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muscle fibers

skeletal and smooth muscle cells; elongated cells;






subject to conscious control


no conscious control, automatic


obvious stripes in muscles

"bundle-within-a-bundle" design

muscle, fasicle, muscle fiber, myofibril, sarcomere, myofilament


surround muscle fibers; composed of areolar and reticular tissue fibers


surround the fascicles; composed of fibrous connective tissue


surrounds the whole muscle; composed of dense irregular tissue


muscle attachment to the movable bone


muscle attachment at the immovable/less movable bone

direct muscle attachment

epimysium fused directly to the periosteum of obone

indirect muscle attachment

muscle is connected to a tendon


rope-like muscle attachment


sheet-like muscle attachment

skeletal muscle fibers

long cylindrical cell with multiple oval nuclei arranged just beneath the sarcolemma


plasma membrane of a muscle cell


cytoplasm of a muscle cell


red pigment similar to hemoglobin that stores oxygen


rod like fibers that run the length of the cell; contain contractile elements; 80% of cellular volume; made up of myofilaments


region of a myofibril between two successive Z discs

thick filaments

composed of myosin


rod-like tail with two globular heads

cross bridges

globular heads of myosin line the thick and thin elements together; allows contraction

thin filaments

composed of actin; contain tropomyosin (to stiffen) and troponin


bears active sites for myosin during contraction

Sarcoplasmic Reticulum

comparable to the smooth endoplasmic reticulum; regulates intracellular levels of ionic calcium; stores and releases calcium at the correct times

T tubules

elongated tube penetrating into the cell from the sarcolemma; the "telegraph system"; ensures every myofibril contracts at the same time

sliding filament model of muscle contractioin

thin filaments are pulled toward the sarcomere centers by cross bridge activity of the thick filament

action potential

electrical current/ nerve impulse.

neuromuscular junction

location where the terminal portion of a motor neuron axon meets a muscle cell membrane

synaptic cleft

the space between the nerve and muscle fiber

motor unit

one motor neuron and all the muscle cells it innervates

muscle twitch

response of a muscle to a single action potential of its motor neuron

latent phase

first few milliseconds after stimulation

contraction phase

cross bridge actively forms and muscle shortens


calcium is reabsorbed into the sarcoplasmic reticulum; muscle tension decreases to zero

incomplete tetanus

more rapidly delivered; quivering contraction

complete tetanus

if stimuli are given quickly enough, smooth sustained contraction occurs (tetanus)

recruitment (staircase effect)

increased contraction in response to multiple stimuli of the same strength; increases availability of calcium in sarcoplasm; "warm-up" period for athletes

muscle tone

constant slightly contracted state of all muscles that does not produce movement; keeps the muscles firm, healthy and ready to respond

isotonic contraction

occur at a joint; decrease muscle length, moves the load

isometric contraction

increases muscle tension; load is not moved

roles of ATP

1. transfers energy to myosin cross bridge to energize the power stroke; 2. disconnects the myosin cross bridge from the actin binding site; 3. fuels the pump that actively transports calcium ions to the sarcoplasmic reticulum

regeneration of ATP

1. interaction of ADP with creatine phosphate; 2. stored glycogen via anaerobic pathways, aka glycolysis; 3. aerobic respiration

aerobic endurance

length of time a muscle can contract by glycolysis

anaerobic threshold

point that muscle metabolism converts to anaerobic glycolysis

muscle fatigue

physiological inability to contract due to shortage of ATP; results from ionic imbalance, lactic acid and lack of ATP


total lack of ATP; cramps

oxygen debt

the amount of oxygen required after physical exercise for restorative processes

optimal length for muscle fibers

80-120% of their normal resting length

muscle fiber types

1. slow oxidative; 2. fast oxidative; 3. fast glycolic

resistance exercise

lifting weights; isometric excercise; promotes strength not stamina


cell that nearly all muscle tissues develop from

muscle mass

36% of body for women; 42% of body for men; main difference is levels of testosterone

Muscular Dystrophy

muscle destroying disease

Duchenne Muscular Dystrophy

most common form of muscular dystrophy; inherited sex-linked disease carried by females and normally expressed in males; diagnosed between the ages of 2-10; victims become clumsy and fall frequently as their muscles fail; progresses from the extremeties upward and victims die of repiratory failure in their 20s; there is no cure


sudden, involuntary twitch; possibly due to chemical imbalances


stretching or tearing of the ligaments


commonly called a pulled muscle; excessive stretching and possible tear of muscle due to overuse/ abuse

tetanus (bacterial)

acute infectious disease resulting in painful spasms of skeletal muscles; eventually results in lock jaw and respiratory failure


muscle pain resulting from any muscle disorder


disease of the muscle


treatment of sprains and strains; stands for Rest Ice Compression and Elevation


inflammation of muscle tissue

rigor mortis

muscular stiffening that begins 2 to 4 hours after death and last for about 4 days

prime mover

provides major force in movement


also called prime mover; provides major force in movement


oppose/reverse a particular movement; produce smooth, coordinated and precise movements with synegists


add extra force to the prime mover; reduce undesirable movements; also called fixators when they immobilize a bone or muscles origin

parallel fascicles

run parallel with bone; straplike

pennate fascicles

short, attach obliquely to a central tendon; look like a feather; ex. extensor digitorum

convergent fascicles

broad origin; fascicles converge toward a single tendon; triangular shape; pectoralis major

circular fascicles

concentric rings; body openings; sphincters and orbicularis oris

fusiform fascicles

spindle shaped with a "belly"; biceps brachii


body openings controlled by contractions


rigid bar that moves on a fixed point when force is applied; bones


fixed point in a lever system; joints


applied force; muscle contraction


resistance; bone, tissue and everything else that needs to be moved

first-class lever

load-fulcrum-effort; raising head off of chest

second-class lever

fulcrum-load-effort; standing on tiptoe.

third-class lever

load-effort-fulcrum; flexion of the biceps brachii, doing a curl

Valsalva Maneuver

abdominals contract with the diaphragm and the glottis is closed to create internal pressure; promotes urination, defecation, childbirth, vomitting, screaming, sneezing, burping, and nose blowing

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