[Biology Class Notes] on Myocardium Pdf for Exam

Muscles are the basic units of our skeletal system. The function of muscles is to contract and go back to shape. Most of the muscles occur in pairs so that their functioning is complementary to each other. When one muscle contracts, the other muscle relaxes. For that, these muscles need energy. These muscles utilize the ATP produced within their tissues with the help of oxygen. ‘Myo’ is a Greek-origin root word meaning muscles. Scientifically, muscles’ ability to contract is called my propulsion, or the tissues are called my propulsive tissues.

The origin of muscles is called myogenesis, and it occurs during embryonic development. The difference between muscle tissues and other tissues is in the presence of contractile protein in muscle tissues. These contractile proteins are called actin and myosin. These proteins contract and relax to cause the movement of muscles. There are other muscle proteins present in the muscles. These are regulatory proteins. These are tropomyosin and troponin.

Different Types of Muscles in Human

There are three types of muscles. Striated muscles (skeletal muscles), non-striated muscles (smooth muscles), and cardiac muscles (Myocardium). Skeletal muscles are connected to the bones and contribute to most parts of the body. The major movement of limbs is caused by the contraction and relaxation of skeletal muscles. Skeletal muscles are voluntary muscles that mean these are connected with the Central Nervous System. Other forms of muscles are smooth muscles. Smooth muscles are non-striated muscles, and these are involuntary muscles. These constitute the walls of organs and structures such as the urethra, uterus, bladder, blood vessels, oesophagus, stomach, intestine, bronchi, etc.

What is The Myocardium of Heart?

To answer the question of what is myocardium we can say that it is the involuntary muscles and striated muscles. This means we cannot control its function as it is controlled by ANS (Autonomous Nervous System).

Let us first understand the layers of the heart wall. The heart wall is constituted of three layers. Endocardium, myocardium, and pericardium. The inner wall is called the endocardium; the middle layer and outer layers are the myocardium and pericardium, respectively. The middle layer, the myocardium, is very thick, and it is supplied with blood via the coronary circulatory system. 

Functions of Myocardium

The cardiac muscles are joined together with intercalated discs. So, in brief, cardiac muscles consist of individual heart muscle cells, cardiomyocytes connected by intercalated discs to work a single unit. The cardiac muscle cells are covered with collagen fibers and other substances. These substances form the extracellular matrix. The cardiac muscles are not very different from skeletal muscle, although there are some little differences. Its functioning principle is electrical stimulation. Electrical stimulation, also called ‘cardiac action potential,’ stimulates and triggers the tissue to release calcium from the sarcoplasmic reticulum. 

The sarcoplasmic reticulum is the calcium store of muscle cells. When the concentration of calcium increases, it causes the myofilaments present in the myocardial cells to slide onto each other. This process is called excitation-contraction coupling. This is what myocardium of heart is, and this is how myocardium functions. There are no layers of the myocardium.

There are some diseases related to the myocardium. Ischemia, myocardial infarction, etc., are prominent among them. Ischemia is the reduction of blood flow to the heart muscles resulting in a lack of oxygen to the muscles. This is reversible, in which the tissues can be recovered once the blood flow resumes, or it can be irreversible, causing permanent death of tissues. There can be acute Ischemia, which is the sudden reduction of blood flow to the myocardium tissue. This is a stage which is called stunned myocardium. There also can be chronic Ischemia, in which the blood flow gets reduced slowly over some time. This stage of myocardium is called hibernating myocardium, where it looks like myocardium is hibernating and performing its work very slowly. This disease can be deadly.

The heart is a major part of our body. It is the heart of the body. So, it is imperative to take good care of our hearts. This discomfort sometimes feels like heartburn. There are other symptoms as well. These symptoms include shortness of breath, cold sweat, and feeling like fainting, nausea. The risk factors are if the person was smoking or diabetic, had high blood pressure, lacked exercise, obesity, the chances are a little higher.

The most common form of diagnosis is performing an ECG. In India, there is a general temperament of avoiding doctors unless it is very urgent. This should be discouraged. Everybody should check and take note of their Blood pressure from time to time and perform ECG from time to time and check the status of the heart when you pass fifty years of age. 

Most heart diseases show symptoms very late or have an immediate and devastating effect. so we should check-up from time to time so that heart diseases can be diagnosed before time.