muscle 1.3 Flashcards
what does LO mean?
greatest tension when the most cross bridges are connected
-where you want to be during a contraction
which elements effect the amounts of force that muscle fibers produce?
muscle fibers will produce different amounts of force depending on their length, because of differeing contributions from active and passive elements
how do we get the highest level of force production?
when the overlap between actin and myosin filaments is maximal, which allows the highest number of actin-myosin crossbridges to form.
what does passive tension force depend on
the force displayed by passive elements depends upon the amount that the fiber is stretched
-no actin or myosin filaments being used, proteins are being stretched like TITIN, elastic band stretching which creates energy, summation
what happens when Z lines come closer together? farther apart?
when they come closer together they overlap, usually during a concentric contraction
-more cross bridges can form
when they seperate, less cross bridges form
4 main functions of ATP
- sodium potassium pump in the plasma membrane to maintain NA+ and K+ gradients
- calcium pump in the SR provides energy for the active transport of calcium into the reticulum
- myosinATPase which energizes the cross-bridges
- binding ATP to myosin dissociates the cross-bridges bound to actin
3 ways a muscle fibre can form ATP (all phosphorylation)
- phosphorylation of ADP by creatine phosphate
- oxidative phosphorilation of ADP in the mithochondria
- phosphorylation of ADP by the glycolytic pathway in the cytosol
creatine phosphate
- rapid formation of ATP at the onset of contractile activity
- enzyme creatine kinase is needed
- formation of ATP is limited by initial concentration of CP (at rest creating CP)
-creatine phosphate donates a phosphate to ATP, energy is released when bond between creatine and phosphate is broken, this energy will form ATP
-breaking down ADP for energy
oxydative phosphorylation
- at moderate levels of muscle acitivty most ATP produced is through oxydative phosphorylation
- break down glycogen to glucose
- main one for 5-10 mins exercise
- after 30 use fatty acids less glucose
- need OXYGEN
- most common for long term moderate exercise
glycolysis
- can get glucose for glycolysis from the blood or from glycogen stores in muscle fibres
- chemical reactions
- kicks in at 70% HR
- don’t need oxygen
- 2 ATP = 4 ATP net gain 2
- LONG TERM HIGH INTENSITY exercise
end of exercise
- need to replenish creatine phosphate and glycogen
- heavy breathing to restore muscle energy systems and metabolize lactate
what occurs during muscle fatigue
- decline in muscle tension
- decreased shortening velocity
- slow rate of relaxation
onset of fatigue depends on
- muscle fiber that is active (fast or slow)
- intesity/duration of contractile activity
- degree of fitness
- peak tension cant hold as long second time muscle is activated (isometric tension)
fast twitch vs slow twitch
- fast twitch fatigue quick recover fast
- slow twitch fatigue slow recover slow
metabolic changes in active muscle during muscle fatigue (acute)
- decrease ATP
- increase ADP, Pi, Mg, O2 free radicals
- decrease calcium release, reuptake and storage by sarcoplasmic reticulum
- decrease sensitivity of thin filaments to activation by calcium
- inhibit power stroke of myosin cross bridges
