Cardiac Muscle Function

The job our heart does is no mean feat. Thanks to our constant requirement of oxygen, it never gets to rest! But jokes apart, on a serious note, the fact that the human heart functions properly is a reason of us being alive. Our heart, as we all know is composed of chambers, two atria and two ventricles. The atria act as receiving chambers and the ventricles pump out the blood. Now, this 'pumping' action is facilitated by the cardiac muscle. It is one of the three major types of muscles, including the skeletal and smooth muscles. The contraction of the cells of this muscle in the heart push the blood from the atria and the ventricles till the circulatory system's blood vessels. The cells are like any other, depending on adequate blood supply for supplying oxygen and nutrients and removal of waste products.

Cardiac Muscle

Location: It is fundamentally an involuntary muscle and is located in the walls of the heart. To be precise, it is located in the myocardium. The myocardium is the layer of the heart between the other two layers, visceral and endocardium. All these three layers are packed with blood vessels.

Function: This muscle functions with the help of its cardiac cells. These cells are responsible for the contraction and sending blood to the atria and ventricles. That in turn, reaches the blood vessels of the circulatory system.

Cardiac Muscle Fibers: This muscle is not linear, unlike the striated or smooth muscles. It forms instead, a complicated and crisscross network of fibers, in any direction possible. The reason is that it performs the action of squeezing, what is called a bulb. Take an example of a water balloon being applied pressure on by a belt in a single direction. What will happen? Well, some amount of water will still be retained by the balloon. On the contrary, if you squeeze the balloon in all directions, there will be no water left in the balloon. Similarly, the fibers comprise a mesh, squeezing the chambers of the heart, forcing the blood either in lungs or through the entire body.

Metabolism: Believe it or not, our cardiac muscle does not ever get tired! Imagine the amount of pressure we put on it, it still goes on working, unfettered. The secret to it not being tired lies in the mitochondria. The mitochondria act as fuel plants for the cardiac cells. They generate adenosine triphosphate or ATP, a major source of chemical energy. Furthermore, lactate is converted into fuel by the muscle. This implies that even if the rest of the body is starved, the heart will always have fuel!

T-Tubules: Interestingly, there are pathways for electrical stimulation to reach and activate the muscle. These are called transverse tubules and even though there are fewer of these, they are broader and larger. This facilitates better signal and activation of the muscle.

Electro Chemical System of the Muscle: If the heart has to function properly, the cardiac muscle needs a special electrical system for sending the correct signals at the appropriate time. This then means that without a delay between the atrium and the ventricles for ensuring that all the blood is pumped out of the heart, it cannot happen. To facilitate this, the heart has sinoatrial node (SA node) for directing the electrical impulses to the right area of the heart at the right time. In addition to this, the SA node also maintains a tension on the muscles all the time. This helps in maintaining of blood pressure and keeps it ready for the next contraction.

The functioning is attributed to the cells in the muscle. Interestingly, these cells were believed not to regenerate and a heart attack or a surgery was supposed to damage these cells. But now it has been proved that these cells are capable of regeneration. I sign off here!