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Cardiac muscle, also called myocardium, is one of three major categories of muscles found within the human body, the other two being smooth muscle and skeletal muscle. It is a specialised type of tissue that exists only in the heart. The heart is made up of three layers—pericardium, myocardium, and endocardium. The cardiac muscle is responsible for the contractility of the heart and, therefore, the pumping action. The primary function of the cardiac muscle is to pump blood into circulation by generating sufficient force. The cardiac muscle contracts and releases involuntarily, keeping the heart pumping and blood circulating throughout the body.
| Characteristics | Values |
|---|---|
| Types | Cardiac muscle is one of the three major categories of muscles found in the human body, the other two being smooth muscle and skeletal muscle. |
| Location | Cardiac muscle is found only in the heart. |
| Contractibility | Cardiac muscle contracts and releases involuntarily to keep the heart pumping blood around the body. |
| Structure | Cardiac muscle is made up of sarcomeres, which are contractile units that allow for contractibility. |
| Rhythm | The rhythmic contractions of the cardiac muscle are regulated by the sinoatrial node of the heart and are not under voluntary control. |
| Cells | Cardiac muscle cells are striated, branched, and contain many mitochondria. |
| Nucleus | Each cardiac muscle cell contains a single, centrally located nucleus surrounded by a cell membrane called the sarcolemma. Some cells may contain two nuclei. |
| Calcium | Calcium is involved in the process of excitation-contraction coupling, which causes the cell's myofilaments to slide past each other. |
| Electrical impulses | Electrical impulses from the nervous system cause the cardiac muscle cells to contract and expand. |
| Pacemaker cells | Cardiac muscle contains specialized "pacemaker" cells that set the rhythm of the heart contractions. |
| T-tubules | T-tubules are involved in transmitting electrical impulses and regulating calcium concentration within the cell. |
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What You'll Learn
- Cardiac muscle is one of three types of vertebrate muscle tissues
- The heart is made up of three layers—pericardium, myocardium, and endocardium
- Cardiac muscle cells are found only in the heart
- Cardiac muscle cells are involuntary and intrinsically controlled
- Diseases of the heart muscle are known as cardiomyopathies
Cardiac muscle is one of three types of vertebrate muscle tissues
Cardiac muscle, also known as myocardium, is one of three types of vertebrate muscle tissues, the other two being skeletal muscle and smooth muscle. It forms the thick middle layer of the heart, between the outer layer of the heart wall (the pericardium) and the inner layer (the endocardium). The heart is made up of these three layers, with the myocardium constituting the main tissue of the heart wall.
Cardiac muscle is a specialised, organised type of tissue that exists only in the heart. It is responsible for the contractility of the heart, allowing it to pump blood into circulation. The primary function of the individual cardiac muscle cells, or cardiomyocytes, is to contract and release involuntarily, keeping the heart pumping and blood circulating throughout the body. These cardiac cells work together to produce the rhythmic, wave-like contractions known as the heartbeat. The contractile functions of the heart require ATP, which can be obtained from various substrates, including fatty acids, carbohydrates, proteins, and ketones.
Cardiac muscle cells are shorter than skeletal muscle cells and form a network of many branches between the cells. They are also distinct from skeletal muscle cells in that they are intrinsically controlled and involuntary, meaning they are controlled unconsciously by regions of the brain stem and hypothalamus. Additionally, cardiac muscle cells contain a single nucleus, while skeletal muscle cells are multinucleated.
Cardiac muscle cells contain myofibrils, which are composed of repeating sections of sarcomeres. The sarcomeres consist of long proteins that organise into thick and thin filaments, or myofilaments. These myofilaments slide past each other during muscle contraction and relaxation, forming "cross-bridges" that cause the contraction of the heart and the generation of force. This process is activated by the release of calcium from the sarcoplasmic reticulum, which is triggered by electrical stimulation in the form of a cardiac action potential.
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The heart is made up of three layers—pericardium, myocardium, and endocardium
The heart is a muscular organ that pumps blood throughout the body. It is housed in a protective, fluid-filled sac called the pericardium. The heart itself is made up of three layers of tissue: the pericardium, myocardium, and endocardium.
The pericardium is a fibrous sac that surrounds the heart. It consists of the epicardium, pericardial space, parietal pericardium, and fibrous pericardium. The epicardium is the outermost layer of the heart and is also known as the visceral pericardium as it forms the inner layer of the pericardium. It is composed of loose connective tissue, including elastic fibres and adipose tissue. The epicardium helps to protect the inner heart layers and reduce friction.
The myocardium is the thickest layer of the heart, with its thickness varying in different parts of the heart. It is a muscular middle layer that enables the heart to contract and pump blood. Histologically, the myocardium is primarily composed of cardiac muscle cells (cardiomyocytes). Cardiomyocytes have a single nucleus in the centre of the cell, which helps to distinguish them from skeletal muscle cells that have multiple nuclei.
The endocardium is the innermost layer of the heart. It lines the inner surfaces of the heart chambers, including the heart valves. It is composed of simple squamous epithelial cells and forms the inner lining of the heart chambers and valves. The endocardium provides a smooth surface for efficient blood flow inside the heart chambers and houses capillaries to supply blood to the heart muscles.
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Cardiac muscle cells are found only in the heart
The human body contains three kinds of muscle tissue: skeletal, smooth, and cardiac. Cardiac muscle tissue, or myocardium, is a type of muscle tissue that forms the heart. It is responsible for keeping the heart pumping and blood circulating around the body.
Cardiac muscle is a specialized, organized type of tissue that exists only in the heart. It is made up of cardiac muscle cells, also called cardiomyocytes, which are tubular structures composed of chains of myofibrils. These myofibrils consist of repeating sections of sarcomeres, which are the fundamental contractile units of the muscle cells. The sarcomeres are composed of long proteins that organize into thick and thin filaments, called myofilaments. The myofilaments slide past each other as the muscle contracts and relaxes, causing the contraction of the heart and the generation of force.
Cardiac muscle cells are shorter than skeletal muscle cells and form a network of many branches between the cells. They are also involuntary and intrinsically controlled, meaning they are controlled unconsciously by regions of the brain stem and hypothalamus. The normal cardiac rhythm is set by specialized pacemaker cardiac muscle cells in the heart itself. These pacemaker cells generate electrical impulses, or action potentials, that tell cardiac muscle cells to contract and relax.
The heart wall is a three-layered structure with a thick layer of myocardium sandwiched between the inner endocardium and the outer epicardium. The cardiac muscle forms the thick middle layer of the heart and is responsible for the contractility of the heart, or the pumping action. The cardiac muscle must contract with enough force and blood to supply the metabolic demands of the entire body.
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Cardiac muscle cells are involuntary and intrinsically controlled
The human body contains three kinds of muscle tissue: skeletal, smooth, and cardiac. Cardiac muscle tissue, or myocardium, is a type of muscle tissue that forms the heart. It is responsible for keeping the heart pumping and blood circulating around the body.
Cardiac muscle is also considered to be an intrinsic or self-controlled tissue because the normal cardiac rhythm is set by specialized pacemaker cardiac muscle cells in the heart itself. These pacemaker cells are located in the sinoatrial node (the primary pacemaker) and the atrioventricular node (secondary pacemaker). They carry the impulses that are responsible for the beating of the heart.
Cardiac muscle cells are also characterized as striated, branched, and single nucleated. They are shorter than skeletal muscle tissue cells and form a network of many branches between the cells. The presence of myofibrils and many mitochondria in cardiac muscle cells provides them with great strength and endurance to pump blood throughout a lifetime.
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Diseases of the heart muscle are known as cardiomyopathies
Cardiac muscle, also known as myocardium, is one of three major categories of muscles in the human body, the other two being smooth muscle and skeletal muscle. The myocardium makes up the thick middle layer of the heart. The heart is made up of three layers: the pericardium, myocardium, and endocardium. The endocardium is not cardiac muscle and is comprised of simple squamous epithelial cells and forms the inner lining of the heart chambers and valves.
Cardiac muscle tissue is a specialized, organized type of tissue that exists only in the heart. It is responsible for keeping the heart pumping and blood circulating around the body. Unlike skeletal muscle, cardiac muscle tissue produces involuntary movements, meaning they are automatic and a person cannot control them. The heart also contains specialized types of cardiac tissue containing "pacemaker" cells that generate electrical impulses, or action potentials, that tell cardiac muscle cells to contract and relax.
There are different types of cardiomyopathies, including acquired and inherited forms. Acquired cardiomyopathy develops due to another disease, condition, or factor, such as coronary artery disease, autoimmune diseases, infections, heart inflammation, thyroid disease, muscular dystrophy, high cholesterol, sarcoidosis, amyloidosis, or hemochromatosis. Inherited cardiomyopathy, on the other hand, occurs when the gene for the disease is passed on from a parent. Genetic mutations can cause conditions such as hypertrophic cardiomyopathy (HCM), where the cardiomyocytes do not have a typical formation, leading to possible interruptions in blood flow out of the ventricles and causing arrhythmias or congestive heart failure.
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Frequently asked questions
Cardiac muscle, also called myocardium, is one of three major categories of muscles found within the human body, the other two being smooth muscle and skeletal muscle.
The primary function of cardiac muscle is to pump blood into circulation by generating sufficient force. Cardiac muscle is responsible for keeping the heart pumping and blood circulating around the body.
Cardiac muscle is made up of sarcomeres that allow for contractility. Cardiac muscle cells, or cardiomyocytes, are striated, branched, and contain many mitochondria.
The cardiac muscle contracts and releases involuntarily. The contraction of individual cardiac muscle cells produces force and shortening in these bands of muscle, with a resultant decrease in the heart chamber size and the consequent ejection of the blood into the pulmonary and systemic vessels.
The cardiac muscle is located in the heart and forms the middle layer of the three-layered heart wall.
