Logan Steele
Cardiac muscle, also known as myocardium or heart muscle, is a specialised form of muscle tissue that is only found in the heart. It is one of three types of muscle tissues, the other two being skeletal muscle and smooth muscle. The cardiac muscle forms a thick middle layer of the heart wall, constituting the main tissue of the heart wall. It is composed of individual cardiac muscle cells, or cardiomyocytes, that are joined by intercalated discs and encased by collagen fibres and other substances that form the extracellular matrix. The cardiac muscle is unique in its structure and function, with specialised pacemaker cells that set the rhythm of the heart contractions and allow it to pump blood throughout the body.
| Characteristics | Values |
|---|---|
| Found in | Heart |
| Involuntary or voluntary | Involuntary |
| Controlled by | Intrinsically controlled |
| Striated or non-striated | Striated |
| Branched or non-branched | Branched |
| Number of nuclei | One |
| N/A | Autorhythmicity |
| N/A | High contractile strength and endurance |
| N/A | Quick electrochemical signal transmission |
| N/A | Intercalated discs |
| N/A | Gap junctions |
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What You'll Learn
Cardiac muscle is unique to the heart
Cardiac muscle, also called myocardium or heart muscle, is a unique type of muscle tissue that is only found in the heart. It constitutes the main tissue of the heart wall, forming a thick middle layer between the outer layer of the heart wall (the pericardium) and the inner layer (the endocardium).
The cardiac muscle is composed of individual cardiac muscle cells, or cardiomyocytes, joined by intercalated discs. These discs form tight junctions between the cells, preventing them from separating during the powerful contractions of the heart. They also facilitate the rapid transmission of electrochemical signals from cell to cell, allowing the cardiac muscle to contract in a coordinated manner.
Cardiac muscle cells are shorter and more rectangular than skeletal muscle cells, with each cell containing a single nucleus and many mitochondria. The presence of mitochondria provides the energy required for the cardiac muscle to contract. Additionally, cardiac muscle cells have a branched shape, allowing each cell to be in contact with three or four other cardiac muscle cells. This branching structure contributes to the coordinated contractions of the heart.
One of the most important features of cardiac muscle is its ability to set its own contraction rhythm. This is achieved through specialised pacemaker cells that are distributed throughout the heart. These pacemaker cells receive inputs from the nervous system and adjust the heart rate according to the body's needs. They carry impulses that stimulate the other cardiac muscle cells to contract, resulting in the continuous beating of the heart.
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It has a unique structure
Cardiac muscle tissue is a unique form of muscle tissue that is only found in the heart. It makes up the bulk of the heart's mass and forms a thick middle layer of the three-layered heart wall, known as the myocardium.
Cardiac muscle tissue is composed of individual cardiac muscle cells, or cardiomyocytes, joined by intercalated discs. These discs form tight junctions between the cells, preventing them from separating during the powerful contractions of the heart. They also facilitate the rapid transmission of electrochemical signals from cell to cell, allowing the cardiac muscle tissue to contract in a coordinated manner.
Each cardiac muscle fiber contains a single nucleus and is striated, or striped, with light and dark bands. This striated appearance is due to the parallel arrangement of actin and myosin filaments within the cell. The dark bands represent areas of thick protein filaments made of myosin proteins that block light, while the light bands represent thin filaments made of actin protein that allow light to pass through. During muscle contraction, myosin pulls the actin filaments together, causing the muscle cell to shrink and contract.
Cardiac muscle cells are narrower, shorter, and more rectangular than skeletal muscle cells, with a branched shape that allows each cell to be in contact with three or four other cardiac muscle cells. This unique structure, along with the presence of many mitochondria, provides cardiac muscle tissue with the strength and endurance to contract continuously and powerfully throughout an entire lifetime.
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Cardiac muscle is intrinsically controlled
Cardiac muscle, also called myocardium or heart muscle, is one of three types of muscle tissues, the others being skeletal muscle and smooth muscle. It is found only in the heart and makes up the bulk of the heart's mass. The cardiac muscle forms a thick middle layer of the three-layered heart wall, with the outer layer being the pericardium (or epicardium) and the inner layer being the endocardium.
The cardiac muscle cells are shorter than skeletal muscle cells and form a network of many branches between the cells. They are also narrower and much shorter than skeletal muscle cells, being about 0.02 mm wide and 0.1 mm long, and are more rectangular than smooth muscle cells. Cardiac muscle cells have a branched shape, with each cell in contact with three or four other cardiac muscle cells. This branching structure, along with the presence of intercalated discs, allows the cells to lock together tightly and enables the quick passage of electrochemical signals between cells.
The intercalated discs are regions of overlapping, finger-like extensions of the cell membrane that form tight junctions between the cardiac muscle cells. These junctions ensure that the cells do not separate under the strain of pumping blood and facilitate the rapid transmission of electrochemical signals from cell to cell. This allows the cardiac muscle tissue to contract very quickly in a wave-like pattern, enabling the efficient pumping of blood throughout the body.
The unique structure and intrinsic control of cardiac muscle tissue are essential for its function in pumping blood powerfully and continuously throughout an entire lifetime.
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It is made up of many interlocking muscle cells
Cardiac muscle tissue is a unique form of muscle tissue that has evolved to pump blood throughout the body. It is made up of many interlocking muscle cells, also known as cardiomyocytes, which give the tissue its properties. Each cardiac muscle fibre contains a single nucleus and is striated, or striped, with light and dark bands when viewed under a microscope. The dark bands represent areas of thick protein filaments made of myosin proteins that block light passing through the cell, and the light bands are made of thin filaments of actin protein that allow light to pass through.
The cardiac muscle cells are branched, with each cell in contact with three or four other cardiac muscle cells. They are joined by intercalated discs, which are regions of overlapping, finger-like extensions of the cell membrane. These intercalated discs form tight junctions between the cells, preventing them from separating under the strain of pumping blood. They also allow electrochemical signals to pass quickly from cell to cell, enabling the cardiac muscle tissue to contract very quickly in a wave-like pattern to pump blood throughout the body.
The intercalated discs contain gap junctions, which transfer stimulation from one cardiac muscle cell to the next, allowing the muscle to contract in a coordinated way. The passage of signals from cell to cell is vital to the function of the heart as a whole. Another unique feature of cardiac muscle tissue is autorhythmicity, or the ability to set its own contraction rhythm. This is due to the presence of specialised pacemaker cells that stimulate the other cardiac muscle cells and are distributed throughout the heart.
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Cardiac muscle is striated
Cardiac muscle tissue is one of three types of muscle tissues in the body, the other two being skeletal muscle tissue and smooth muscle tissue. It is found only in the heart and constitutes the main tissue of the heart wall.
The presence of myofibrils and many mitochondria in cardiac muscle cells provides them with great strength and endurance to pump blood throughout a lifetime. The cardiac muscle cells are narrower and shorter than skeletal muscle cells, with each cell containing a single nucleus.
The intercalated discs formed between the cardiac muscle cells are another unique feature of cardiac muscle tissue. These discs allow the cardiac muscle cells to be 'glued' together and facilitate the quick passage of electrochemical signals between cells.
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Frequently asked questions
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 cardiac muscle is made up of many interlocking cardiac muscle cells, or fibres, that give the tissue its properties. These fibres contain a single nucleus and are striated, or striped, because they appear to have light and dark bands when seen through a microscope. When the muscle fibres contract, myosin pulls the actin filaments together like an accordion to shrink the muscle cell and make it contract.
Cardiac muscle is unique because it is the only muscle that is found in the heart and makes up the bulk of the heart's mass. It is also unique in the way that contraction is initiated and regulated. It has incredibly high contractile strength and endurance, and because the heart maintains its own rhythm, cardiac muscle has developed the ability to quickly spread electrochemical signals so that all of the cells in the heart can contract together as a team.
Intercalated discs are found at the ends of each cardiac muscle cell and form tight junctions between the cells so that they cannot separate under the strain of pumping blood and so that electrochemical signals can be passed quickly from cell to cell.
