IB Sports, exercise and health science B.1.3 Muscular Function Key Definitions

Acetylcholinesterase is the enzyme that breaks down acetylcholine at the neuromuscular junction.

Actin: Provides binding sites for myosin.

A high-energy molecule that stores and provides energy for cellular processes, including muscle contraction and metabolism.

Adenosine triphosphate (ATP) is the primary chemical energy currency of the cell. Hydrolysis of ATP releases the energy used for muscle contraction, ion transport, and most other energy-requiring processes.

The agonist, or prime mover, is the muscle primarily responsible for generating force to initiate and execute movement.

An antagonist muscle works opposite to the agonist, lengthening to allow movement while providing control and stability.

Atrophy – A decrease in muscle mass and strength due to disuse, injury, or aging.

Isotonic Concentric – A muscle contraction where the muscle shortens while generating force.

Excitation-contraction coupling is the process linking a muscle action potential to calcium release and contraction.

A fixator (stabilizer) muscle stabilizes a joint so that the agonist can work effectively.

Hypertrophy – An increase in muscle size and strength due to resistance training and consistent use.

Isokinetic – A muscle contraction where movement occurs at a constant speed with variable resistance.

Isometric – A muscle contraction where tension is produced without a change in muscle length.

Isotonic – A type of muscle contraction where the muscle changes length while producing force, including both concentric (shortening) and eccentric (lengthening) contractions.

Isotonic Eccentric – A muscle contraction where the muscle lengthens while controlling force.

A motor unit consists of a single motor neuron and all the muscle fibers it innervates.

Motor Unit – A motor neuron and the muscle fibers it innervates, functioning as a single unit to produce movement.

Muscle tissue is a specialized type of tissue composed of muscle fibers that contract to generate force and facilitate movement.

The process where muscles develop tension and may change length to produce force

Myosin: Forms cross-bridges and performs the power stroke.

The neuromuscular junction (NMJ) is the synapse (connection) between a motor neuron and a skeletal muscle fiber.

A neuron is a nerve cell that transmits electrical and chemical signals to control bodily functions, including movement.

A neurotransmitter is a chemical messenger that transmits signals between neurons and other cells.

pH is a measure of hydrogen ion (H⁺) concentration, determining how acidic or basic a solution is.