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What are the 3 types of filaments within a muscle and what protein makes up each filament?
The three types of filaments within a muscle are thin filaments, thick filaments, and elastic filaments. Thin filaments are primarily composed of the protein actin, while thick filaments are made up of myosin. Elastic filaments, which help maintain the structure and elasticity of the muscle, are primarily composed of the protein titin. These filaments work together to facilitate muscle contraction and relaxation.
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DO actin and myosin come from muscle fiber?
Yes, actin and myosin are protein filaments found within muscle fibers. Actin is responsible for thin filaments and myosin for thick filaments in muscle contraction.
Thick protein filaments within the A-bands?
The thick protein filaments within the A-bands of sarcomeres are composed primarily of myosin. Myosin filaments contain motor proteins that interact with actin filaments to generate the force needed for muscle contraction. The A-band is the region where myosin filaments are predominantly found, giving it a darker appearance under a microscope.
What substance makes the muscle hard?
When muscles contract, the protein filaments within them slide past one another, causing the muscle to shorten and feel hard. This process involves actin and myosin filaments interacting within muscle fibers, resulting in the characteristic hardness of contracted muscles.
What is Huxley's Sliding Filament Theory?
The sliding filament theory is the explanation for how muscles produce force (or, usually, shorten). It explains that the thick and thin filaments within the sarcomere slide past one another, shortening the entire length of the sarcomere. In order to slide past one another, the myosin heads will interact with the actin filaments and, using ATP, bend to pull past the actin.
What is myofilament?
Myofilaments are the protein fibers within muscle cells that slide past each other to cause muscle contractions. There are two main types of myofilaments: thin filaments, made up of actin protein, and thick filaments, made up of myosin protein. The interaction between these two types of filaments is essential for muscle contraction.
The sliding filament mechanism of muscle contraction involves?
The sliding filament mechanism of muscle contraction involves the interaction between actin and myosin proteins within muscle fibers. When muscles contract, myosin heads bind to actin filaments, causing them to slide past each other and generate force. This process is driven by the hydrolysis of ATP to provide the energy needed for muscle movement.
How does an increase in intracellular calcium cause a muscle fiber to contract?
An increase in intracellular calcium concentration triggers muscle contraction by binding to troponin, a regulatory protein on the actin filaments. This binding causes a conformational change that moves tropomyosin away from the myosin-binding sites on actin, allowing myosin heads to attach to actin. The myosin heads then pivot, pulling the actin filaments inward and resulting in muscle contraction through the sliding filament mechanism. Ultimately, this process is regulated by the calcium levels within the muscle fiber.
What is a cross bridge in a muscle contraction?
A cross bridge in muscle contraction refers to the temporary connection formed between the myosin heads of thick filaments and the actin filaments of thin filaments within a muscle fiber. This interaction occurs during the contraction cycle when calcium ions bind to troponin, causing tropomyosin to shift and expose binding sites on actin. The myosin heads then attach to these sites, pulling the actin filaments toward the center of the sarcomere, which leads to muscle shortening and contraction. This process is a key component of the sliding filament theory of muscle contraction.
Do Sarcomeres produce actin and myosin?
Sarcomeres do not produce actin and myosin. Actin and myosin are protein filaments that are found within sarcomeres and are responsible for muscle contraction. Sarcomeres contain organized arrangements of actin and myosin filaments that slide past each other during muscle contraction.
What happens to muscles when they contract?
When muscles contract, they shorten and generate force, allowing movement to occur. This process is controlled by the nervous system and involves the sliding of protein filaments within the muscle fibers.
What is voluntary muscle?
Involuntary muscles are muscles that are not controllable consciously, and instead contract due to unconscious impulses sent by the autonomic nervous system or certain specialized cells or hormones. Both smooth muscle and cardiac muscle can be classified as involuntary muscles. Smooth muscle is comprised of spindle-shaped cells that have no striations and is found in numerous locations throughout the human body. Cardiac muscle is striated rather than smooth, and is found only within the walls of the heart. Smooth muscles are involuntary muscles composed of thick and thin protein filaments that are homologous to the organelles known as myofibrils found in skeletal muscles. The thin filaments are composed of a globular protein called actin, while the thick ones are made up of a motor protein called myosin. Smooth muscles require extracellular calcium ions to contract: the ions activate a nucleotide called Adenosine triphosphate (ATP), which then activates the myosin filaments. The myosin filaments attach to the actin filaments in a process known as the crossbridge cycle, which causes the thick and thin filaments to slide over each other and contract. When the myosin filaments release the actin filaments, the muscle relaxes.
Where are the myosin filaments found?
Myosin filaments are found in muscle cells, specifically in the thick filaments that make up the myofibrils within the muscle fibers. They are a key component of the sarcomeres, the functional unit of the muscle that is responsible for muscle contraction.
