3.6: Muscles Flashcards
What are muscle fibres made of?
Myofibrils
What are myofibrils made of?
Fused cells that share nuclei and sarcoplasm. Higher number of mitochondria
What proteins are myofibrils made of?
Actin and myosin
Describe the sliding filament theory
- Ca2+ diffuses into sarcoplasm and cause tropomyosin to move exposing the myosin head binding sites on the actin
- Whilst ADP attached to myosin heads they bind to actin forming a cross bridge
- Angle created in cross bridge creates tension and pulls acton filament to slide across myosin, relating ADP
- ATP binds to myosin head causing it to change shape and detach from actin
- ATP hydrolase hydrolyses ATP on myosin head into ADP and Pi to release energy for myosin head to return to original shape
What does phosphocreatine do?
Donate phosphate to ADP regenerating ATP short term
Describe fast twitch muscles (5)
- used for rapid and powerful contractions
- phosphocreatine used up rapidly to make ATP
- Anaerobic respiration
- ATP reforms phosphocreatine
- Higher concentration of glycogen
Describe slow twitch fibres (5)
- used for less powerful contractions
- Many mitochondria to produce ATP
- Aerobic respiration
- No stores of phosphocreatine
- Less glycogen as glucose is fully broken down
What is the A band?
Total length of myosin
What is the H zone?
Myosin area only
What is the I band?
Actin area only
What is the M line?
Middle of myosin
What forms a sarcomere?
Myosin and actin
What is the Z line?
Start and end of a sarcomere
What happens to A band, H zone, I band and Z line when muscle contracts?
- A band stays constant
- H zone decreases
- I band decreases
- Z line come closer tighter
Contrast structure of slow and fast twitch muscles
Large store of myoglobin (high affinity for oxygen to store oxygen for low pp of O2), rich blood supply and many mitochondria
vs
Thicker and more myosin, large store of glycogen, store of phosphocreatine (for ATP from ADP and Pi) and high concentration of enzymes in anaerobic respiration
Contrast location of slow and fast twitch fibres
Calf muscles vs Biceps
Contrast general properties of slow and fast twitch fibres
Contract slower and respire aerobically for longer due to rich blood supply and myoglobin oxygen store for endurance during work
vs
Contracts faster to provide short bursts of powerful contraction. Intense exercise such s sprinting or weight lifting
