Anatomy of Skeletal Muscle

The outer layer of connective tissue that encases the entire muscle.

Each muscle fiber is encased in a thin layer of connective tissue.

A bundle of muscle fibers is called a fasciculus. Each bundle is surrounded by a thin layer of connective tissue.

The functional unit of a muscle fiber responsible for muscle contraction.

Each muscle fiber contains many myofibrils, which are the contractile elements of the fiber, responsible for the muscle's shortening during contraction.

The plasma membrane that surrounds a muscle fiber.

The fluid portion of a muscle fiber that contains the myofibrils and other cellular machinery.

A single muscle cell, also known as a muscle fiber.

The process of breaking down ATP (adenosine triphosphate) into ADP (adenosine diphosphate) and a phosphate group (Pi). This releases energy. Energy is needed for muscle contraction.

The myosin head is 'cocked' or energized, ready to bind to actin. This happens after ATP hydrolysis and the release of Pi.

The myosin head binds to the actin filament, forming a cross-bridge. This is the first step in the muscle contraction cycle.

The myosin head pivots and bends, pulling the actin filament towards the M line. This shortens the sarcomere and causes muscle contraction. ADP is released during this process.

The myosin head detaches from the actin filament after ATP binds. This readies the myosin head for the next cycle.

An electrical signal from the brain or spinal cord sent to a motor neuron.

A motor neuron and all the muscle fibers it innervates.

The principle stating that a motor neuron either fully activates all the muscle fibers in its unit, or none at all.

Fine motor control requires smaller motor units with fewer muscle fibers per neuron.

Muscles with more general functions have larger motor units with many muscle fibers per neuron.

A specialized synapse where a motor neuron communicates with a muscle fiber.

The neurotransmitter released at the NMJ to initiate muscle contraction.

A fundamental process in muscle contraction that describes the sliding of the actin and myosin filaments past each other.

Muscle fibers with a high capacity for aerobic metabolism, slow contraction speed, and high resistance to fatigue.

Muscle fibers with a high capacity for anaerobic metabolism, fast contraction speed, and low resistance to fatigue.

A type of fast twitch muscle fiber with moderate aerobic capacity and high anaerobic capacity. These fibers are more adaptable and can use both energy systems effectively.

A type of fast twitch muscle fiber with the highest anaerobic capacity and the lowest aerobic capacity. These fibers are best for very short, powerful movements. They are also known as "fast glycolytic" fibers.

The enzyme responsible for splitting ATP, providing energy for muscle contraction. Different types of myosin ATPase determine the speed of contraction.

The process of obtaining a small sample of muscle tissue to examine its structural and functional properties. This technique can be used to determine the fiber type composition of a muscle.

A technique used to separate proteins based on their size and charge. This can be used to determine the type of myosin ATPase present in a muscle fiber, revealing its contractile speed.

A procedure used to isolate and study individual muscle fibers, often from the vastus lateralis muscle. This involves extracting a small sample of muscle tissue and then separating individual fibers for analysis.

The study of the functional characteristics of muscle fibers. This involves analyzing the strength, velocity, and other properties of individual muscle fibers to understand their role in muscle contraction.

A specific classification of muscle fibers characterized by their fast contractile speed, high force production capabilities, and dependence on anaerobic metabolism. These fibers are often involved in powerful, short-duration activities.

A type of muscle fiber characterized by its slow contractile speed, high endurance capacity, and reliance on aerobic metabolism. These fibers are often involved in sustained, low-intensity activities.

A common site for muscle biopsies, which are used to study muscle fiber types and functions.

A local anesthetic used to numb the area before a muscle biopsy, reducing discomfort for the individual.

A specific type of muscle fiber with characteristics falling between those of Type IIa and Type IIx fibers. These fibers offer a balance of speed and endurance, making them versatile for various activities.

Marathon athletes have a significantly higher percentage of slow-twitch (Type I) muscle fibers, which are responsible for endurance. This allows them to sustain long-duration activity.

Sprinters have a larger proportion of fast-twitch (Type II) muscle fibers, particularly Type IIa, which are crucial for generating quick bursts of power during running.

Endurance training leads to an increase in slow-twitch (Type I) fibers, enhancing the body's ability to sustain activity over a more extended period.

Sprint training promotes an increase in fast-twitch (Type II) fibers, primarily Type IIa, which are essential for generating powerful, short-duration movements.

The type of muscle fiber alone cannot determine an athlete's success. Other factors like training, genetics, and nutrition play a vital role.

The primary muscle responsible for a movement, also known as the prime mover.

The muscle that opposes the agonist, preventing excessive movement and controlling joint stability.

Muscles that assist the agonist in performing a movement, either by directly aiding the action or refining its direction.

Muscle contraction where the muscle shortens while generating force, resulting in movement.

Muscle contraction where the muscle lengthens while generating force, controlling movement.

Muscle contraction where the muscle generates force without changing length, maintaining a static position.

Muscle contraction performed at a constant speed, regardless of the force applied. This is achieved using specialized equipment.

Muscle contraction that allows for varying speeds and resistance, providing a more dynamic and challenging exercise experience. This is typically achieved with specialized equipment.

The ability of a muscle to generate force is influenced by various factors, including the angle of the joint, the speed of contraction, the length of the muscle fibers, the number of motor units activated, and the size of the muscle.

Every joint has an optimal angle at which the muscles crossing it can produce the greatest amount of force.