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The human body has three types of muscle tissue: skeletal, smooth, and cardiac. Cardiac muscle tissue, also known as myocardium, is unique to the heart. It is responsible for the heart's involuntary rhythmic contractions, which pump blood around the body. The rate and force of these contractions are critical in determining the heart's pumping performance and its response to changes in demand.
| Characteristics | Values |
|---|---|
| Types | Cardiac muscle is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. |
| Location | Cardiac muscle is found only in the heart. It forms the thick middle layer of the heart, between the outer layer of the heart wall (the pericardium/epicardium) and the inner layer (the endocardium). |
| Composition | Cardiac muscle is composed of individual cardiac muscle cells (cardiomyocytes) joined by intercalated discs and encased by collagen fibers and other substances that form the extracellular matrix. |
| Function | Cardiac muscle contracts and relaxes involuntarily, keeping the heart pumping blood around the body. The rate and force of contraction determine the normal pumping performance of the heart. |
| Structure | Cardiac muscle has distinct features that allow it to contract in a coordinated fashion and resist fatigue. It contains voltage-gated calcium channels, which skeletal muscle does not possess. |
| Rhythm | The rhythmic contraction of cardiac muscle is regulated by the sinoatrial node of the heart, which serves as the heart's pacemaker. |
| Diseases | Diseases of the heart muscle are called cardiomyopathies and include ischemic conditions like angina and myocardial infarction. |
| Exercise | Regular aerobic exercise can help strengthen cardiac muscle tissue and keep the heart and lungs healthy. |
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What You'll Learn
Cardiac muscle tissue is one of three types of muscle tissue in the body
Cardiac muscle tissue, also known as myocardium, is one of three types of muscle tissue in the body. The other two types are skeletal and smooth muscle tissues. The myocardium is a thick middle layer of the heart, sandwiched between the outer layer of the heart wall (the pericardium or epicardium) and the inner layer (the endocardium).
Cardiac muscle tissue is made up of individual cardiac muscle cells, known as cardiomyocytes, which are joined by intercalated discs and encased by collagen fibres and other substances that form the extracellular matrix. Cardiomyocytes are the contractile myocytes of the cardiac muscle and are responsible for the contractility of the heart and its pumping action. The heart consists mostly of these cardiac muscle cells, which contract and release involuntarily, keeping the heart pumping blood around the body.
Cardiac muscle cells are striated, branched, and contain many mitochondria. Each myocyte contains a single, centrally located nucleus surrounded by a cell membrane known as the sarcolemma. The sarcolemma contains voltage-gated calcium channels, which are specialised ion channels that skeletal muscle does not possess. The calcium channels play a role in the excitation-contraction coupling process, where the release of calcium from the sarcoplasmic reticulum triggers the cell's myofilaments to slide past each other, resulting in contraction.
Cardiac muscle tissue is unique to the heart and is not found anywhere else in the body. It is highly organised and contains various cell types, including fibroblasts, smooth muscle cells, and cardiomyocytes. Regular aerobic exercise can help strengthen cardiac muscle tissue and keep the heart and lungs healthy.
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The tissue forms the heart's thick middle layer
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 one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. The heart is the only organ that is made of cardiac tissue.
Cardiac muscle forms a thick middle layer between the outer layer of the heart wall (the pericardium or epicardium) and the inner layer (the 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. The pericardium is a fibrous sac surrounding the heart, consisting of the epicardium, pericardial space, parietal pericardium, and fibrous pericardium. The myocardium is surrounded by a thin outer layer called the epicardium (AKA visceral pericardium) and an inner endocardium.
Cardiac muscle cells (cardiomyocytes) are the contractile myocytes of the cardiac muscle. They are striated, branched, contain many mitochondria, and are under involuntary control. Each myocyte contains a single, centrally located nucleus surrounded by a cell membrane known as the sarcolemma. The sarcolemma of cardiac muscle cells contains voltage-gated calcium channels, specialized ion channels that skeletal muscle does not possess. The primary function of cardiomyocytes is to contract, which generates the pressure needed to pump blood through the circulatory system.
Cardiac muscle cells form a highly branched cellular network in the heart. They are connected end to end by intercalated discs and are organized into layers of myocardial tissue that are wrapped around the chambers of the heart. 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.
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It contracts and relaxes involuntarily to pump blood
The cardiac muscle, also known as the myocardium, is one of three types of muscle tissues found in the human body, the others being skeletal muscle and smooth muscle. It is composed of individual cardiac muscle cells, or cardiomyocytes, joined by intercalated discs and encased by collagen fibres and other substances that form the extracellular matrix.
Cardiac muscle is an involuntary muscle, meaning it contracts and relaxes without conscious input. This is in contrast to skeletal muscle, which is under voluntary control. The rhythmic contraction of cardiac muscle is regulated by the sinoatrial node of the heart, which serves as the heart's pacemaker. This pacemaker is comprised of specialized cardiomyocytes known as pacemaker cells, which generate electrical impulses that tell the cardiac muscle cells to contract and relax. The rate at which the heart contracts and the synchronization of atrial and ventricular contraction are critical for the efficient pumping of blood and depend on the electrical properties of the cardiac muscle cells.
The individual cardiac muscle cell is a tubular structure composed of chains of myofibrils, which contain repeating sections of sarcomeres. Sarcomeres are the fundamental contractile units of the muscle cells, composed of long proteins that organize into thick and thin filaments, called myofilaments. These myofilaments slide past each other as the muscle contracts and relaxes, producing the formation of "cross-bridges" that cause the contraction of the heart and the generation of force. This process is known as excitation-contraction coupling and is triggered by the release of calcium from the cell's internal calcium store, the sarcoplasmic reticulum.
The contraction of individual cardiac muscle cells produces force and shortening in the bands of muscle that make up the myocardium, resulting in a decrease in the heart chamber size and the consequent ejection of blood into the pulmonary and systemic vessels. This process requires a constant supply of oxygen and nutrients to meet the energy demands of the cardiac muscle, which is provided by the coronary arteries.
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Pacemaker cells control the rate and rhythm of contractions
The heart is the only organ in the human body that is also a muscle. It is made of a special type of muscle tissue called cardiac muscle. This muscle tissue is also called myocardium and is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle.
Cardiac muscle is an involuntary, striated muscle that constitutes the main tissue of the heart wall. It is responsible for the contractility of the heart and, therefore, the pumping action. The cardiac muscle must contract with enough force and blood to supply the metabolic demands of the entire body.
The heart's rhythmic contraction is regulated by the sinoatrial node of the heart, which serves as the heart's pacemaker. Pacemaker cells are a type of specialized cardiomyocyte that sets the rhythm of the heart contractions. They are located in the sinoatrial node (the primary pacemaker) positioned on the wall of the right atrium, near the entrance of the superior vena cava. Other pacemaker cells are found in the atrioventricular node (secondary pacemaker).
Pacemaker cells carry the impulses that are responsible for the beating of the heart. They are distributed throughout the heart and are responsible for several functions. First, they are responsible for being able to spontaneously generate and send out electrical impulses, or action potentials, that tell cardiac muscle cells to contract and relax. The pacemaker cells control heart rate and determine how fast the heart pumps blood.
The action potential of pacemaker cells is divided into three phases instead of five, as phases one and two are absent. They do not require stimulation to initiate their action. This autorhythmicity transpires because of funny current channels, which allow sodium ions to leak continuously into the cell (Phase 4), slowly raising the membrane potential until a certain threshold is reached, causing depolarization of the cell. This subsequently opens calcium channels, causing calcium ions to enter the cell and further raising the membrane potential (Phase 0). After a positive membrane potential is sensed, potassium channels open, causing an outward flow of ions and returning the membrane potential to its resting potential (Phase 3).
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Cardiomyopathies are diseases that affect cardiac muscle tissue
Cardiac muscle, also called heart muscle or myocardium, is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. The heart is the only organ that is made of muscle.
Cardiomyopathy makes it harder for the heart to pump blood to the rest of the body. In most cases, cardiomyopathy causes the heart muscle to become enlarged, thick, or rigid, which weakens the heart. As cardiomyopathy worsens, the heart becomes less able to pump blood throughout the body and incapable of maintaining a normal electrical rhythm. This can lead to heart failure, irregular heartbeats called arrhythmias, or other complications such as heart valve problems.
The symptoms of cardiomyopathy include shortness of breath, fatigue, dizziness, fainting, swelling in the ankles or legs, and chest pain. In some cases, the disease may progress to the point of causing cardiac arrest or cardiogenic shock. Treatment options for cardiomyopathy include medications, lifestyle changes, implanted devices, therapy to lower stress, and in some cases, surgery or other procedures.
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Frequently asked questions
Cardiac muscles are one of three types of muscle tissues in the body, the others being skeletal and smooth muscle. Cardiac muscle tissue forms the heart and is responsible for its pumping action.
Cardiac muscles contract and relax involuntarily, keeping the heart pumping blood around the body. This involuntary movement is controlled by specialised "pacemaker" cells that respond to electrical impulses from the nervous system.
Regular aerobic exercise can help strengthen cardiac muscles and keep the heart and lungs healthy. Cardio exercises include walking, running, biking, and swimming.
