Logan Steele
Cardiac muscle, also known as myocardium, is a type of muscle tissue that forms the heart. It is one of the three types of muscle tissues in the body, the other two being skeletal and smooth muscle. Cardiac muscle cells are located in the walls of the heart and are responsible for keeping the heart pumping and blood circulating around the body.
| Characteristics | Values |
|---|---|
| Location | Thick middle layer of the heart |
| Type of muscle | Cardiac muscle is one of the three types of muscle in the body, the other two being skeletal and smooth muscle |
| Surrounding | Surrounded by a thin outer layer called the epicardium (or visceral pericardium) and an inner endocardium |
| Supply and drainage | Coronary arteries supply cardiac muscle, and cardiac veins drain the blood |
| Composition | Cardiac muscle is made up of cardiomyocytes, which are contractile myocytes |
| Function | The primary function of cardiomyocytes is to contract, which generates the pressure needed to pump blood through the circulatory system |
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What You'll Learn
Cardiac muscle is located in the heart wall
Cardiac muscle, also called myocardium, is one of three types of muscle found in the human body, the other two being skeletal and smooth muscle. The myocardium forms the thick middle layer of the heart wall, sandwiched between the inner endocardium and the outer epicardium (also known as the visceral pericardium).
The heart wall is a three-layered structure. The inner endocardium lines the cardiac chambers, covers the cardiac valves, and joins with the endothelium that lines the blood vessels. The endocardium is the innermost layer of the heart wall. It is thin and made up of endothelial cells that are simple squamous in shape. The endocardium lines the heart chambers and covers the heart valves. This layer also joins with the endothelium, which lines the blood vessels. The endocardium is essential for maintaining the shape of the heart chambers and valves, as well as facilitating blood flow through the heart.
The myocardium is the thickest layer of the heart wall. It is composed of cardiac muscle cells or cardiomyocytes, which are responsible for the heart's contractions. These cells are highly specialised and work together in a coordinated manner to pump blood efficiently. The myocardium receives its blood supply from the coronary arteries, which originate from the aortic root and lie on the outer surface of the heart.
The outer layer of the heart wall is the epicardium, also known as the visceral pericardium. It is a thin layer that surrounds and protects the myocardium. The epicardium is composed of simple squamous epithelial cells and is continuous with the endocardium, forming a complete covering around the heart. The epicardium also contains sensory nerve fibres that detect pain and other sensations in the heart.
Cardiac muscle cells are unique in their structure and function. They contain mitochondria, often referred to as the "powerhouses" of the cells, which produce energy in the form of adenosine triphosphate (ATP). Cardiac muscle cells also contain myofibrils, which are composed of myosin and actin proteins. These proteins form the contractile units of the muscle cells, allowing for the powerful and efficient pumping of blood. The coordinated contraction of cardiac muscle cells is essential for maintaining cardiac output and ensuring adequate blood circulation throughout the body. Regular exercise can help strengthen cardiac muscle and improve heart function.
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It forms the thick middle layer of the heart
Cardiac muscle, also called myocardium, makes up the thick middle layer of the heart. It is one of three types of muscle in the human body, the other two being skeletal and smooth muscle. The myocardium is surrounded by a thin outer layer called the epicardium (or visceral pericardium) and an inner endocardium.
The myocardium is made up of sheets of cardiac muscle cells or cardiomyocytes. These cells are responsible for the contractions that allow the heart to pump blood. Each cardiomyocyte needs to contract in coordination with its neighbouring cells, working together to efficiently pump blood from the heart. This coordination is made possible by intercalated discs, which connect cardiac muscle cells. Gap junctions inside the intercalated discs allow electrical impulses to be transferred from one cardiac muscle cell to another.
The primary function of cardiomyocytes is to contract, generating the pressure needed to pump blood through the circulatory system. Coronary arteries supply blood to the cardiac muscle, and cardiac veins drain the blood. Cardiomyocytes are tubular structures composed of chains of myofibrils, which are rod-like units within the cell. The myofibrils consist of repeating sections of sarcomeres, which are the fundamental contractile units of the muscle cells. Sarcomeres are composed of long proteins that organise into thick and thin filaments, called myofilaments. When a cardiac muscle cell contracts, the myosin filament pulls the actin filaments towards each other, causing the cell to shrink.
Cardiac muscle is considered an involuntary tissue because it is controlled unconsciously by regions of the brain stem and hypothalamus. It is also considered an intrinsic or self-controlled tissue because the normal cardiac rhythm is set by specialised pacemaker cardiac muscle cells in the heart itself. These pacemaker cells are only weakly contractile and are located in the sinoatrial node (the primary pacemaker) and the atrioventricular node (secondary pacemaker).
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Cardiac muscle is also called myocardium
Cardiac muscle, also called myocardium, is one of three major categories of muscles in the human body, the other two being smooth muscle and skeletal muscle. The myocardium forms the thick middle layer of the heart, sandwiched between the inner endocardium and the outer epicardium (or visceral pericardium).
The myocardium is made up of sheets of cardiac muscle cells or cardiomyocytes, which are responsible for the contractile function of the heart. Coronary arteries supply blood to the myocardium, and cardiac veins drain it. The contractile function of the heart requires adenosine triphosphate (ATP), which is obtained through various substrates, including fatty acids, carbohydrates, proteins, and ketones. Cardiomyocytes contain mitochondria, which convert oxygen and glucose into ATP.
Cardiac muscle cells appear striated or striped under a microscope due to the alternating filaments of myosin and actin proteins. When a cardiac muscle cell contracts, the myosin filament pulls the actin filaments towards each other, causing the cell to shrink. The coordinated contraction of the sheets of muscle wrapping around the left ventricle allows the ventricle to squeeze in several directions simultaneously, maximising the amount of blood squeezed out of the heart with each heartbeat.
Cardiac muscle is considered an involuntary tissue because it is controlled unconsciously by regions of the brain stem and hypothalamus. It is also considered an intrinsic or self-controlled tissue because the normal cardiac rhythm is set by specialised 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).
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It is one of three types of muscle tissues
Cardiac muscle, also called myocardium, is one of three major categories of muscles found within the human body. The other two muscle tissues are smooth muscle and skeletal muscle.
Cardiac muscle is located in the walls of the heart and is responsible for pumping blood into circulation by generating sufficient force. It is made up of cardiac muscle cells, also known as cardiomyocytes, which are surrounded by an extracellular matrix produced by supporting fibroblast cells. Cardiomyocytes are highly specialised cells that work together to keep the heart pumping and blood circulating throughout the body.
Cardiac muscle contracts in a similar way to skeletal muscle, but with some important differences. Electrical stimulation triggers the release of calcium from the cell's internal calcium store, the sarcoplasmic reticulum. This rise in calcium causes the cell's myofilaments to slide past each other in a process called excitation-contraction coupling. Cardiac muscle cells contain mitochondria, which convert oxygen and glucose into energy in the form of adenosine triphosphate (ATP).
Cardiac muscle is considered an involuntary tissue because it is controlled unconsciously by regions of the brain stem and hypothalamus. It is also considered an intrinsic or self-controlled tissue because the normal cardiac rhythm is set by specialised 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.
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Cardiac muscle cells are called cardiomyocytes
Cardiac muscle, also known as myocardium, is one of three types of muscle in the body, the other two being skeletal and smooth muscle. The myocardium forms the thick middle layer of the heart, sandwiched between the inner endocardium and the outer epicardium (or visceral pericardium). The primary function of the cardiac muscle is to pump blood into circulation by generating sufficient force through contraction.
Cardiac muscle cells, also called cardiomyocytes, are the contractile myocytes of the cardiac muscle. They are the individual cells that make up the cardiac muscle tissue and are responsible for the highly coordinated actions that keep the heart pumping and blood circulating throughout the body. Cardiomyocytes are tubular structures composed of chains of myofibrils, which are rod-like units within the cell. The 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 thick filaments are made of myosin proteins, while the thin filaments contain actin. When a cardiac muscle cell contracts, the myosin filament pulls the actin filaments towards each other, causing the cell to shrink. This contraction generates the pressure needed to pump blood through the circulatory system.
Cardiomyocytes are surrounded by an extracellular matrix produced by supporting fibroblast cells. They are connected to each other by intercalated discs, which consist of three types of cell-cell junctions: actin filament anchoring fascia adherens junctions, intermediate filament anchoring desmosomes, and gap junctions. These junctions allow action potentials to spread between cardiac cells by permitting the passage of ions, resulting in the depolarization of the heart muscle. Gap junctions inside the intercalated discs also enable the propagation of coordinated action potentials from one cell to the next, a process known as electrical coupling.
Specialized modified cardiomyocytes known as pacemaker cells set the rhythm of the heart contractions. These cells are located in the sinoatrial node (the primary pacemaker) on the wall of the right atrium and the atrioventricular node (secondary pacemaker). Pacemaker cells carry the impulses responsible for the beating of the heart and are distributed throughout the heart. They are responsible for generating and sending out electrical impulses and controlling the contractions of the heart.
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Frequently asked questions
Cardiac muscles are located in the walls of the heart.
Cardiac muscles are made up of sarcomeres that allow for contractility.
Cardiac muscles appear striped or striated under a microscope.
Cardiac muscles contract and relax involuntarily to keep the heart pumping and blood circulating around the body.
Cardiac muscle is also called myocardium.
