A&P Unit 3: Muscular System Vocab

Muscle Fiber

A single muscle cell, contracts when stimulated.

Skeletal Muscle

Voluntary muscle tissue attached to bones.

Smooth Muscle

Involuntary muscle tissue found in organs.

Cardiac Muscle

Involuntary muscle tissue only found in the heart.

Sarcomere

Basic structural and functional unit of a muscle fiber, composed of actin and myosin.

Actin

Thin protein filament in sarcomere.

Myosin

Thick protein filament in sarcomere.

Sliding Filament Theory

Explanation of how muscles contract. Actin and myosin have to slide against each other to shorten the sarcomere and contract the muscle.

Neuromuscular Junction

Point where motor neuron meets a muscle fiber, transmitting a signal, and triggering muscle contraction.

Motor Unit

Motor neuron and all of the muscle fibers it controls.

Acetylcholine (ACh)

Neurotransmitter released by motor neurons to initiate muscle contraction.

Calcium Ions (Ca^+²)

Ions released from the sarcoplasmic reticulum in muscle fibers that bind to proteins and allow the actin-myosin interaction for muscle contraction.

ATP (Adenosine Triphosphate)

Energy-carrying molecule.

Isotonic Contraction

Muscle contraction where muscle changes length while producing force.

Isometric Contraction

Muscle contraction where muscle does NOT change length while generating force.

Agonist (Prime Mover)

Muscle that’s primarily responsible for movement.

Antagonist

Muscle opposing the agonist.

Synergist

Muscle assisting agonist in movement, providing stability.

Fixator

Muscle that stabilizes the origin of the agonist.

Muscle Tone

State of contraction in resting muscles, helping maintain posture.

Hypertrophy

Enlargement of muscle fibers.

Atrophy

Decrease in muscle mass.

Muscle Fatigue

Decline in muscle’s ability to generate force.

Lactic Acid

Byproduct of anaerobic respiration in muscles.

Sarcoplasmic Reticulum

Network of tubules in muscle cells that store and release calcium ions for muscle contraction.

Tendon

Fibrous connective tissue attached to muscle and bone for movement.

Fascia

Layer of connective tissue that surround muscles and organs.

Origin

Point where muscle attaches to bone that moves in muscle contraction.