of a heart being taken from a brain-dead patient before. It was pretty creepy how the heart kept beating after it was taken from the donor.

I wonder if it keeps beating because it can get oxygen from the surrounding air? Do surgeons implant it while it is still beating, or does it stop and have to be restarted? It looks like it would have a better chance of working in its new body if it had been steadily beating during the whole process.


@boathugger: It’s called action potential. The contractions of the cardiac muscle are triggered in a different way than the contraction of the skeletal muscle, which is caused by electrical impulses from nerve terminals located at the individual muscle fibers.

The heart cells do not have nerve terminals attached to them. To compensate for not having the nerve terminals, the heart cells have their own type of stimulus. They communicate directly with each other by passing electrical impulses to the neighbor cells. This enables the heart to be stimulated at just one location, with the electrical impulses passing on to the rest of the heart muscle which causes it to contract.


What exactly makes the cardiac muscle contract?

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