Muscular system

Muscle

A primary tissue in the body, responsible for movement, made up of contractile fibers.

Contractility

The ability of muscle tissue to shorten forcibly when stimulated.

Excitability

The ability of muscle cells to respond to nerve signals.

Extensibility

The ability of muscle tissue to be stretched.

Elasticity

The ability of muscle tissue to return to its original shape after being stretched.

Myofilaments

Threadlike structures in muscle cells made of actin and myosin that facilitate contraction.

Sarcoplasm

The cytoplasm of muscle cells.

Sarcolemma

The plasma membrane surrounding muscle cells.

Skeletal muscle tissue

Muscle tissue attached to bones, making up about 40% of body weight, primarily under voluntary control.

Cardiac muscle tissue

Muscle tissue found only in the heart, striated and involuntary.

Smooth muscle tissue

Muscle tissue that occupies the walls of hollow organs, non-striated and involuntary.

Origin

The less movable attachment of a muscle.

Insertion

The more movable attachment of a muscle.

Myofibrils

Long, thread-like structures within muscle fibers that are responsible for muscle contraction. Long rows of repeating sarcomeres make up myofibrils, which contain the proteins actin and myosin.

Fleshy attachments

Connective tissue fibers are short and attach muscle directly to bone.

Concentric contraction

muscle shortens while generating force, often occurring during the lifting phase of an exercise.

eccentric contraction

muscle lengthens while generating force, typically occurring during the lowering phase of an exercise.

Indirect attachments

Connective tissue forms a tendon or aponeurosis to attach muscle to bone.

Neuromuscular junction

The point where a motor neuron meets a muscle fiber.

Slow oxidative fibers

Muscle fibers that produce ATP aerobically and are fatigue-resistant.

Fast glycolytic fibers

Muscle fibers that produce ATP anaerobically and are used for quick bursts of activity.

Prime mover (agonist)

The muscle primarily responsible for a specific movement.

Antagonist

The muscle that opposes or reverses a movement.

Synergist

A muscle that helps the prime mover by adding extra force or reducing unwanted movements.

Fixator

A type of synergist that stabilizes a bone or joint.

Convergent fascicle arrangement

Fascicles converge toward the tendon of insertion from a broad origin.

Types of Pennate

Unipennate, Bipennate, Multipennate

Unipennate

Fascicles insert into one side of the tendon.

Bipennate

Fascicles insert into both sides of the tendon.

Multipennate

Fascicles insert into multiple tendons from various angles.

Circular fascicle arrangement

Fascicles arranged in concentric rings, surrounding external openings.