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10 Cards in this Set
- Front
- Back
Explain why a position on a sarcomere may appear darker at diff period of time? |
Movement of actin betwen myosin Contraction of muscle |
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Describe the role of calcium ions in the contraction of a myofibril |
Calcium ions bind to troponin/Move tropomyosin Expose myosin binding sites on actin filament Allow cross-bridges to form/myosin to bind to actin activates ATPase for hydrolysis of ATP |
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Explain what causes the cross bridges between actin and myosin to remain firmly bound after death |
No respiration No ATP produced ATP used for separation of actin and myosin/cross-bridged |
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Describe what causes the different bands seen in the muscle myofibril |
A-band; mainly myosin filaments I-band; actin filaments darker band; both filaments H-zone; just myosin |
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Describe how the banding pattern of a sarcomere is different during contraction |
H-zone and I-band narrower A-band same size/dark band wider |
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Explain the importance of ATPase during muscle contraction. |
Hydrolysis of ATP into ADP and P releasing energy Energy used to break actin-myosin bridges |
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Describe the role of ATP and phosphocreatine in producing contraction of a muscle fibre |
ATP allows myosin to detach from actin 're-cocks' myosin cross-bridge phosphocreatine allows regeneration of ATP in anaerobic conditions Releases Pi to join with ADP |
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Endurance athletes have a high proportion of slow twitch fibres. Explain the benefit |
Endurance athletes excercise for extended period of time Respire aerobically Lactate does not accumulate Many mitochondria Site of Krebs cycle And ETC Produce a lot of ATP High resistance to fatigue Myoglobin + rich supply of blood vessels |
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Nerve impulses arriving at the presynaptic membrane at the neuromuscular junction result in shortening of sarcomeres. Describe how. |
Opening of Ca channels, enters synaptic knob Vesicles with acetylcholine fuse with membrane Acetylcholine diffuses across cleft Binds to specific receptors on sarcolemma Causes depolarisation (changes permeability to Na+) Action potential travels through T-tubules to cause Ca ions to diffuse out of sarcoplasmic reticulum Ca binds to troponin and moves tropomyosin exposes binding sites allows cross-bridges to form change in angle causes sliding filament |
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Explain why no force is generated when the sarcomere length is at its max? |
No overlap No cross-bridges form No contraction |