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217 Cards in this Set
- Front
- Back
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maximus |
largest |
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minimus |
smallest |
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3 muscle tissues |
skeletal, caridac, smooth - all exert excitability |
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plasma membranes can change their electrical states (from polarized to depolarized) and send electrical wave called action potential on entire length of membrane |
excitability |
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skeletal muscle completely depends on nervous system to |
work properly |
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these respond to nervous system and hormones and local stimuli |
cardiac and smooth muscle |
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muscles begin contracting (shortening) when |
actin(protein) is pulled by myosin (protein) - occurs in striated muscle (skeletal and cardiac) after bnding sites on actin are exposed due to Ca ions and proteins (troponin and tropomysoin) that shield actin binding sites - all muscles require atp to continue contracting - all relax when Ca++ is removed and actin binding sites are re shielded |
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calcium and muscles |
- protect striated muscle actin binding sites and required for contraction of smooth muscle |
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cal for contraction of smooth muscle |
- ca++ acivates enzyme which activate myosin heads - and myosin binding site is exposed for interaction |
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muscle return to original length when relaxed is this quality - muscle recoil to original length due to elastic fibers is this quality |
elasticity |
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muscle stretching and extending is this quality |
extstensibility |
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muscle tissue pulling on its attachment points and shorten with force is this quality |
contractility |
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cytoplasm of individual muscle cells (fibers) of skeletal and cardiac muscle has |
- actin and myosin regularly arranged - creates striations |
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- multinucleated fibers |
skeletal muscle |
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- each have one or two nuclei - physically and electrically connected to each other so contraction occurs as one unit (syncytinum) |
cardiac muscle |
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- actin and myosin not arranged regularly - single nucleus - non striated - regulates blood pressure (circulatory system) and moving materials through the body |
smooth muscles |
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joints can vecome misaligned or dislocated by |
pulling of associated bones - muscles help keep joints stable |
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skeletal muscles located at |
body at openings of internal tracts to control movement of carious substances - allow swallowing, urination, defecation to be voluntary - protect internal organs (abdominopelvic) by acting as external varrier and supporting weight of organs |
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skeletal muscles and homeostasis |
- generates heat - muscle contraction produces heat |
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skeletal muscle organ consists of these integrated tissues |
- skeletal muscle fibers - blood vessels - nerve fibers - each has 3 layers of connective tissue (called mysia) = this encloses it and provides structure to the muscle, compartamentalizes muscle fibers within muscle - wrapped in epimysium (dense, irregular connective tissue) = allows contraction and move powerfully and maintain structure, and seperates muscle form other tissues and organs |
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muscle fibers organized into individual bundles |
- fascile - organized by perimysium (ct) |
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inside fascile muscle fiber is encased in thin ct layer of collagen and reticular fibers called |
endomysium - contains extracellular fluid and nutrients to support muscle fiber - supplied via blood to muscle tissue |
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in skeletal muscles that work with tendons to pull on bones, collagen in mysia |
intertwines with colalgen of tendon - other end of tendon fuses with periosteum coating the bone |
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tension by contraction of muscle fibers is |
transferred through mysia to tendon and then to periosteum to pull on bone for movement |
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mysia may fuse with broad tendon like sheet called |
apopneurosis (fascia) - ct between skin and bones - ex. latissimus dorsie msucles ct fuse to is apopneurosis |
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- vascular - axon branch of somatic motor neuron, signals fiber to contract - only way to functionally contract is through singlaing from nervous system |
skeletal muscle |
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- long , cylindrical - up to 100mm diameter and 30 cm length in sartorius of upper leg - myoblasts with own nucleuses fuse to other myoblasts to form multinucleated fibers - multiple copies of genes allowing production of large amounts of proteins and enzymes needed for muscle contraction |
skeletal muscle fibers |
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plasma membrane of muscle fibers is |
sarcolemma |
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cytoplasm of muscle fibers is |
sarcoplasm |
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specialized smooth endoplasmic reticulum in muscle fibers is - stores and releases and retreives calcium ions (Ca++) |
sarcoplasmic reticulum |
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functional unit of a skeletal muscle fiber is the |
sacromere - highly organized arrangement of contractile myofilaments actin(thin) and myosin(thick) and support proteins |
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actin |
thin myofilament |
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striated appearance of skeletal msucle fibers due to |
arrangement of myoflimaents of actin and myosin in sequential order from one end of muscle fiber to other
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microfilaments of myofilaments of actin and myosin and regulatory proteins (troponin and tropomyosin) is called |
sacromere |
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functional unit of msucle fiber |
sarcomere - bunled in myofibril that runs length of fiber and attaches to the sarcolemma at end - as myofibrils contract, entire msucle cell contracts |
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myofibrils size |
1.2 mm in diameter - so hundreds to thousands can be found inside 1 muscle fiber - 2 mm in length |
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z disc |
- actin myofilaments anchored - |
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actina nd tropnin-propomyosin complex (toward sacromere from z discs) are |
thinner than myosin so called thin filament of sarcomere |
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- heads project from center of sarcomere toward but not all the way to z discs - have more mass - thicker |
thick filament of sarcomere |
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site where motor neurons terminal meets muscle fiber - where fibers first respond to signaling by the motor neuron - ever skeletal muscle fiber in every skeletal muscle is innervated by motor neuron at this - excitation signals from neuron are only way to functinoally activate fiber to contract |
neuromuscular junction MMJ |
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all living cells have this |
membrane potentials or electrical gradients across tehir membranes |
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membrane ptoential or electrical gradient |
- inside usually -60 to -90mV - generate electrical signals - control movement of charged particles (ions) across membranes through ion channels (proteins) to create electrical currents that form basis for neural signaling and muscle contraction |
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neurons and skeletal muscle cells are |
electrically excitable (able to generate action potentials) |
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action potential |
type of electrical singal that can travel along a cell membrane as a wave - allows signal to be transmitted quick over long distances |
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excitation contraction coupling |
- skeletal msucle fiber to contract = membrane must be excited - action potential along sarcolemma as wave is coupled to contraction through release of calcium ions from SR - Ca++ interacts with proteins making the actin binding sites available for attachment by myosin heads - myosin then pulls the actin filaments toward teh center shortening the muscle fiber |
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in skeletal msucle the excitation- contraction coupling begins with |
signals from somatic motor division of the nervous system
- always from nervous system that originate in spinal cord - brainstem for activation of skeltal msucles of face, head, and neck
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at NMJ the axon terminal releases |
ACh |
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motor end plate is |
location of ACh receptors in muscle fiber sarcolemma |
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axons |
- neurons long proceses that transmit action potentials long distance |
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axons of multiple neurons bundle together to form |
nerves |
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signaling begins when |
neuronal action potential travels along the axon of a motor neuron and then individual branches to terminate at the NMJ - at NMJ axon terminal releases neurotransmitter called acetylcholine ACh - ACh diffuses across synaptic cleft and binds to ACh receptors in motor end plate of sarcolemma on othe side of the synapse - once ACh binds, channel in ACh receptor opens and + ions can pass through into muscle fiber, causing it to depolarize (membrane potential of muscle fiber becomes less negative) - as membrane depolarizes, voltage gated sodium channels are opened , sodium ions enter the muscle fiber and action potential rapidly spreads along entire membrane to initiate excitation contraction coupling |
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ACh |
acetylcholine - neurotransmitter at NMJ that is apart of excitation contraction coupling |
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ACh in synaptic cleft is degraded by enzyme |
acetylcholinesterase AChE - so ACh cannot rebind to receptor and reopen its channel, which would cause unwanted extended muscle excitation and contraction |
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- triggers release of ca++ from storage in cells SR - action potential reaches membrane of SR by invaginations in sarcolemma (T-tubules) these ensure membrane can get close to SR in sarcoplams |
sarcolemma excitation portion |
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- action potential reaches membrane of SR by invaginations in sarcolemma |
(T-tubules) these ensure membrane can get close to SR in sarcoplams - permit conduction of electrical impulses |
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t tubule with membranes of SR on either side is |
triad - surrounds myofibril which has actin and myosin |
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SR function |
- regulate intracellular levels of calcium |
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these carry the action potential into the interior of the cell which triggers the opening of calcium channels in the membrane of the adjacent SR causing ca++ to diffuse out of sr and into sarcoplasms |
t tubules |
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_____ in sarcoplasm initiates contraction of the muscle fiber by its contractile units or sacromeres |
ca++ |
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events that result in contraction of individual muscle fiber |
1. ACh neurotransmitter from motor neuron innervating the fiber 2. membrane of fiber will depolarize as Na+ enter, triggering action potential that spreads to rest of membrane and t tubules to depolarize 3. this triggers release of Ca++ from storage in sarcoplasmic reticulum 4. Ca++ initiates contraction, sustained by atp |
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as long as ____ the muscle fiber will continue to shorten to an anatomical limit |
Ca++ ions remain in sarcoplams to bind to troponin (keeping actin binding sites open) and atp is available to pull actin by myosin |
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A cross-bridge forms between actin and the myosin heads triggering |
contraction. |
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As long as Ca++ ions remain in the sarcoplasm to bind to troponin, and as long as ATP is available, the muscle fiber will continue to |
shorten. |
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muscle contraction stops when |
signaling form motor enuron ends - which repolarizes in sarcolemma and t tubules, and closes voltage gated calcium channels in SR - Ca++ pumped back to SR and tropomyosin recover binding sites on actin strands - when runs out of atp |
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when thick and thin filament interaction seperates or relaxes |
muscle lengthens and relaxes - calcium is resorbed, and begins relaxation cycle, atp is required |
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Ca++ ions are pumped back into the SR, which causes |
the tropomyosin to reshield the binding sites on the actin strands. A muscle may also stop contracting when it runs out of ATP and becomes fatigued. |
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muscle fiber shortening occur in |
fibers sarcomeres |
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contraction of striated muscle fiber occurs as |
sarcomeres within myofibrils shorten as myosin head pull on actin filaments |
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- region where thick and thin filaments overlap - dense - little space between filaments - where filament movement starts |
thin anchored by z discs, do not extend completely into central region, at base is m line |
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myofibril is composed of |
many sarcomeres running length - myofibrils and muscle cells contract as sarcomeres contract |
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skeletal muscle fiber contracts as |
thin filaments are pulled then slide past thick filaments within sarcomeres - slidig filament model of muscle contraction - can only occur when myosin binding sites on teh actin filaments are exposed by a series of steps that being wit ca++ entry into sarcoplasm |
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sliding filament model of muscle contraction |
When a sarcomere contracts, the Z lines move closer together, and the I band becomes smaller. The A band stays the same width. At full contraction, the thin and thick filaments overlap. |
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When a sarcomere contracts, the Z lines move |
closer together, |
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When a sarcomere contracts, the I band |
becomes smaller. |
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When a sarcomere contracts the A band |
stays the same width. |
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At full contraction, |
the thin and thick filaments overlap. |
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- protein that surrounds actin filament and covers myosing binding sites to prevent actin from binding to myosin |
tropomyosin - binds to troponin to form troponin-tropomyosin complex to prevent myosin heads from binding to active sites on actin microfilaments |
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troponin-tropomyosin complex |
- prevent myosin heads from binding to active sites on actin microfilaments - binding site for ca++ ions |
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to initiate muscle contraction tropomyosin has to |
expose myosin binding site on an actin filament to allow bridge formation between actin and myosin |
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The Sliding Filament Model of Muscle Contraction steps |
1. ca++ bind to troponin so tropomyosin can slide away from binding sites on actin strands, allows myosin heads to bind to exposed binding sites and form bridges 2. thin filaments pulled by myosin heads to slide past thick filaments toward center of sarcomere 3. recocked with atp |
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cross bridge cycle |
thin filaments slide past thick filaments during muscle contraction - myosin pulls actin at binding sites, detach, recock, attach to more binding sites, pull, detach , recock - requires atp and action of myosin heads in sarcomeres requires atp |
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Skeletal Muscle Contraction |
(a) The active site on actin is exposed as calcium binds to troponin. (b) The myosin head is attracted to actin, and myosin binds actin at its actin-binding site, forming the cross-bridge. (c) During the power stroke, the phosphate generated in the previous contraction cycle is released. This results in the myosin head pivoting toward the center of the sarcomere, after which the attached ADP and phosphate group are released. (d) A new molecule of ATP attaches to the myosin head, causing the cross-bridge to detach. (e) The myosin head hydrolyzes ATP to ADP and phosphate, which returns the myosin to the cocked position. |
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cross bridge formation occurs when |
myosin head attaches to actin whil adp and inorganic phosphate are still bound to myosin - pi is released causing myosin to form stronger attachment to actin - myosin head moves toward m line pulling actin with it , filaments move 10nm toward m line (called power stroke) - in absence of atp myosin head will not detach from actin |
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- movement of thin filament - actin pulled 10nm toward m line |
power stroke |
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atp biding causes myosin head to |
detach from actin - after atp is converted to adp and pi by intrinsic ATPase of myosin - energy released changes angle of myosin head into cocked position ( for further movement) |
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when mysoin head is cocked |
myosin is in high energy configuration - expended through power stroke - at end of power stroke myosin head is in low energy position, adp is released, cross bridge is still in place and actin and myosin are bound together - as long as atp is available it attaches to myosing, cross bridge can occur and msucle contractions continue |
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each thick filament is |
300 myosin molecules with multiple heads and many bross bridges forming and breaking |
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sacromeres in |
myofibril |
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myofibrils in |
muscle fiber |
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muscle fibers in |
skeletal muscle |
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rigor mortis after someone dies is |
loss of atp - myosin heads detach from actin binding sites so cross bridges stay in place causing rigidity in skeletal muscles |
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atp and muscle conraction |
- supplies energy - energy for active transport of ca++ pumps in SR - lil atp stored in uscle |
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3 ways atp is regenerated |
- creatine phosphate metabolism - anaerobic glycolysis - fermentation and aerobic respiration |
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creatine phosphate |
- molecule that can store energy in phosphate bonds - in resting muscle excess atp energy is transfered to creatine, producing adp and creatine phosphate - quickly creates more atp - creatine phosphate transfers its phosphate back to adp to form atp with creatine - catalyzed by enzyme creatine kinase - first seconds of muscle contraction - 15 seconds worth of energy |
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Muscle Metabolism |
(a) Some ATP is stored in a resting muscle. As contraction starts, it is used up in seconds. More ATP is generated from creatine phosphate for about 15 seconds. (b) Each glucose molecule produces two ATP and two molecules of pyruvic acid, which can be used in aerobic respiration or converted to lactic acid. If oxygen is not available, pyruvic acid is converted to lactic acid, which may contribute to muscle fatigue. This occurs during strenuous exercise when high amounts of energy are needed but oxygen cannot be sufficiently delivered to muscle. (c) Aerobic respiration is the breakdown of glucose in the presence of oxygen (O2) to produce carbon dioxide, water, and ATP. Approximately 95 percent of the ATP required for resting or moderately active muscles is provided by aerobic respiration, which takes place in mitochondria. |
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atp by creatine phosphate is depleted muscles turn to |
glycolysis as atp source |
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anaerobic process that breaks down glucose to produce atp - cannot generate atp as quickly as creatine phosphate - 1 minute - short burst of high intensity output |
glycolysis |
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breakdown of one glucose molecule produces |
2 atp molecules and 2 pyruvic acid molecules which can be used in aerobic respiration or when oxygen is low (converted to lactic acid) |
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- may contribute to muscle fatigue - if oxygen not available pyruvic acid produced by glycolysis is converted to - this conversion allows for recycling of enzyme NAD+ from NADH - occurs when high amounts of energy needed but oxygen cannot be sufficiently delivered to muscle (intense exercise) |
lactic acid |
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breakdown of glucose or other nutrients in presence of oxygen to produce co2, water, and atp - takes place in mitochondria - inputs= glucose, pyruvic acid, fatty acids - 36 atps produced per glucose |
aerobic respiration |
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___% of atp required fro resting or moderatly active muscles is provided by aerobic respiration |
95% |
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muscles store small amount of oxygen in proteins called |
myoglobin allowing for more efficient muscle contractions and less fatigue - muscle training increases efficiency of circulatory system so oxygen can be supplied to muscles for long time |
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when muscle can no longer contract in response to signals from nervous system |
muscle fatigue - low atp, intense muscle output, lactic acid buildup lowering ph affecting enzyme and protein activity, imbalances in na+ and k+ as result of membrane depolaraization may disrupt ca++ out of sr - long sustainded exercise may damage sr and sarcolema impairing ca++ regulation |
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intense muscle activity results in |
oxygen debt - amount of oxygen needed to compensate for atp produced wo oxygen during muscle contraction - until oxygen debt has been met, oxygen intake is elevated |
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oxygen is required to |
restore atp and creatine phosphate levels, convert lactic acid to pyruvic acid, in liver convert lactic acid into glucose or glycogen |
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relaxing skeletal muscle fibers
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- begins with motor neuron - stop release of ACh into synapse of NMJ - muscle fiber repolarize and close gates in sr where ca++ was being released - atp pumps will move ca++ ot of sarcoplasm back into sr - muscle fibers lose tension and relaxes |
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# of skeletal muscle fibers |
genetically determined and does not change |
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muscle strength related to |
amount of myofibrils and sarcomeres within each fiber - hormones and stress can increase production of sarcomeres and myofibrils - hypertrophy = increased mass and bulk in skeletal muscle |
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atrophy |
- decreased use of skeletal muscles - number of sarcomeres and myofibrils dissapear (but not number of muscle fibers) - casted limb - polio show atrophied muscles |
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duchenne muscular dystrophy DMD |
- progressive weakening of skeletal muscles - muscular dystrophy - caused by lack of protein dystrophin (helps thin filaments of myofibrils bind to sarcolemma) - inherited caused by abnormal x chromosome - males - usually diagnosed in early childhood - difficulty with balance and motion, inability to walk - ultimately causes death to respiratory failure, expected lifespan to 20s - healthy myoblasts potential treatment - boost production of utrophin |
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to move a load sarcomeres in muscle fibers of skeletal muscle |
shorten - force generated by contraction of muscle (shortening of sacromeres) called muscle tension |
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force generated by contraction of muscle (shortening of sacromeres) |
muscle tension |
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2 skeletal muscle contractions |
isotonic and isometric contractions |
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- tension in the muscle stays constant - load moved as length of muscle shortens - concentric and eccentric |
isotonic contractions of skeletal muscle |
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concentric isotonic contactions in skeletal muscle |
- muscle shortening to move a load - myosin heads pull the actin |
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eccentric isotonic contactions in skeletal muscle |
- muscle tension diminishes and muscle lengthens - cross bridges being activated decreases - movement and balance of body |
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isometric contactions in skeletal muscle |
- muscle produes tension without changing the angle of a skeletal joint - sacromere shortening and increasing muscle tension - do not move a load - maintain posture and maintain bone and joint stability |
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muscle contracts - less than 90 degree angle |
concentric contraction |
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muscle elongates - more than 90 degree angle |
eccentric contraction |
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muscle contracts - no movement |
isometric contraction |
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During isotonic contractions, muscle length changes to move a load. During isometric contractions, muscle length does not change because the load exceeds the tension the muscle can generate. |
ya |
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neural control regulates |
concentric, eccentric, isometric contractions, mscle fiber recruitment, muscle tone - role of motor units |
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every skeletal muscle fiber must be |
innervated by axon terminal of motor neuron in order to contract - each fiber only 1 motor neuron |
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group of muscle fibers in a muscle innervated by a single motor neuron is |
motor unit - size variable - small = fine control (eye muscles, fingers, thumb) - large = gross movements (thigh muscles, back muscles) |
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increasing activation of motor units pruducing increase in muscle contraction |
recruitment - more motor units = muscle contraction grows stronger - allows for different contractile forces |
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when skeletal muscle fiber contracts |
- myosin head attaches to actin to form bridges with thin filaments sliding over thick filaments as heads pull actin, resulting in sacromere shortening, creating tension of muscle contraction |
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cross bridges can only occur where |
thin and thick filaments already overlap |
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length tension relationship |
length of sarcomere has influence on force generated when sarcomere shortens |
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length of sarcomere to produce maximal tnesion is |
80 percent to 120 ercent of its resting length - 100 percent state where medial ddges of thin filaments are most medial myosin head of thick filaments, this maximizes overlap of actin binding sites and myosin heads - if past 120 filaments do not overlap sufficiently, no cross bridges formed, and less tension is produced - if less than 80 percent, zone of overlap is reduced and h zone is smaller, thin filaments stick out , tension diminished |
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Sarcomeres produce maximal tension when thick and thin filaments overlap between about |
80 percent to 120 percent. |
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twitch |
isolated contraction - single action potention from motor neuron producing single contraction in muscle fibers of its motor unit - miliseconds - measuresd by myogram - 3 phases |
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myogram |
instrument that measures amount of tension produced over time - measures twitches |
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twitch phases |
1. latent period = action potential is being propagated along sarcolemma and ca++ are released from sr; excitationa dn contraction coupled but no contraction yet 2. contraction phase = ca++ in sarcoplasm bound to troponin, tropomyosin shifts away from actin binding sites, cross bridges form, sarcomeres actively shortening to point of peak tension 3. relaxation phase = tension decreases as contraction stops; ca++ pumped out of sarcoplasm into sr, cross bridge cycling stops |
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A single muscle twitch has |
a latent period, a contraction phase when tension increases, and a relaxation phase when tension decreases. During the latent period, the action potential is being propagated along the sarcolemma. During the contraction phase, Ca++ ions in the sarcoplasm bind to troponin, tropomyosin moves from actin-binding sites, cross-bridges form, and sarcomeres shorten. During the relaxation phase, tension decreases as Ca++ ions are pumped out of the sarcoplasm and cross-bridge cycling stops. |
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single twitch |
does not produce significant muscle activity in living body |
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graded muscle response |
frequency of action potentials (nerve impulses) from motor neuron and umber of motor neurons transmitting action potentials both affect tension produced in skeletal muscle |
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wave summation |
- excitation-contraction coupling effects of successive motor neuron signaling is summoned or added together - more the stronger - second stimulus triggers release of more ca++ ions |
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(a) The excitation-contraction coupling effects of successive motor neuron signaling is added together which is referred to as wave summation. The bottom of each wave, the end of the relaxation phase, represents the point of stimulus. |
wave summation |
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(b) When the stimulus frequency is so high that the relaxation phase disappears completely, the contractions become continuous; this is called - concentration of ca++ in sarcoplasm allows all sarcomeres to form cross bridges and shorten so contraction can continue uninterrupted until muscle fatigues |
tetanus. |
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when muscle has been dormant and then activated to contract |
initial contraactions generate 1/2 force of later contractions |
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treppe |
- muscle contractions become more efficient - staircase effect |
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When muscle tension increases in a graded manner that looks like a set of stairs, it is called _____. The bottom of each wave represents the point of stimulus. - results from higher concentration of ca++ in sarcoplasm rsulting from stream of motor neurn signals, maintained by atp |
treppe |
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muscle tone allows |
joints to be stable and to maintain posture |
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hypotonia or atrophy |
absence of low level contractions that lead to muscle tone - result from damage to parts of central nervous system like cerebellum, loss of innervations lie polio - flaccid appearance |
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hypertonia |
- hyperreflexia - damage to upper motor neurons in central nervous system - muscle rigidity(parkinsons) - spacticity, limb snap back from passive stretching (strokes) |
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3 skeletal muscle fibers |
- slow oxidative - fast oxidative - fasty glycolytic |
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- fibers contract slow and use aerobic respiration to produce atp - many mitochondria - small diameter - not alot of tension so not used for powerful movments - myoglobin gives red color - sustain muscle activity without fatiguing for long periods of time - maintain posture, produce isometric contractions, stabilize bones and joints, make small movements happen often |
slow oxidative muscle fiber |
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- fiber fast contractions and primarily use aerobic respiration but may switch to anaerobic respiration (glycolysis) - can fatigue more quickly than so - intermediate fibers bc posses characteristics between fast and slow fibers - do not posses significant myoglobin, lighter color - movements, walking |
fast oxidative muscle fiber |
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- fibers that have fast contractions and primarily use anaerobic glycolysis - fatigue quickest - largest diameter - high amounts of glycogen - lil # of mitochondria - lil myoglobin, white color - produce rapid, forceful contractions to make quick movements |
fast glycolytic muscle fiber |
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speed of contraction in muscle fibers is depedent on |
how quick myosins atpase hydrolyzes atp to produce cross bridge action - fast 2x as fast (pulls thin filaments toward center of sacromere at faster rate) |
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oxidative |
- fiber primarily produces atp through aerobic pathway - these contain more mitochondria - SO |
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hypertrophy |
structural proteins added to muscle fibers - cell diameter increases |
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when structural proteins are lost and muscle mass decreases |
atrophy |
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age related muscle atrophy is |
sarcopenia |
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slow fibers used in |
endurance exercise - aerobic - more mitochnodria - myoglobin(in sarcoplasma and acts as oxygen storage for mitochondria) increase |
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endurance exercise |
- formation of more capillary ntwords around fiber (angiogensis) to supply oxygen and remove metabolic waste - muscle mass does not increase greately do allow diffusion of nutrients and gas |
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endurance athletes benefit from |
larger proportion of so fibers - can result in stress fractures, joint and tendon inflammation - large number of so fibers and few fo and fg - long distance runners |
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resistance exercise |
- large amounts of FG fibers to produce short, powerful movements that are not repeated - increases formation of myofibrils, increasing thickness of uscle fibers - causes hypertrophy or enlargement of muscles - consume protein bc this muscular enlargement is thorugh addition of structural proteins - increases development of connective tissue, adding to overall mass of the muscle - tendons become stronger - |
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body builders have high |
fb fibers |
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performance enhancing substances |
- anabolic steroids = testosterone, inreases muscle mass - erythropoietin = hormone produced in kidneys, triggers production of rbcs - human growth hormone = promote healing of muscle and other tissues - creatine = atp to muscles |
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anabolic steroids side affects |
infertility, agressive behavior, cvd, brain cancer |
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sarcopenia |
irreversible - muscle fibers die and are replaced by ct and adipose tissue - greater numbers of so fibers - less numbers of fg fibers - reduction in size of motor units |
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cardiac muscle tissue |
- only in heart - pump blood into vessels of circulatory system - striated - organized into sarcomeres - long action potentials in fibers, has sustained depolarization plateua produced by ca++ entry through voltage gated calcium channels in sarcolemma and provide for longer contraction - ca++ comes from outside the cell rather than the SR - shorter and only one nucleus in central region of cell - many mitochondria and myoglobin - primarily aerobic - branched - has intercalated discs which connect cells and allows cells to contract in wave like pattern |
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______ allows the cardiac muscle cells to contract in a wave-like pattern so that the heart can work as a pump. - part of sacrolemma - gap junctions and desmosomes |
An intercalated disc |
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gap junction |
- forms channels between adjacent cardiace muscle fibers that allow depolrizing current produced by cations to flow from one cardiac muscle cell to the next (electric coupling) which allows quick transmission of action potentials and unity contraction |
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network of electrically connected cardiac muscle cells creates |
functional unit of contraction called syncytium |
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- cell structure that anchors the ends of cardiac muscle fibers together so cells do not pull apart during contraction |
desmosome |
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Intercalated discs are |
part of the cardiac muscle sarcolemma and they contain gap junctions and desmosomes. |
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contractions of heartbeats are controlled by |
pacemaker cells - responds to signals from autonomic nervous system and hormones |
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wave of contraction that allows heart to work as a unit |
functional syncytium - begins with pacemaker cells - autorhythmicity = able to depolrize and fire action potential on their own , determine heart rate |
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- no striations - present in walls of hollow organs - urinary bladder, uterus, stomach, intestines, passageways like arteries, veins, respiratory, urinary, circulatory, and reproductive tracts - eyes (changes size of iris) - skin (causes hair to stand erect in response to cold or fear) - spindle shaped - uninucleated - produce their own ct, endomysium - have actin and myosin proteins, and thick and thin filaments - do not have sarcomeres - ca ions supplied by sr in fibers and by sequestration from extracellular fluid through calveoli |
smooth muscle tissue |
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analogous to z discs of skeletl and cardiac muscle fibers and is fastened to sarcolemma |
dense body - in smooth tissue fibers |
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these do not contain troponin but instead have regulatory protein calmodulin |
smooth muscle cells |
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in smooth muscle fiber |
- external ca++ pass through sarcolemma, and ca++ released from SR bind to calmodulin - the ca++ calmodulin complex activates enzyme myosin(light chain) kinase, which activtes myosin heads by phophorylating them(atp to adp and pi) |
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latch bridges |
- bridges between myosin heads and actin - keep thick and thin filaments linked together for prolonged period, wo atp |
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involuntary control |
smooth muscle - hormones, neural stimulation by ANS - varicsitie releases neurotransmitters into synaptic cleft - visceral mucle in walls of hollow organs except heart contain pacesetter cells |
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pacesetter cells |
- these can spontaneously trigger action potential and contractions in muscle |
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on autonomic neuron is |
varicosities or boutons - axon like swelling |
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smooth muscle 2 organizations - single unit and multiunit |
single unit= visceral muscle; muscle fibers joined by gap junciton so muscle contracts as single unit (all walls of viscera organs except heart); has stress relaxation response (as muscle of hollow organ is stretched when it fills, stress of stretchin will trigger contraction, and immediatly followed by relaxation), produces slow, stead contractions that allow substances to move through the body multiunit = rarely gap junctions, not electriclly coupled, contraction is to cell that was originally stimulated; stimuli comes from autonomic nerves or hormones but not from stretching; found around large blood vessels, respiratory airways, and eyes |
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smooth muscles can divide to produce more cells |
hyperplasia - uterus at puberty increasing size of myometrium |
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most muscle tissue in body arises from |
embryonic mesoderm |
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Paraxial mesodermal cells adjacent to the neural tube form blocks of cells called |
somites. |
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skeletal muscle except those of head and limbs develop from |
mesodermal somites |
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somites give rise to |
myoblasts |
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muscle forming stem cell that migrates to diferent regions and fuses to form syncytium or myotube |
myoblast |
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- formed from different myoblast cells - many nuclei - continuous nuclei |
myotube or syncytium |
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- stem cell - incorporated into muscle cell - facilitate protein synthesis for repair and growth - outside sarcolemma - repair damage in living cells - regenerate a little |
satellite cell |
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fibrosis |
- cell damaged by greater extent where satellite cells cannot help - muscle fibers replaced by scar tissue - muscle loses strength |
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smooth muscle tissue can regenerate from stem cell called |
pericyte - in some small blood vessels - allos smooth mucle cells to regenerate and repari much more readily than skeletal and cardiac muscle tissue |
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dead cardiac muscle tissue replaced by |
scar tissue which cannot contract - as this accumulates hart loses ability to pump |
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physiotherapists |
- maintains muscles susceptible to atrophy - after breaking limb or undergoing surgery |
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4. Muscle that has a striped appearance is described as being ________. a. elastic b. nonstriated c. excitable d. striated |
d. striated |
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5. Which element is important in directly triggering contraction? a. sodium (Na+) b. calcium (Ca++) c. potassum (K+) d. chloride (Cl-) |
b. calcium (Ca++) |
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6. Which of the following properties is not common to all three muscle tissues? a. excitability b. the need for ATP c. at rest, uses shielding proteins to cover actin-binding sites d. elasticity |
c. at rest, uses shielding proteins to cover actin- binding sites |
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7. The correct order for the smallest to the largest unit of organization in muscle tissue is ________. a. fascicle, filament, muscle fiber, myofibril b. filament, myofibril, muscle fiber, fascicle c. muscle fiber, fascicle, filament, myofibril d. myofibril, muscle fiber, filament, fascicle
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b. filament, myofibril, muscle fiber, fascicle |
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8. Depolarization of the sarcolemma means ________. a. the inside of the membrane has become less negative as sodium ions accumulate b. the outside of the membrane has become less negative as sodium ions accumulate c. the inside of the membrane has become more negative as sodium ions accumulate d. the sarcolemma has completely lost any electrical charge |
a. the inside of the membrane has become less negative as sodium ions accumulate |
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9. In relaxed muscle, the myosin-binding site on actin is blocked by ________. a. titin b. troponin c. myoglobin d. tropomyosin |
d. tropomyosin |
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10. According to the sliding filament model, binding sites on actin open when ________. a. creatine phosphate levels rise b. ATP levels rise c. acetylcholine levels rise d. calcium ion levels rise |
d. calcium ion levels rise |
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11. The cell membrane of a muscle fiber is called ________. |
sacrolemma |
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12. Muscle relaxation occurs when ________. a. calcium ions are actively transported out of the sarcoplasmic reticulum b. calcium ions diffuse out of the sarcoplasmic reticulum c. calcium ions are actively transported into the sarcoplasmic reticulum d. calcium ions diffuse into the sarcoplasmic reticulum |
c. calcium ions are actively transported into the sarcoplasmic reticulum |
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13. During muscle contraction, the cross-bridge detaches when ________. a. the myosin head binds to an ADP molecule b. the myosin head binds to an ATP molecule c. calcium ions bind to troponin d. calcium ions bind to actin |
c. calcium ions bind to troponin |
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14. Thin and thick filaments are organized into functional units called ________. a. myofibrils b. myofilaments c. T-tubules d. sarcomeres |
d. sarcomeres |
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15. During which phase of a twitch in a muscle fiber is tension the greatest? a. resting phase b. repolarization phase c. contraction phase d. relaxation phase |
c. contraction phase |
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16. Muscle fatigue is caused by ________. a. buildup of ATP and lactic acid levels b. exhaustion of energy reserves and buildup of lactic acid levels c. buildup of ATP and pyruvic acid levels d. exhaustion of energy reserves and buildup of pyruvic acid levels |
b. exhaustion of energy reserves and buildup of lactic acid levels |
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17. A sprinter would experience muscle fatigue sooner than a marathon runner due to ________. a. anaerobic metabolism in the muscles of the sprinter b. anaerobic metabolism in the muscles of the marathon runner c. aerobic metabolism in the muscles of the sprinter d. glycolysis in the muscles of the marathon runner |
a. anaerobic metabolism in the muscles of the sprinter |
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18. What aspect of creatine phosphate allows it to supply energy to muscles? a. ATPase activity b. phosphate bonds c. carbon bonds d. hydrogen bonds |
b. phosphate bonds |
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19. Drug X blocks ATP regeneration from ADP and phosphate. How will muscle cells respond to this drug? a. by absorbing ATP from the bloodstream b. by using ADP as an energy source c. by using glycogen as an energy source d. none of the above |
d. none of the above |
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20. The muscles of a professional sprinter are most likely to have ________. a. 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers b. 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers c. 50 percent fast-twitch muscle fibers and 50 percent slow-twitch muscle fibers d. 40 percent fast-twitch muscle fibers and 60 percent slow-twitch muscle fibers |
a. 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers |
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21. The muscles of a professional marathon runner are most likely to have ________. a. 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers b. 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers c. 50 percent fast-twitch muscle fibers and 50 percent slow-twitch muscle fibers d. 40 percent fast-twitch muscle fibers and 60 percent slow-twitch muscle fibers |
b. 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers |
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22. Which of the following statements is true? a. Fast fibers have a small diameter. b. Fast fibers contain loosely packed myofibrils. c. Fast fibers have large glycogen reserves. d. Fast fibers have many mitochondria. |
c. Fast fibers have large glycogen reserves. |
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23. Which of the following statements is false? a. Slow fibers have a small network of capillaries. b. Slow fibers contain the pigment myoglobin. c. Slow fibers contain a large number of mitochondria. d. Slow fibers contract for extended periods. |
a. Slow fibers have a small network of capillaries. |
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24. Cardiac muscles differ from skeletal muscles in that they ________. a. are striated b. utilize aerobic metabolism c. contain myofibrils d. contain intercalated discs |
d. contain intercalated discs |
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25. If cardiac muscle cells were prevented from undergoing aerobic metabolism, they ultimately would ________. a. undergo glycolysis b. synthesize ATP c. stop contracting d. start contracting |
c. stop contracting |
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26. Smooth muscles differ from skeletal and cardiac muscles in that they ________. a. lack myofibrils b. are under voluntary control c. lack myosin d. lack actin |
a. lack myofibrils |
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27. Which of the following statements describes smooth muscle cells? a. They are resistant to fatigue. b. They have a rapid onset of contractions. c. They cannot exhibit tetanus. d. They primarily use anaerobic metabolism. |
a. They are resistant to fatigue. |
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28. From which embryonic cell type does muscle tissue develop? a. ganglion cells b. myotube cells c. myoblast cells d. satellite cells |
c. myoblast cells |
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29. Which cell type helps to repair injured muscle fibers? a. ganglion cells b. myotube cells c. myoblast cells d. satellite cells |
d. satellite cells |
