Muscles and movement Flashcards
How the release of Ca2+ ions in muscle fibre is stimulate
- action potential arrives at the neuromuscular junction
- neurotransmitter is released when membrane is depolarised
- Ca2+ stored in the sarcoplasmic reticulum is released into the sarcoplasm
Role of Ca2+ in muscle contraction
- binds to troponin
- moves tropomyosin
- exposing actin-myosin biding site
Role of ATP in muscle contraction
- ATP provides energy to break/form the actin-myosin bridge
- ATP used to move Ca2+ ions back into the sarcoplasmic reticulum
Which muscle fibre would enable a long distance runner to perform well
- slow twitch muscle fibre
- greater mitochondria density, more aerobic respiration can occur, krebs cycle/ETC can take place
- there are lots of capillaries to provided oxygenated blood to the muscle fibres
- myoglobin concentration is high (myoglobin stores O2 required for aerobic respiration)
Summarise the importance of glycolysis in muscle contraction
- in glycolysis two ATP is made
- NAD is reduced
- rNAD used is oxidative phosphorylation/ETC
- pyruvate is formed which is required in the link reaction/krebs cycle
Sequence of events that occurs within a muscle fibre after stimulation of neuromuscular junction
- action potential arrives at neurotransmitter arrives at neuromuscular junction
- neurotransmitter releases when membrane is depolarised
- Ca2+ stored in sarcoplasmic reticulum is released into sarcoplasm
- Ca2+ binds to troponin
- troponin causes tropomyosin to move, exposing myosin binding sites on actin
- myosin head binds to binding site on actin, forming actin myosin bridge
- myosin head moves forward (filaments slide)
- ADP + Pi released from myosin head
- actin slides over myosin
- ATP provides energy for myosin-actin bridge to break and myosin head to detach, catalysed by ATPase
Outline the differences between fast and slow twitch muscle fibres
slow twitch muscle fibres have
- more mitochondria
- more myoglobin
- less sarcoplasmic reticulum
- more capillaries
- less stored glycogen
- less creatine phosphate
- more resistant to fatigue
- respire aerobically
Would predator or prey show a higher proportion of slow twitch fibres
- prey
Discuss why predators show different proportions of fast and slow twitch muscle fibres from their prey
- predators have more fast twitch fibres than slow twitch fibres
- anaerobic respiration, glycolysis used
During fast movement, lactate builds up in muscles of quick bursts of activity, explain what happens to this lactate
- lactate removed from muscle and diffuses into blood
- the lactate formed (by pyruvate is reduced and rNAD is oxidised) is converted back into pyruvate
- lactate (pyruvate?) is oxidised to form CO2 and H2O
- energy produced to synthesise ATP
- some lactate converted to glycogen to be stored in the liver or muscle cells
Name the structures that connect muscles to bones
- tendons
Explain why muscles occur in antagonistic pairs
- muscles cannot extend themselves
- need opposing muscle to extend
- antagonistic muscle allows control of movement
Describe and explain the role of Ca2+ ions and ATP in muscle contraction
- sarcoplasmic reticulum releases Ca2+
- Ca2+ binds to troponin
- troponin moves tropomyosin exposing binding sites
- allowing myosin to bind to actin
- ATP provides energy for changing shape of myosin
- ATP required to break actin-myosin cross bridges
- ATP required to move Ca2+ ions back into sarcoplasmic reticulum
- ATP for synthesis of neurotransmitter
Name the structure that connect bones to bones
- ligaments
Describe a ligament
- holds bones together
- stills allows movement at the joint
What muscle fibre has only few mitochondria
- fast twitch (suited for intense bursts of activity)
Describe how ATP is made available for contraction of fast twitch muscle fibre, despite there being few mitochondria
- ATP from phosphorylation of ADP
- energy required for phosphorylation
- ATP produced from anaerobic respiration in cell cytoplasm (net 2ATP)
- in glycolysis, glucose is converted to pyruvate
- pyruvate is converted to lactate (pyruvate reduced)
- rNAD is oxidised, regenerating NAD for further glycolysis
- ATP from oxidative phosphorylation in mitochondria
- phosphocreatine stored in muscles can be hydrolysed to release energy
What is creatine phosphate
- immediate regeneration of ATP is achieved using creatine phosphate stored in muscles
- creatine phosphate can be hydrolysed to release energy
- this energy can be used to regenerate ATP from ADP and phosphate (phosphate from phosphate creatine)
- creatine phosphate breaks down as soon as exercise starts
- creatine phosphate + ADP –> creatine + ATP
Explain why fast twitch muscle fibre fatigue quickly
- ATP supply limited
- anaerobic respiration, lots of lactate
- pH is lower
- affects enzymes
- prevents muscle contraction
Suggest why different responses of fast and slow twitch fibres to pH may be related to their different functions in muscle
- fast twitch is anaerobic, slow twitch aerobic
- fast twitch more likely to experience low pH
- low pH due to lactate
- fast twitch is less affects by change in pH
- can respond to stimuli at a lower pH
How might pH affect muscle contraction of troponin from slow or fast twitch muscle fibres
- calcium binding site on troponin sensitive to pH
- troponin is different in each fibre
Suggest why large numbers of mitochondria are found in muscle cells
- provide ATP
- aerobic respiration
- for contraction
- for pumping Ca2+ back into sarcoplasmic reticulum
