A&P ch 10

unfused tetanus

when a skeletal muscle fiber is stimulated at a rate of 20-30 times per second it can only partially relax between stimuli; sustained but wavering contraction

anaerobic glycolysis

when muscle activity continues and the supply of creatine phosphate within the muscle fiber is depleted, glucose is catabolized to generate ATP

anaerobic glycolysis

yields 2 molecules of lactic acid and two molecules of ATP most of the lactic acid produced by this process diffuses out of the skeletal muscle fiber into the blood it produces less ATP than aerobic but the process is faster (2 min.)

Actin

Contractile protein that is the main component of thin filament; each actin molecule has a myosin-binding site where myosin head of thick filament binds during muscle contraction

Myosin

Contractile protein that makes up thick filaments; molecule consists of a tail and two myosin heads, which bind to myosin binding sites on actin molecules of thin filament during muscle contraction

Filaments

Contractile proteins within myofibrils that are two types Thick composed of myosin and thin composed of actin

Muscle fiber

Long cylindrical cell covered by endmysium and sarcolemma

Myofibril

Threadlike contractile elements within sarcoplasm of muscle fiber that extend entire length of fiber composed of filaments

Contractile protein

Proteins that generate force during muscle contractions

Regulatory protein

Proteins that help switch muscle contraction process on and off

Structural proteins

Proteins that keep thin and thick filaments of myofibrils in proper alignment

Tropomyosin

Regulatory protein that is a component of thin filament; when skeletal muscle fiver is relaxed it covers myosin binding sites on actin molecules, thereby preventing myosin from binding to actin

Troponin

Regulatory proteins that is a component of a thin filament When calcium ions bind to it it changed shape this conformational change moved tropomyosin away from myosin binding sites on actin molecules Muscle contraction begins as myosin binds to actin

Myomesin

Structural protein that forms m line of sarcomere binds to Titin molecules and connects adjacent thick filaments to one another

Dystrophin

Structural protein that links thin filaments of sarcomere to integral membrane proteins in sarcolemma which are attached in turn to proteins in connective tissue matrix that surrounds muscle fibers

Nebulin

Structural protein that wraps around entire length of each thin filament helps anchor thin filaments to z disc and regulates length of thin filaments during development

A-actinin

Structural proteins of z discs that attached to actin molecules of thin filaments and to Titin molecules

Titin

Structural proteins that connect z disc to m line of sarcomere Helps stabilize thick filament position Accounts for much of elasticity

twitch contraction

brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron

latent period

brief delay occurs between application of the stimulus and the beginning of contraction

contraction period

calcium binds to troponin myosin binding sites on actin are exposed and cross bridges form

relaxation period

calcium is actively transported back into the SR myosin binding sites are covered by tropomyosin, myosin heads detach from actin and tension in the muscle fiber decreases

oxygen debt ( recovery oxygen uptake )

added oxygen over and above the resting oxygen consumption that is taken into the body after exercise

multiunit smooth muscle tissue

consists of individual fibers each with its own motor neuron terminals and with few gap junctions between neighboring fibers walls of large arteries, lungs, arrector pilli and muscles of the iris

motor unit

consists of somatic motor neuron plus all of the skeletal muscle fibers it stimulates even though each skeletal muscle fiber has only a single neuromuscular junction the axon of a somatic motor neuron branches out and forms neuromuscular junctions with many different muscle fibers

glycolysis

quickly breakdown each glucose molecule into to molecules of pyruvic acid; occurs in the cytosol and produces a net gain of two molecules of ATP it does not require oxygen

an energy rich molecule that is found in muscle fibers and is synthesized by most of the extra ATP; also 3-6times more plentiful than ATP in the sarcoplasm of relaxed , muscle fiber

creatine phosphate

wave summation

stimuli arriving at different times cause larger contractions

flaccid

flabby

visceral single unit (Spartan) smooth muscle

found in the skin and in tubular arrangements that form walls function as a unit; autorhythmic; fibers connect to one another though gap junctions

during anaerobic glycolysis the pyruvic acid ____ rather than go to the mitochondria

generated from glycolysis is converted to lactic acid

aerobic respiration

if sufficient oxygen is present the pyruvic acid formed by glycolysis enters the mitochondria where it undergoes _______ a series of oxygen requiring reactions that produce ATP carbon dioxide water and heat; it is slower but produces more ATP

fused tetanus

sustained contraction in which individual twitches cannot be detected

fast glycolytic fibers

low myoglobin content relatively few blood capillaries and few mitochondria and appear white in color contain large amounts of glycogen and generate ATP mainly by glycolysis contract strongly and quickly powerlifting fatigue quickly

eccentric contraction

muscle lengthens and increases angle

concentric contraction

muscle shortens and reduces angle

muscular tissue has two sources of oxygen:

oxygen that diffuses into muscle fibers from the blood and oxygen released by myoglobin within muscle fibers they are both oxygen binding proteins they bind it when it is plentiful and release it when it is scarce

refractory period

the period of lost excitability is a characteristic of all muscle and nerve cells

isotonic contraction

the tension (force of contraction) developed in the muscle remains almost constant while the muscle changes its length

isometric contraction

the tension generated is not enough to exceed the resistance of the object to be moved and the muscle does not change its length

fast oxidative glycolytic fibers

typically the largest fibers; contain large amounts of myoglobin and many blood capillaries they also have dark red appearance generate considerable ATP through aerobic respiration they can also generate ATP through anaerobic glycolysis they are fast because the ATPase in their myosin heads hydrolyzes AtP three to five times faster than the myosin ATPase in SO fibers

Fascicle

Bundle of muscle fibers wrapped in perimysium

slow oxidative fibers

appear dark red because they contain large amounts of myoglobin and many blood capillaries contain mitochondria and generate ATP through aerobic respiration