Muscle Composition and Structure

A fundamental type of tissue responsible for movement in organisms. It is formed by cells that are specialized for contraction.

Muscle tissue that contains a highly organized arrangement of proteins called myofilaments, giving it a distinctive striped appearance. It is responsible for voluntary movements.

A type of striped muscle tissue responsible for the contraction of skeletal muscles. It is under voluntary control, meaning we can consciously control its movement.

A type of striped muscle tissue found only in the heart. It contracts involuntarily, ensuring a continuous heartbeat.

Muscle tissue that lacks a striated appearance. It is responsible for involuntary movements, often in internal organs.

A single muscle cell, also known as a muscle fiber. It is elongated, cylindrical, and multinucleated.

The cytoplasm of a muscle cell. It contains numerous organelles, including myofibrils.

The plasma membrane of a muscle cell. It has invaginations called T-tubules that connect the cell's exterior to the interior.

A type of muscle activity in response to a stimulus. It might lead to muscle shortening, resulting in changes in length or tension.

The force developed within a muscle. It reflects the amount of tension generated by the muscle fibers.

The force that a muscle must overcome to produce movement. It often refers to the weight of an object.

The rate at which a muscle can perform work. It is determined by both force and velocity of movement.

A type of muscle contraction where the muscle length stays the same, despite generating force. Think of holding a heavy object.

A type of muscle contraction where the muscle length changes while generating force. Think about lifting a weight.

A type of isotonic contraction where the muscle shortens because the generated tension is greater than the load.

A type of isotonic contraction where the muscle lengthens because the generated tension is less than the load.

The area between two Z lines, which are the boundaries of a sarcomere.

Thick filaments are primarily composed of myosin, a protein that has a globular head that interacts with actin, the protein that makes up thin filaments.

Thin filaments are primarily composed of actin, a protein arranged in a helical structure. Actin binds to troponin and tropomyosin, which play crucial roles in regulating muscle contraction.

Calcium ions are released from the sarcoplasmic reticulum, a specialized organelle within muscle cells. This release triggers a conformational change in tropomyosin, exposing binding sites on actin for myosin to interact with.

ATP (adenosine triphosphate) provides energy for muscle contraction. It binds to the myosin head and is hydrolyzed, releasing energy that fuels the power stroke, the sliding of myosin along actin.

The A band represents the entire length of the thick filament. It remains constant during contraction because the thick filaments themselves don't shorten.

The I band contains only thin filaments. It shortens during contraction because the thin filaments slide over the thick filaments.

The sliding filament model describes the process of muscle contraction. Thin filaments actively slide past stationary thick filaments, causing the sarcomere to shorten.

Muscle fibers that contract slowly, use aerobic metabolism, and are resistant to fatigue. They are often called "red" fibers due to their high myoglobin content.

Muscle fibers that contract quickly, use anaerobic metabolism, and fatigue quickly. They are often called "white" fibers due to their lower myoglobin content.

A subtype of Type II muscle fibers that have a faster contraction speed than Type IIa fibers. They are larger, stronger, and faster.

The process of changing the characteristics of muscle fibers in response to training and environmental cues.

A protein phosphatase that plays a key role in muscle remodeling. It dephosphorylates NFAT, allowing it to translocate to the nucleus and activate muscle remodeling genes.

A transcription factor that is activated by calcineurin and promotes muscle remodeling by activating genes.

The process of increasing the number of capillaries in muscle tissue, which improves oxygen delivery and resistance to fatigue.

The process of increasing the size of muscle fibers, which leads to increased strength and muscle mass.

A transcription factor regulating skeletal muscle development, activated by class II histone deacetylases (IIHDACs). It promotes slow fiber formation and myocyte survival.

Mitochondria's ability to adapt to various stimuli, like exercise, leading to changes in muscle fiber types and increased antioxidant enzyme expression.

The initial stage of anatomical muscle injury, lasting 1-6 days, marked by disruption of muscle cells and an inflammatory response.

The second stage of muscle injury, lasting 3-20 days, during which the body builds bridges and a network of capillaries and connective tissue.

The final stage of muscle injury, from day 20 onwards, where collagen fibers are arranged to form a functional scar.

A type of exercise where the maximum strength on one end of a biarticular muscle cannot be reached if the other end is stretched.

The concept of carefully managing fatigue during exercise to prevent muscle injury.

The importance of considering the muscle's fatigue level when prescribing exercises, avoiding demanding activities when the muscle is highly fatigued.