Muscles Flashcards
Where is the : A band, I band, H zone and Z line?
Where is the A band located? How does this change in contraction?
location of myosin [no change in contraction]
Where is the I band located? How does this change in contraction?
location between the myosin [shortens in contraction]
Where is the H zone located? How does this change in contraction?
location between the actin [shortens in contraction]
Where is the Z line located? How does this change in contraction?
end line of sarcomere [moves closer together in contraction]
Role of Ca2+ ions and ATP in muscle contraction?
- Ca2+ ions causes the tropomyosin to move exposing binding sites on actin
- Ca2+ ions stimulate ATPase
- ATP causes myosin head to detach
- ATP releases energy so myosin head returns to original position
- ATP actively transports Ca2+ ions into sarcoplasmic reticulum when the muscle is relaxed
What occurs in the first part of the sliding filament mechanism?
- the myosin heads pull the actin inwards
- the somatic motor neurone connects to the skeletal muscle via a neuro-muscular junction
- one motor neurone connects to a few muscle fibres = motor unit
- releases acetylcholine that binds to complementary receptors on the muscle fibre membrane (sarcomere)
What occurs in the second part of the sliding filament mechanism?
- Na+ channels open, Na+ ions enter the muscle fibre causing depolarisation
- wave of depolarisation travels thru sarcoplasmic reticulum
- causes release of Ca2+ ions into the sarcoplasm
- this moves the tropomyosin on the actin
What occurs in the third part of the sliding filament mechanism?
- exposes binding sites on the actin
- myosin heads now bind to the actin (cross bridge)
- a power stroke occurs, the myosin pulling the actin inwards
- ATP attaches to myosin head so it detaches
What occurs in the fourth part of the sliding filament mechanism?
- ATP brokendown by ATPase to release energy
- myosin head goes back to its original position
- so it reattaches, pulling the actin further inwards
How does fast twitch muscle fibres work?
- provide powerful but short lasting contractions
- found in biceps and sprinters
- has thicker myosin
- contains more enzymes for anaerobic respiration
- contains phosphocreatine, provides phosphate to ADP to reform ATP
How does slow twitch muscle fibres work?
- provide less powerful but long lasting contractions
- found in thigh and marathon runners
- adapted for aerobic respiration
- has a rich blood supply
- contains many mitochondria
- contains glycogen
- contains myoglobin (stores oxygen)
