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Striated muscle tissue is a vital part of the musculoskeletal system, accounting for 40% to 50% of body weight. Skeletal muscle, the most common type of muscle in the body, is a type of striated muscle that enables breathing, movement, and posture maintenance. The striated appearance of skeletal muscle is caused by repeating bands of the proteins actin and myosin, which are present along the length of myofibrils. Cardiac muscle, another type of striated muscle, is responsible for heart contractions and pumping blood throughout the body. In contrast, smooth muscle tissue, which is found in hollow structures like the intestines or blood vessels, does not exhibit striations due to the absence of sarcomeres.
| Characteristics | Values |
|---|---|
| Appearance | Striated or striped |
| Types | Skeletal muscle, cardiac muscle, and most muscle of arthropods |
| Control | Skeletal muscle is under voluntary control, cardiac muscle is under involuntary control |
| Function | Skeletal muscle: breathing, eating, movement, posture maintenance; Cardiac muscle: heart contraction, pumping blood throughout the body, maintaining blood pressure |
| Structure | Skeletal muscle: long and cylindrical; Cardiac muscle: short and branched |
| Nuclei | Skeletal muscle: spindle-shaped nuclei located peripherally; Cardiac muscle: one nucleus per cell, located centrally |
| Composition | Skeletal muscle: actin and myosin myofilaments; Cardiac muscle: densely packed mitochondria, myoglobin, intercalated disks |
| Sarcomeres | Repeating functional units, visible under a microscope as dark and light bands |
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What You'll Learn
- Skeletal muscle is striated due to the repeating bands of actin and myosin proteins
- Cardiac muscle is striated and involuntary, responsible for heart contractions and blood pressure
- Striated muscles enable vital functions like chewing, swallowing, breathing, and movement
- Striated muscles are multinucleated, with spindle-shaped nuclei located peripherally
- Striated muscles are under voluntary control, unlike smooth muscles
Skeletal muscle is striated due to the repeating bands of actin and myosin proteins
Skeletal muscle is the most common type of muscle in the body. It is under voluntary control, meaning an individual can control how and when these muscles work. They are attached to the skeleton and are responsible for breathing, eating, and moving bones.
Skeletal muscle is a type of striated muscle tissue, which features repeating functional units called sarcomeres. Under a microscope, sarcomeres are visible along muscle fibres, giving a striated appearance to the tissue. The two types of striated muscle are skeletal muscle and cardiac muscle.
The striated appearance of skeletal muscle tissue is due to repeating bands of the proteins actin and myosin. These proteins are present along the length of myofibrils, which are long cylindrical structures that lie parallel to the muscle fibre. The myosin proteins form thick filaments, while actin forms thin filaments. The dark A bands and light I bands repeat along the myofibrils, and the alignment of myofibrils in the cell causes the entire cell to appear striated or banded.
Each muscle fibre contains sarcolemma, sarcoplasm, and sarcoplasmic reticulum. The bright bands are referred to as isotropic (I-) bands, and the dark bands are called anisotropic (A-) bands. In the centre of the A-bands runs the M-line, where the myosin filaments are anchored. The sarcomere is the region from one Z line to the next Z line, and many sarcomeres are present in a myofibril, resulting in the striation pattern.
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Cardiac muscle is striated and involuntary, responsible for heart contractions and blood pressure
Muscle tissue is classified into three types according to structure and function: striated (skeletal), smooth, and cardiac. Striated muscle tissue features repeating functional units called sarcomeres, which are visible along muscle fibres, giving a striated appearance to the tissue. The two types of striated muscle are skeletal muscle and cardiac muscle.
Cardiac muscle, also called heart muscle or myocardium, is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. 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. The intercalated discs connect the cardiac cells both mechanically and electrically. The cytoplasm of cardiac muscle cells contains myofibrils and densely packed mitochondria. The fibrils do not run strictly parallel to each other but rather branch in a complex pattern. The cardiac muscle cell has one centrally located nucleus. The structure of the sarcomere resembles that of the skeletal muscle cell. The T-tubules are larger and branched, while the L-system is smaller.
The primary function of cardiac muscle is to pump blood into circulation by generating sufficient force. The cardiac muscle must contract with enough force and blood to supply the metabolic demands of the entire body. The contractions in cardiac muscle will pump blood throughout the body. Contractions in cardiac muscle tissue are due to a myogenic response of the heart's pacemaker cells, which are located in the sinoatrial node (the primary pacemaker) and the atrioventricular node (secondary pacemaker). These cells respond to signals from the autonomic nervous system to either increase or decrease the heart rate. The generation of a cardiac action potential is involuntary and proceeds via a process known as excitation-contraction coupling (ECC). Action potentials travel along the sarcolemma and into the t-tubules to depolarize the membrane. This triggers the release of calcium from the cell's internal calcium store, the sarcoplasmic reticulum. The released calcium attaches to troponin C, causing tropomyosin to detach from the myosin-binding sites on actin. Actin and myosin then form a cross-bridge, and contraction occurs.
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Striated muscles enable vital functions like chewing, swallowing, breathing, and movement
Striated muscles are a vital part of the musculoskeletal system. They are composed of repeating functional units called sarcomeres, which are visible under a microscope, giving the muscles their striated appearance. The two types of striated muscles are skeletal muscles and cardiac muscles. Skeletal muscles are attached to the skeleton and are under voluntary control, whereas cardiac muscles are found in the heart and are under involuntary control.
Striated muscles enable vital functions such as chewing and swallowing, which are the initial steps of digestion. They also facilitate breathing by expanding and contracting the chest cavity, allowing inhalation and exhalation. These muscles are essential for movement, as they contract to move bones and enable various actions. Each muscle can contain thousands of fibres, and these fibres work together to facilitate movement.
The skeletal muscles, which are the most common type of muscle in the body, are responsible for breathing, eating, and moving bones. They make up between 30% and 40% of total body mass and are connected to the skeleton by tendons. These muscles are under voluntary control, allowing conscious movement.
Cardiac muscles, on the other hand, are responsible for heart contractions and pumping blood throughout the body. They have a unique structure with intercalated discs that connect the cardiac cells mechanically and electrically. Their contractions are due to a myogenic response of the heart's pacemaker cells, which respond to signals from the autonomic nervous system to regulate heart rate.
In summary, striated muscles are essential for vital functions such as chewing, swallowing, breathing, and movement. They facilitate these functions through the contraction of skeletal and cardiac muscles, which work together to maintain overall health and enable daily activities.
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Striated muscles are multinucleated, with spindle-shaped nuclei located peripherally
Striated muscles, including skeletal and cardiac muscles, are multinucleated. Each muscle cell contains myofibrils composed of actin and myosin myofilaments. The repeating bands of these proteins along the length of the myofibrils give rise to the striated appearance of the muscle tissue. The dark A bands and light I bands repeat along the myofibrils, resulting in the characteristic striation pattern. The sarcomere, the functional unit of a muscle fibre, is the region from one Z line to the next. Many sarcomeres are present in a myofibril, and their contraction leads to muscle movement.
Skeletal muscles are the most common type of muscle in the body and are under voluntary control. They are attached to the skeleton and play a vital role in everyday activities such as breathing, eating, and movement. Cardiac muscles, on the other hand, are found only in the heart and are responsible for heart contractions and pumping blood throughout the body.
The structure of striated muscles at a cellular level is worth noting. The muscle fibres of striated muscles are cylindrical with blunt ends, contrasting with the spindle-shaped fibres of smooth muscles. Additionally, the nuclei of striated muscle fibres are spindle-shaped and located peripherally. This peripheral location of the nuclei is a distinguishing feature observed under a microscope.
The multinucleated nature of striated muscles is evident in their cellular composition. Each muscle fibre can contain thousands of fibres, and these fibres contract to enable movement. The nuclei of striated muscles play a crucial role in the function and development of these muscles. The spindle shape of the nuclei may be related to the elongated shape of the muscle fibres, ensuring optimal cellular function.
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Striated muscles are under voluntary control, unlike smooth muscles
Striated muscles are characterised by their appearance under a microscope, where repeating functional units called sarcomeres are visible along muscle fibres, giving them a striated or striped appearance. The two types of striated muscle are skeletal muscle and cardiac muscle. Skeletal muscles are attached to some component of the skeleton, and they are under voluntary control. This means that we can consciously control their movement in response to input by nerve cells. For example, when you reach for a book on a shelf, you are using skeletal muscles in your neck, arm and shoulder. These muscles make up between 30% and 40% of your total body mass and include shoulder, hamstring and abdominal muscles. Skeletal muscles are also responsible for breathing, eating and maintaining posture.
Cardiac muscle, on the other hand, is located between the epicardium and endocardium in the heart and is under involuntary control. The contractions in cardiac muscle pump blood throughout the body. Cardiac muscle cells contain one nucleus located in the central region and are connected to each other by intercalated discs.
Unlike skeletal and cardiac muscle, smooth muscle tissue is not striated since it does not contain sarcomeres. Smooth muscle is found in the walls of hollow visceral organs, such as the liver, pancreas and intestines, and is also under involuntary control.
Therefore, striated muscles, particularly skeletal muscles, are under voluntary control, while smooth muscles are not.
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Frequently asked questions
Muscles are striated due to the repeating bands of the proteins actin and myosin that are present along the length of myofibrils.
There are two types of striated muscles: skeletal muscle and cardiac muscle.
Skeletal muscle is the most common type of muscle in the human body. It is a voluntary muscle, meaning we control how and when these muscles work.
Cardiac muscle is only found in the heart. It is an involuntary muscle, meaning it cannot be consciously controlled.
