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
what happens during chronic muscle fatigue
- ryanodine receptor located in SR which are responsible for ca release during excitation contraction couple in muscles, they become leaky to calcium leading to more calcium in cytosol
- leads to activated protease that degrade contractile proteins
- leads to muscle soreness and weakness
- may have low glycogen, blood glucose, dehydration
what is central command fatigue
- mental fog
- appropriate regions of the cerebral cortex fail to send excitatory signals to the motor neurons
- could be a reason why stop exercising even when muscles are not sore
ways to classify muscle fiber types
- velocity of shortening (fast = higher maximal velocity) (slow= lower max velocity)
- major pathways they use to form ATP (oxydative or glycolitic)
3 features of a muscle contraction
- tension (determined by cross bridges)
- fatiguability (determined by supply of ATP)
- speed of contraction (determined by speed of cross-bridge cycling)
TFS THE FASTEST SPEED of muscle contraction
3 muscle fiber types
type 1 : slow oxydative fibers (SO)
type 2a : fast oxidative-glycolitic (FOG) fibers
type 2x or 2b : fast glycolitic (FG) fibers
SO FOG and FG
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Type 1 slow oxidative fibers
least powerful (slow making cross bridges)
fatigue resistant (high capacity for atp production and cellular respiration)
-use oxidative phosphorylation
slow speed of contraction (slow hydrolysis of ATP)
- rely on blood flow coming to muscle to fuel
- training increases its blood capillaries
- high capillary density, high myoglobin, high # of mithochondria
- have lot of myoglobin
myoglobin
carrier of oxygen in the muscle (small storage of 02 in muscle)
high in the lungs
fish
myoglobin
carrier of oxygen in the muscle (small storage of 02 in muscle)
high in the lungs
fish
fast glycolytic fibers 2x
very powerful (largest diameter=greatest tension)
- high myosin with high glycolitic capacity
- lower capillary density, lower myoblobin, less mithochondria
fatiguable (relies on anaerobic process for ATP)
-creatine phosphate and glycolysis
fast contraction speed
-atpase activity in myosin heads very fast (MHC 2x)
fast oxidative glycolytic (FOG) type 2a
- tension : intermediate muscle fiber diameter
- fatiguability : relies on aerobic (oxygen) and anaerobic (glycolysis) systems for ATP
- intermediate speed of contraction
how are muscle fibers usually determined
genetics
most people have what % distribution of muscle fibers
50-50 slow and fast twich
sequence of recruiting fibre types and increasing force
intially you use slow twitch until 40%
after you use glycolitic type 2a
high effort you use type 2b
wide range of muscle fibre types in same muslce
soleus vs triceps brachi
soleus has more slow twtich
triceps more fast twitch, power
