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Voluntary muscles, also known as skeletal muscles, are under conscious control. They are attached to bones and allow us to perform a wide range of movements and functions. Skeletal muscles are composed of bundled units of fascicles, made up of muscle fibres or muscle cells. These muscles can convert chemical energy into mechanical energy to cause voluntary muscle contraction and movement. They make up 30% to 40% of our total body mass.
| Characteristics | Values |
|---|---|
| Type of muscle | Striated muscle tissues |
| Controlled by | Somatic nervous system |
| Consists of | Multiple bundles of cells and muscle fibres |
| Function | Contraction and movement |
| Location | Attached to bones by tendons |
| Composition | Units of fascicles, made up of muscle fibres or muscle cells |
| Structure | Striped structure due to myofilaments |
| Contraction | Occurs when myofilaments move closer together |
| Stimulated by | Neurotransmitter acetylcholine |
| Examples | Biceps, triceps, quadriceps, abdominals |
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What You'll Learn
Voluntary muscles are under the control of the somatic nervous system
Voluntary muscles, such as skeletal muscles, are under the control of the somatic nervous system. They are composed of multiple bundles of cells and muscle fibres, which are attached to bones and the skin. Skeletal muscles make up 30% to 40% of the human body mass and are responsible for a wide range of movements and functions. They are called voluntary muscles because they are under the conscious control of the individual.
The somatic nervous system sends signals to the skeletal muscles, allowing them to contract and relax, resulting in movement. Skeletal muscles can convert chemical energy into mechanical energy, causing muscle contraction and facilitating movement. Each skeletal muscle is made up of bundled units of fascicles, which are composed of muscle fibres or muscle cells. These muscle fibres are further divided into myofibrils, containing thick and thin myofilaments that give skeletal muscles their characteristic striated or striped structure.
The contraction of skeletal muscles occurs when the myofilaments move closer together due to stimulation by the neurotransmitter acetylcholine. This neurotransmitter communicates with the muscle fibres, causing them to contract and resulting in movement. Examples of skeletal muscles include major muscle groups such as the biceps and triceps in the arms, quadriceps in the legs, and abdominal muscles.
Voluntary muscles are essential for various bodily functions, including chewing and swallowing, which are the initial stages of digestion. They also enable vital functions such as expanding and contracting the chest cavity during inhalation and exhalation. The ability to consciously control these muscles allows humans to perform a diverse range of movements and activities.
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They are also known as skeletal muscles
Voluntary muscles are also known as skeletal muscles because they are attached to bones by tendons. These muscles are under voluntary control, meaning that they can be consciously controlled. They are also known as skeletal muscles because they are part of the voluntary muscular system.
Skeletal muscles are composed of bundled units of fascicles, which are made up of muscle fibers or muscle cells. Each muscle fiber is divided into myofibrils that contain thick (myosin) and thin (actin) myofilaments. The myofilaments give skeletal muscles their characteristic striated or striped structure. This structure is due to the arrangement of the sarcomeres.
The contraction of skeletal muscles occurs due to stimulation by the neurotransmitter acetylcholine, which communicates with the muscle fiber. This contraction causes voluntary muscle movement. Skeletal muscles can convert chemical energy into mechanical energy, allowing for voluntary muscle contraction and movement.
Examples of skeletal muscles include major muscle groups that control the movement of the biceps and triceps in the arms, the quadriceps in the legs, and the abdominals. These muscles are essential for various physical activities and allow for conscious movement and control.
Disorders such as amyotrophic lateral sclerosis (ALS) and Charcot-Marie-Tooth disease can affect the nerves that control voluntary movement, leading to muscle weakness and atrophy. It is important to understand the structure and function of skeletal muscles to comprehend the impact of such disorders and develop effective treatments.
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They are attached to bones and skin
Voluntary muscles, also known as skeletal muscles, are attached to bones and skin. They are responsible for allowing the body to move by contracting and relaxing. These muscles are under the control of the somatosensory nervous system.
Skeletal muscles are attached to bones by tendons, which are made of strong fibrous connective tissue. They attach to bones at two or more places. If the attachment is on a bone that remains immobile during an action, it is called an origin. If the attachment is on a bone that moves during the action, it is called an insertion. An example of this is the triceps brachii, which has three origins (two on the humerus and one on the scapula) and one insertion (on the ulna).
Voluntary muscles are also attached to the skin. For example, the biceps muscle in the front of the upper arm is a flexor, and when it contracts, the triceps muscle at the back of the upper arm acts as an extensor to straighten the elbow. These muscles work in pairs to allow for smooth, coordinated motion.
The skeletal system, made up of bones, joints, and ligaments, provides support for the body and helps form its shape. Bones are connected to other bones by ligaments, which are long, fibrous straps that strengthen the joints. Cartilage, a flexible, rubbery substance in the joints, supports and protects the bones.
Voluntary skeletal muscles play a crucial role in maintaining posture, generating heat in the body, and protecting organs. They also help with everyday movements that we consciously control, such as lifting an arm or running.
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They are responsible for breathing and chewing
Voluntary muscles are skeletal muscles that attach to bones and can be consciously controlled. They are composed of bundled units of fascicles, made up of muscle fibres or muscle cells. The contraction of these muscles occurs due to stimulation by the neurotransmitter acetylcholine, which communicates with the muscle fibre.
Voluntary muscles are responsible for breathing and chewing. The diaphragm, a dome-shaped muscle below the lungs, is the main muscle used for breathing. It separates the chest cavity from the abdominal cavity and works with the muscles in the chest and abdomen to create a vacuum around the lungs, allowing air to flow in. The intercostal muscles between the ribs also play a role in breathing, especially during physical activity. The abdominal muscles help to breathe out when breathing fast.
The muscles of the face, mouth, and pharynx control the lips, tongue, and soft palate, which are also essential for breathing. The facial muscles involved in chewing include the lateral pterygoid, masseter, medial pterygoid, and temporalis muscles. These muscles help control the movement of the jaw, allowing for chewing and grinding food. They also assist in bringing the teeth together and controlling facial expressions.
The accessory muscles of mastication include the buccinator and the suprahyoid, infrahyoid, and geniohyoid muscles. The buccal and facial muscles involved in chewing include the buccinator, a thin muscle in the cheek, and the depressor anguli oris and depressor labii inferioris, which help control the chin and lower lip movements.
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Weakness in voluntary muscles can be a symptom of health issues
Voluntary muscles, also known as skeletal muscles, are long, multinucleated cells containing sarcomeres arranged into bundles. These muscles are composed of cylindrical fibers and are usually attached to bones and the skin. They play a crucial role in enabling movement through contraction and relaxation. The brain sends signals through the spinal cord and nerves to a voluntary muscle, prompting it to contract.
Weakness in voluntary muscles can be a symptom of various health issues. For instance, neuromuscular disorders, such as muscular dystrophies, amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and autoimmune diseases like myasthenia gravis, can lead to significant muscle weakness. Myasthenia gravis, an autoimmune disease, causes the body to produce antibodies that interfere with muscle contraction, resulting in weakness. Similarly, electrolyte imbalances, which alter levels of sodium, potassium, calcium, or magnesium, can cause muscle weakness.
In addition, certain medications, chronic conditions, and infections can contribute to muscle weakness. For example, fibromyalgia, a chronic condition, causes muscle pain and weakness. Sleep disorders, such as insomnia, can also lead to daytime muscle weakness and fatigue. Furthermore, the flu virus, Lyme disease, and HIV are associated with muscle weakness.
Age-related factors, such as sarcopenia, a condition characterised by the loss of muscle mass and strength, can also result in muscle weakness. This typically affects older adults and is accompanied by symptoms such as grip weakness, slow gait speed, and unintentional weight loss. Additionally, muscle weakness can be a sign of a stroke or other serious health issues.
If you experience persistent muscle weakness without an apparent cause, it is important to seek medical advice to determine the underlying cause and receive appropriate treatment.
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Frequently asked questions
A voluntary muscle is a muscle that is under voluntary control, such as most striated muscles.
Skeletal muscles are an example of voluntary muscles. These include major muscle groups that control the movement of the biceps and triceps in your arm, quadriceps in the legs, or your abdominals.
Voluntary muscles are made of long, multinucleated cells, containing sarcomeres arranged into bundles. They are composed of cylindrical fibers and are usually attached to bones and the skin.
Voluntary muscles work by contracting and relaxing to allow the body to move. Their actions are mainly under the control of the somatosensory nervous system.
Involuntary muscles are not under conscious control. Their contraction and relaxation are regulated by the autonomic nervous system, which controls the activity of organs and blood vessels.
