paper 2: Muscles Flashcards
how do muscle act
in antagonsitic pairs
what do muscle do
move bones at a joint and are attached to bones by tendons
how do msucles produce a movement
muscle contract against incompressable skeleton
what does antagonistic mean
when one muscle contracts the other of the pair relaxes
draw a labelled diagram showing the gross structure of skeletal muscle, illustrating the arrangements of muscle fibres into many bundles surrounded by connectuve tissue
draw and label a diagram to show the microscoping structure of skeletal muscle fibre including sarcolemma, sarcoplasmic reticulum, thick myosin, this myofillaments (actin), mitochondria and sarcomeres
draw the ultrastructure of a myofibril, showing the arrangements of actin and myosin myofilaments in repeating sarcomere units
draw a diagram showing a simple drawing of a repeating sarcomere unit
what happens ot the H zone of a muscle fibre when the muscle contracts
gets shorter
what heppens to the I band in a muscle fibre when the msucle contracts
gets shorter
what happens to the A band of a muscle fibre when a muscle contracts
stays the same
what theory describes when a muscle contracts
sliding filament theory
what are thin filaments made out of
actin plus tropomyosin
whar are thick filaments made from
myosin which have 2 heads and a tail
what happens to the thick fillaments in muscle fibres when they contract
- myosin head attach to binding sites on the actin, forming actinmyosin bridges
- when relaxed the binding site on the actin is covered by tropomyosin
describe the stages of myofibril contraction
- action potentials depolarise the sarcolemma and T-tubules
- voltage gated Ca2+ ion channels on the sarcoplasmic reticulum membrane open
- calcium ions diffuse from sarcoplasmic reticulum into the myofibril
- calcium ions cause the tropomyosin to move, exposing myosin bunding istes of the actin
- myosin heads bind actin forming actinmyosin bridges
- calcium ions also acitvate ATP hydrolase
- energy from hydrolysis of ATP cause myosin heads to bend and pull the actin
- attachment of ATP to the mysoin heads causes them to detach from actin
- myosin heads move back to thier original position ans reattach at binding sites further along the actin
what is the role of phosphocreatine in providing energy during muscle contraction
it donates a phosphate to reform ATP quickly, from ADP + Pi, in anaerobic conditions
what happens to phosphocreatine when muscle is relaxed
- creatine is phosphorylated back to phosphocreatine using Pi from ATP made in respiration
what are slow twitch fibres adapted for
aerobic respiration (endurance)
what are fast twitch fibres adapted for
anaerobic respiration (quick powerful contractions)
what are the characteristics of slow twitch muscle fibres
- slow speed of contraction
- low force of contraction
- adapted for aerobic respiration to prevent lactic acid build up
- large myoglobin stores
- has many mitochondria
- adapted for endurance work such as standing and marathon running
- has a large number of capillaries (provide a shorter diffusion distance/ large surface area)
what are the charcteristics of fast twitch muscle fibres
- have a high concentration of enzymes for anaerobic respiration
- contract rapidly with short powerful contractions
- have a store of phosphocreatine, to provide phosphate to genarate ATP
- have a large store of glycogen
- have thicker more numerous myosin fibres
