Muscles 6.3 Flashcards
How so muscles produce movement?
Contract against an incompresible skeleton moving the bone at a joint
What are muscles attached to bones by?
Tendons
What does antagonistic mean?
Muscles act in antagonistic pairs when one contracts the other relaxes
What happens when a muscle contracts?
H zone gets shorter I band gets shorter A band stays the same
What is the sliding filament theory?
Actin filaments slide over myosin filmanets
Myosin heads attach to actinomyosin bridges when relaxed the binding sight is covered by tropomyosin
What are thin filaments made of?
Thin filaments are made of actin and tropomysosin
What are thick filaments made of?
Thick filaments consist of many myosin molecules each molecule has a tail and a head
What are the stages of microfibril contraction?(sliding filament theory)
Action potential depolarises Sarcolemma and T-tubules
Voltage gated calcium ion channels on the sarcoplasmic reticulum membrane open
calcium ions diffuse from the sarcoplasmic reticulum into the microfibril
calcium ions bind to troponin receptors causing tropomyosin to move expsosing myosin binding sites on the actin
Myosin heads bind actin forming actinmyosin bridges
Calcium ions activate ATP hydrolase
Energy from the hydrolysis of ATP causes to bend and pull the actin
myosin heads to detach from actin from attachment on atp to myosin head
Myosin heads move back to their original posistion and reatach at binding sights further along actin
What is phosphocreatine used for?
Stored in muscles
Donates a phosphate to ADP to reform ATP quickly in anaerobic conditions
When muscle is relaxed creatin is phosphorylated back into phosphocreatin using Pi from ATP made in respiration
Why is phosphocreatine needed
ATP cannot be stored in muscles
Can form ATP quickly only requires a hydrolysis of phosphocreatine and condesation of ADP + Pi (2 reactions)
What are fast fibres adapted for?
anaerobic respiration quick powerful contractions (eg for sprinting)
What are slow fibres adapted for?
aerobic respiration endurance (eg long distance runner)
How are fast fibres adapted? (5)
High concentration of enzymes for anaerobic respiration
Contract rapidly with short powerful contractions eg biceps
Have a store of phosphocreatin, to provide phosphate to generate ATP
Have a large store of glycogen
Have thicker more numerous myosin fibres
How are slow fibres adapted? (6)
Contract more slowly with less powerful contractions
Adapted for aerobic respiration to prevent lactic acid build up
Have a large store of myoglobin(molecule which stores oxygen
Many mitochrondria
Adapted for endurance work such as standing and marathon running eg back muscles
Very closely associated with a large number of cappilaries (larger surface area shorter diffusion pathway
