| Term | Definition |
|---|
| Myoblasts | precursors to muscle cells, fuse together |
| Axial Muscles | muscles of the head, neck, and trunk |
| Appendicular Muscles | muscles of the limbs |
| Insertion | distal attachment of muscle to bone |
| Origin | proximal attachment of muscle to bone |
| Extensors | triceps brachii: long head and lateral head |
| Flexors | biceps brachii, brachialis |
| Skeletal muscle | most abundant tissue in the body; forms about 40-50% of adult mass; critical in facial expressions |
| Skeletal muscle | the ultimate force generator in the body |
| Skeletal muscle properties | extensibility (stretch)/elasticity (recoil), contractility, conductivity, excitability |
| Extensibility and elasticity | enable the muscle to be stretched, and return to normal length (protective mechanism) |
| Contractility | the ability to shorten and produce tension |
| Conductivity | conduction of electrical excitation (via muscle stimulation) along membrane initiating contraction |
| Excitability | stimulation produces electrical charge |
| Fascia | sheet of fibrous tissue (collagen and some elastin); compartmentalizes groups of muscles |
| Endomysium | surrounds each muscle fiber or cell |
| Perimysium | binds muscle fascicles (fiber bundles) |
| Epimysium | surrounds whole muscle |
| Myofibrils | form muscle; composed of parallel protein microfilaments called myofilaments |
| Muscle Fibers | consist of myofibrils held together by sarcolemma |
| Sarcolemma | cell membrane of muscle cell; propagates nerve impulses |
| Sarcolemma | has transverse tubules that carry impulse from outer cell to inner cell |
| 2 types of myofilaments | actin and myosin: interact through crossbridges |
| Myofilaments | create alternating dark and light bands that give muscle fiber their striated appearance |
| Myofibrils | connect to tendon via endomysium |
| Force determinants | angle of orientation (pennation angle) between muscle fibers and tendon |
| Pennate | muscle fibers don't travel in direction of the reference (oblique); oblique orientation of the fibers allow for more fibers to fit into a given length of muscle (increasing cross-sectional area) |
| PCSA | standard measure used to approximate the number of fibers of a whole muscle |
| PCSA | area of a slice that passes through all of the fibers of a muscle; approximately equal to anatomical cross-sectional area in a parallel fiber muscle; considerably larger in a pennate muscle |
| Anatomical cross-section | area of a slice through the widest part of the muscle perpendicular to the muscle's length |
| Physiological cross-section | area of a slice that cuts through all of the fibers of the muscle |
| Longitudinal fibers | long fibers that run length of muscle, therefore can shorten more (large range of motion); high speed of contract, less force production than pennate |
| 3 types of penniform (pennate) | unipennate, bipennate, multipennate |
| Unipennate | off one side of the tendon; vastus lateralis |
| Bipennate | off both sides of tendon; Gastrocnemius, Rectus femoris |
| Multipennate | varieties of bipennate and unipennate; deltoid |
| Type I fibers | slow twitch, oxidative, small fibers; red (high myoglobin content); endurance athletes, resist fatigue |
| Type IIa fibers | intermediate fast twitch; oxidative-glycolytic |
| Type IIb fibers | fast twitch, glycolytic, large fibers; white; sprinters, jumpers; has more protein, fatigue rather fast |
| 3 ways muscle attaches to bone | directly, via a tendon, via an aponeurosis |
| Aponeurosis | sheath of fibrous tissue; flat tendon- ex) fascia around abdominal muscles, how they attach to back and pelvis |
| Coordination | the co-ordering of muscles to accomplish the task efficiently and effectively; regulated by nervous system |
| Prime mover | muscle(s) primarily responsible for a given movement or action in question; pectoralis major |
| Assistant mover | other muscles contributing to movement; trapezius helps to stabilize shoulder (helper muscles) |
| Agonist (movers) | muscles creating same joint movement; forearm curl (flexion phase)- brachialis and biceps brachii are primary agonists |
| Antagonist | muscle opposing agonist action; must first relax to permit movement then acts as a brake near end of movement |
| Triple burst pattern | muscle must first relax to permit movement then acts as a brake near end of movement |
| Stabilizer (fixator) | stops unwanted action at the fixed attachment (body part that does not move) of the muscle that is producing motion |
| Neutralizer | a muscle that can stop unwanted action at the mobile attachment |
| Co-contraction | simultaneous contraction of agonists/antagonists; usually antagonists to one another (biceps/triceps) |
| Contraction | whenever muscle fibers generate tension which may occur while the muscle is actually shortening, remaining the same length, or lengthening |
| Isometric | tension produced without visible change in joint angle; holding arms out to sides |
| Concentric | muscle visibly shortens while producing tension; up-phase of a sit-up |
| Eccentric | muscle visibly lengthens while producing tension; lowering phase of squat |
| Pre-stretch | quick lengthening of a muscle before contraction; generates greater force than contraction alone; utilizes elastic component of muscle |
| Fiber type I | slower pre-stretch best because of slow cross-bridging |
| Fiber type II | faster pre-stretch best because of fast cross-bridging; want to stimulate this type faster |
| Plyometrics | conditioning protocol that utilizes pre-stretching; single-leg bounds, depth jumps, stair hopping |
| One-jointed muscles | brachialis, pectoralis major |
| Two-jointed muscles (biarticulate) | save energy- gastronemius, hamstrings, biceps brachii |
| Resting length | when muscles are strongest; the mid length of a muscle between long and short |
| Concurrent movements | simultaneous flexion or extension- ex) hip and knee joints |
| Countercurrent movements | one muscle shortens rapidly at both joints; its antagonist lengthens correspondingly and thereby gains tension at both ends |
| Motor unit | group of muscles innervated by same motor neuron; from 4-2000 muscle fibers per motor unit |
| Action potential | signal to contract from motor neuron |
| Neuromuscular junction | also called end plate; where action potential from neuron meets muscle fiber |
| Conduction velocity | velocity at which action potential is propagated along membrane |
| Sarcomere | actin and myosin within a confined space |
Combine with other sets
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