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Muscle fiber

An individual muscle cell

Flexor

A muscle that closes a joint; brings bones together

Fascicle

A group of muscle fibers bundled together in a whole muscle

Sarcomere

An individual unit of contraction in muscle protein

Epimysium

The strong connective tissue surrounding a muscle

Neurotransmitter

A chemical message produced by a neuron; stimulates a muscle

Tendon

Strong connective tissue linking a muscle to a bone

Motor plate

The location on muscle fibers where neurotransmitters bind

Motor neuron

A nerve that connects the central nervous system to a muscle

Extensor

A muscle that opens a joint; moves bones away from each other

Atrophy

Decrease in muscle

Hypertrophy

Increase in muscle size

Recruitment

activating more motor units to produce a stronger muscle contraction.

Muscle Motor Unit

A motor neuron and all the muscle fibers it stimulates.

Neurotransmitter

A chemical released by a neuron that transmits a signal to another cell

Sphincter muscle

A circular muscle that controls the opening and closing of a passageway.

Aerobic Cellular Respiration

Process that uses oxygen to produce ATP (energy) in cells.

Flexor

A muscle that decreases the angle of a joint (bends a body part).

Extensor

A muscle that increases the angle of a joint (straightens a body part).

Point of Origin

The fixed attachment point of a muscle, usually on a less movable bone.

Point of Insertion

The movable attachment point of a muscle, usually on a bone that moves.

Neuromuscular Junction

The synapse (connection) between a motor neuron and a muscle fiber.

Muscle Fatigue

A condition in which a muscle loses its ability to contract effectively.

Muscle Tone

Continuous, partial muscle contraction that maintains posture and readiness.

Myoglobin

A protein in muscle cells that stores oxygen.

Fast twitch muscle

Muscle fibers that contract quickly and powerfully but fatigue easily.

Slow twitch muscle

Muscle fibers that contract slowly, resist fatigue, and are used for endurance.

Actin and Myosin Protein

Contractile proteins that slide past each other to cause muscle contraction.

Tendon

A strong connective tissue that attaches muscle to bone.

Fascicle

A bundle of muscle fibers surrounded by connective tissue.