Term
| What are the 3 types of muscle tissue? |
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Definition
Skeletal -> pull on bone to move body
Cardiac -> pumped blood round the cardiovascular system
Smooth -> pushes solids and fluids (eg. along the digestive tract and regulates small artey diameter) |
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Term
| What is the hierarchial structure of skeletal muscle (from biggest to smallest)? |
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Definition
Connective tissue
Muscle fibres
Myofibrils
Sacromeres |
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Term
| What occurs at the ends of muscles? |
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Definition
| collagenous networks interlink to form tendons. |
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Term
| What do the perimysium, epimysium and endomysium cover? |
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Definition
Ep: surrounds the muscle
P: covers the fasicles
End: surrounds individual fibres |
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Term
| What are the 3 techniques used to view sacromeres? |
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Definition
| Dark field, compound, confocal |
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Term
| When would dark field imaging be used? |
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Definition
| enhances contrast in low contrast specimens |
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Term
| When would compound imaging be used? |
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Definition
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Term
| When would confocal imaging be used? |
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Definition
| Increases optical resolution by removing out of focus fluorescent light. Can build 3D images if scan multiple sections. |
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Term
| What are myofibrils made up of? |
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Definition
| actin and myosin proteins that assemble into serially arranged thick and think filaments called sacromeres. |
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Term
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Definition
protein bound to actin which holds the F-actin strand together.
extends along the thin filaments and the entire I-Band. |
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Term
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Definition
elastic myofilament which connects the thick filament to the z-line.
the portion exposed in the I-band is elastic which means it recoil after stretching. |
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Term
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Definition
| a protein which binds and caps the minus end of actin (the "pointed" end), regulating the length of actin filaments |
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Term
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Definition
| A sarcomere is defined as the segment between two neighbouring Z-lines |
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Term
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Definition
| I-band is the zone of thin filaments that is not superimposed by thick filaments. |
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Term
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Definition
| An A-band contains the entire length of a single thick filament. |
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Term
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Definition
| H-band is the zone of the thick filaments that is not superimposed by the thin filaments. |
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Term
| Describe basic muscle contraction |
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Definition
Ca2+ binds to receptors on troponin
Troponin-tropomyosin complex changes position
Active site on actin is exposed |
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Term
| What is the stimulus for a skeletal muscle fibre contraction? |
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Definition
| When stimulated by a motor neurone at a neuromuscular junction. The stimulus arrives in the form of an AP at the axon terminal. |
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Term
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Definition
| the release of ACh into the synaptic cleft, which leads to excitation - the production of an AP in the sarcolemma. |
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Term
| What does the AP in the sarcrolemma cause? |
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Definition
| the AP travels along the sarcolemma and down the T tubules to the triads. This triggers the release of Ca2+ from the terminal cisternae of the sarcoplasmic reticulum. |
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Term
| What begins when Ca2+ are released from the sarcoplasmic reticulum? |
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Definition
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Term
| Describe the contraction cycle |
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Definition
| Ca2+ bind to troponin resulting in the exposure of the active sites on the think filaments. This allows cross bridge formation and will continue as long as ATP is available. |
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Term
| What occurs after the power-stroke? |
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Definition
| the ADP and phosphate group that were bound to the myosin head are released |
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Term
| How does the myosin head and actin separate? |
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Definition
| When another ATP molecule binds to the myosin head, the link is broken. The myosin head is re-cocked using the energy released from splitting ATP into ADP and P. |
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Term
| What does muscle type depend on? |
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Definition
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Term
| Describe the fascicle arrangement for fusiform muscle |
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Definition
| wide and CYLINDRICAL in centre yet TAPERED at end |
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Term
| Describe the fascicle arrangement for parallel muscle and what is it good for? |
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Definition
fascicles are PARALLEL to the long axis of the muscle.
fast extensive movements |
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Term
| Describe the fascicle arrangement for convergent muscle |
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Definition
| muscle fascicles converge onto one attachment site |
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Term
| Describe the fascicle arrangement for pennate muscle and the different types |
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Definition
fascicles follow the same angle as each other.
uni/bi/multi |
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Term
Which can generate more force, parallel or pennate?
which can shorter quicker? |
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Definition
pennate because it has a larger cross-section area and more myofibrils.
parallel |
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Term
| why do convergent muscles produce less force than parallel muscles? |
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Definition
| fibres pull in various directions however this makes it versatile. |
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Term
| What do circular muscles act as? |
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Definition
| entrances, exits and valves. they contract to narrow openings. |
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Term
| do muscles change volume during contraction? |
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Definition
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Term
| How do I bands change during contraction? |
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Definition
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Term
| How do Z lines change during contraction? |
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Definition
they move closer together
(the ends) |
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Term
| How do A bands change during contraction? |
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Definition
they do not change width
myosin and actin overlap |
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Term
| Describe the cross-bridge cycle |
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Definition
1. myosin bound to actin
2. ATP binds to myosin, causing it to dissociate from actin
3. myosin ATPase hydrolyses ATP into ADP and Pi
4. myosin head moved to cocked position and binds to G-actin
5. Pi released and stable, force producing cross bridge is formed
6. ADP unbinds from mosin and remains tighly bound to actin |
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Term
| Describe the mechanism that leads to rigor mortis |
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Definition
1. following death ATP is gradually used up
2. ca2+ in sarcoplasmic reticulum rises
3. normal E-C coupling occurs, cross bridges form
4. filaments slide but there is no ATP to detach the cross bridges so they remain locked in the contracted position. |
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Term
| what is an isotonic contraction? give examples |
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Definition
muscle length changes and the tension increases.
lifting an object off the desk, walking, running
load would be kept constant in an experiment. force and work and power generated |
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Term
| what is an isometric contraction? give examples |
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Definition
muscle length remains the same and the tension produced does not exceed the load.
holding a baby at arms length
load would be varied during experiment.
force generated. |
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Term
| what is the equation for work? |
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Definition
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Term
| what is the equation for power? |
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Definition
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Term
| what is an isometric twitch? |
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Definition
| produced in response to a single stimulus |
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Term
| what is the latency period? |
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Definition
| delay between stimulus and rise in force. Includes stimulation, AP -> sarcolemma, SR -> Ca2+ |
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Term
| what events occur in contraction? |
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Definition
| Ca2+ binds to troponin, active site exposed and cross bridge forms. force rises to peak. |
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Term
| what events occur in relaxation? |
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Definition
| ca2+ decreases. active sites covered. cross bridges detach. force decreases to resting level. |
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Term
| what does force/tension generated depend on? |
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Definition
| the amount of overlap between thick and thin filaments. At long sacromere lengths, filaments do not overlap therefore no force generated. |
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Term
| what is the resting membrane potential? |
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Definition
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Term
| what is the threshold potential potential? |
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Definition
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Term
| Describe the events of an skeletal muscle fibre action potential |
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Definition
1.threshold potential reached as K+ leaked out. Na+ and Ca2+ (through voltage dependent Ca2+ channels) slowly flow in.
2. Membrane is depolarised as K+ rapidly leaks
3. membrane repolarised as ca2+ channels close. Na+ permeability decreases and K+ permeability increases |
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Term
| Describe the events of an cardiomyocyte action potential |
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Definition
1. Rapid depolarisation: Na+ influx as voltage dependent channels open.
2. Plateau: Na+ channels close and Ca2+ channels open. Efflux of Na+ and Influx of Ca2+
3. repolarisation: Ca2+ channels close and K+ open. Efflux of K+ from cell restoring resting potential |
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Term
| Which has the longer refractory period and longer AP |
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Definition
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Term
| What are intercalated discs and what do they allow? |
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Definition
cardiac muscles consist of individual cardiac cells that are joined by intercalated discs to work as one whole organ.
they allow chemical, electrical and mechanical communication between cells.
Sacrolemmas of adjacent cells connected at gap junctions and desmosomes. |
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Term
| Where are smooth muscle cells found? |
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Definition
| in the gut, airways and blood vessels. They can be multi-layered. |
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Term
| how are actin and myosin organised in skeletal and cardiac muscle cells? |
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Definition
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Term
| Describe the structure of a smooth muscle cell |
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Definition
| Relatively long and slender with a single central nucleus. |
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Term
| Describe a smooth muscle fibre |
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Definition
No T Tubules
sarcoplasmic reticulum forms a loose network through the sarcoplasm |
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Term
| Why is smooth muscle called nonstriated? |
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Definition
| lack myofirbrils and sarcomeres and therefore has no striations |
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Term
| Describe the arrangement of thin and thick filaments |
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Definition
thin = attached to dense bodies
thick = scattered throughout the sarcoplasm of SMC. |
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Term
| How are smooth muscle cells connected? |
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Definition
| by gap junctions which facillitates the spread of chemicals and AP. The spread of depolarisation makes cells contract in a wave. |
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Term
| Describe ECC in smooth muscle cells |
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Definition
1. external ca2+ enters through voltage channels
2.small amounts are released from internal stores
3.ca2+ bind to calmodulin
4.complex activates MLCK
5.MLCK phosphorylates 20kDa light chain on myosin
6.This activates myosin (contraction) |
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Term
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Definition
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Term
| What is the equation for force? |
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Definition
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Term
| What is the equation of moment? |
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Definition
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Term
| What is potential energy? |
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Definition
| energy of an object due to its height |
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Term
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Definition
| energy of an object due to its speed |
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Term
| What are the functions of tendons? |
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Definition
- allow transmission and redistribution of muscoskeletal forces across joints
- facilitate wider joint movement
- reduce weight
- save energy
- act as springs |
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Term
| what causes a contraction? |
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Definition
| sudden change in membrane potential |
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Term
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Definition
| surrounds the sarcoplasm and has a membrane potential due to -ve charges on inside and +ve on outside |
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Term
| What are transverse tubules? |
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Definition
where the signal is conducted by
filled with ecf and form passageways through muscle fibre |
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Term
| what is the sacroplasmic reticulum |
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Definition
| a membrane complex that forms a tubular network around each myofibril |
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Term
| What does the tensio produced by an individual muscle fibre depend on? |
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Definition
the fibres resting length at time of stimulation (determine overlap)
frequency of stimulation (affects internal conc of ca2+) |
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Term
| What is treppe and where do you find it? |
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Definition
if a skeletal muscle is stimulated a second time immediately after relation phase, the next contraction will have higher tension.
phenomenom in cardiac muscle |
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Term
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Definition
| occurs when successive stimuli arrive before the relaxation phase has been completed. contraction strength increases |
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Term
| what is incomplete tetanus |
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Definition
| stimuli increases further and tension reaches a peak and relaxation phases are brief |
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Term
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Definition
| occurs when stimulus frequency is so high that relaxation phase is eliminated |
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Term
| what is isotonic concentric contraction? |
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Definition
| muscle tension exceeds the load and muscle shortens |
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Term
| what is isotonic eccentric contraction? |
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Definition
| peak tension is less than the load and the muscle elongates due to the contraction of another muscle |
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