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Chapter 6:

The Muscular System

TermDefinition
Endomysium A delicate connective tissue sheath that encloses each muscle fiber
Perimysium A coarser fibrous membrane that wraps several sheathed muscle fibers
Fascicle A bundle of fibers
Epimysium Tough “overcoat” of connective tissue that bind many fascicles
Tendons Strong, cordlike blend of the epimysia (dense fibrous tissue attaching a muscle to bone)
Aponeuroses Strong, sheetlike blend of the epimysia (fibrous or membranous connecting a muscle and the part it moves)
Intercalated Discs Special junctions that joint branching cells (cardiac muscle fibers)
Muscular System Organ system consisting of skeletal muscles and their connective tissue attachments
Sarcolemma Plasma membrane that many oval nuclei can be seen just beneath
Myofibrils Long ribbonlike organelles which nearly fill the cytoplasm and push the nuclei aside
Sarcomeres Tiny contractile units --- aligned end-to-end like boxcars in a train along the length of the myofibrils
Myofilaments Two types of threadlike protein within each of out "boxcar" sacomeres
Thick Filaments Myosin filaments --- made mostly of bundled molecules of the protein myosin, but they also contain ATPase enzymes, which split ATP to generate the power for muscle contraction
Cross Bridges Projections or myosin heads when they link the thick and thin filaments together during contraction
Thin Filaments Actin filaments --- Composed of the contractile protein called actin, plus some regulatory proteins that play a role in allowing (or preventing) myosin head-binding to actin
Sarcoplsmic Reticulum (SR) Another very important muscle fiber organelle --- a specialized smooth endoplasmic reticulum
Motor Unit One neuron and all the skeletal muscle cells it stimulates
Axon Nerve fiber --- a long threadlike extension of the neuron that reaches the muscle and branches into a number of axon terminals
Axon Terminals Each forms junctions with the sarcolemma of a different muscle cell
Neuromuscular Junctions The junctions that are formed between the axon terminals and the sarcolemma
Synaptic Cleft The gap between the nerve endings and the muscle cells' membranes that is filled with tissue (interstitial) fluid
Neurotransmitter A chemical that is released when the nerve impulse reaches the axon terminals
Acetylcholine (ACh.) The specific neruotransmitter that stimulates skeletal muscle cells
Action Potential An electrical current
Creatine Phosphate (CR) The unique high-energy molecule that is found in muscle fibers but not other cell types
Aerobic Respiration Occurs in the mitochondria and involves a series of metabolic pathways that use oxygen
Anaerobic Respiration Occurs in the mitochondria and involves a series of metabolic pathways that do not use oxygen
Isotonic Contractions “Same tone”/tension --- the myofilaments are successful in their sliding movements, the muscle shortens, and movement occurs
Isometric Contractions “Same measurement”/length --- the myofilaments are “skidding their wheels,” and the tension in the muscle keeps increasing --- trying to slide =, but the muscle is pitted against some more or less immovable object
Muscle Tone The state of continuous partial contractions
Prime Mover The muscle that has the major responsibility for causing a particular movement
Antagonists Muscles that oppose or reverse a movement
Created by: sarah23me1