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Cardiac Muscle Function

Medha Godbole
The cardiac muscle is the reason why your heart beats. If this muscle ceases to function, a person is scientifically dead. Explore the wondrous functions of the cardiac muscle, as you keep reading.
The human body consists of a number of muscles. All these muscles come under three categories. The cardiac muscle being one, skeletal and smooth muscle being the other two. While the skeletal muscles stretch to various parts of the body like arms, legs, etc., smooth muscles are spotted in the stomach, artery and intestinal walls, veins and other organs.
Distinctive from these two, the cardiac muscle is found only in the heart. It is said to be a hybrid of the skeletal and smooth muscle. It is an involuntary muscle that contains striped and smooth tissues. It has Y-shaped cells that are shorter and wider compared to the cells of the skeletal muscle.

The cardiac muscle is located in the walls of the heart, precisely, in the myocardium. Activities of the cardiac muscle is highly controlled by the autonomic nervous system. Let us glance through the functions of this muscle, in detail.

Functions of the Cardiac Muscle

The Chief Function
The heart is mainly composed of cardiac muscle, hence, this muscle plays an important role in the functioning of the heart. Intercalated cells in this muscle help in the contraction of multiple cells. As mentioned, our heartbeats are an outcome of the constant contraction of the cardiac muscle.
As long as this muscle gets a sufficient supply of oxygen and nutrients, it will never cease its contracting process. The cells that cause this muscle to contract are called pacemaker cells.

No organism can stay alive without functioning of the cardiac muscle. The ventricles (a chamber of the heart) stretch beyond their resting capacity when they are filled.
They pump out the blood and carry it back to the heart. The cardiac muscle facilitates the pumping action of the ventricle. It squeezes blood out of your heart while contracting, and retrieves blood by relaxing.
It pumps the deoxygenated blood from the right atrium (a chamber of the heart) and right ventricle to the lungs, and pumps oxygenated blood through the left atrium and left ventricle to other parts of the body and the aorta.
The Cardiac Muscle fibers
Cardiac muscle fibers are striated and branched (Y-shaped). Each of them have a single central nuclei. Unlike smooth muscles that are linear, the cardiac muscle has a crisscross network of fibers. These fibers stretch in various directions.
They form a mesh enabling the cardiac muscle to squeeze the blood out of the heart for its supply to the lungs or the rest of the body, through the circulatory system. If by any chance, this mesh stops contracting, a person will suffer a cardiac arrest.
T-tubules, also known as transverse tubules, are pathways for electrical stimulation to reach and activate the muscle. There are very few transverse tubules in the cardiac muscle. Their feature of being large and broad in size, helps in facilitating better signal and activation of a muscle.
Although the cardiac muscle is constantly working by contracting and relaxing at least twice in a second, it never gets tired. It uses up oxygen to generate its energy called adenosine triphosphate. These muscle cells also break down glucose into pyruvate.
When the cardiac muscle has to work more or when there is lack of oxygen supply, it uses up the glucose in the bloodstream more than the free fatty acids. This happens mostly when we exert ourselves by exercise, etc. Whereas, when we stress over things, this muscle uses free fatty acids instead of glucose.
When the level of oxygen is low, the cardiac muscle becomes incapable of producing adenosine triphosphate. In such times, this muscle metabolizes anaerobically. The muscle completes this procedure by metabolizing glucose to lactic acid.
In this process, adenosine triphosphate is formed but, not as much as it is formed with oxygen. The cardiac muscle also stores energy in the form of creatine phosphate.
Electrical System of the Muscle
The cardiac muscle requires a special electrical system for sending the correct signals, at the appropriate time, to function properly. Electrical signals that lead to contraction, originate in the wall of the right atrium, where the heart's pacemaker (sinoatrial node) is.
A procrastination between the atria and ventricle muscles is required, in order to ensure that all the blood within the chamber is pumped out. This process is completed through the SA (sinoatrial node). The SA node directs electrical impulses to the right section of the heart at the right time.
To maintain conformable blood pressure and to prepare the heart for its next contraction, the SA node constantly prolongs a small amount of tension over all the muscles.
Cell Regeneration
In early times, it was believed that the cardiac cells do not regenerate. The cells that were lost in a heart attack, surgeries or other related damages, were said to be lost forever. Evidence was found in a scientific study in the year 2009, that after being created, cardiac cells further divide.
Hence, the study showed evidence of the regeneration of these cells. However, the rate at which they regenerate is still unknown.
The above information can be summed up with the fact that, survival is practically impossible without the cardiac muscle. This muscle is very important for any living organism, as it regulates the functions of the heart. Stay active and keep exercising to keep this muscle and your heart healthy.