B3.3 Muscle & Motility Flashcards
What is a sessile organism?
organism that remain in one location
What is locomotion?
moving from one place to another
What are myofibrils?
thread-like structures in muscles composed of repeating sacromeres
What are sacromeres?
contractile unit of a muscle
What are sacromeres composed of?
thick filaments (myosin) and thin filaments (actin)
What is a Z-line, where is it and what is it’s function?
boundary of a sacromere, has actin filaments attached
What is a M-line, where is it and what is it’s function?
in the centre of a sacromere, middle of myosin filaments
What happens to Z-lines during contraction?
they are coming closer together
What is an I band?
region where only actin is present
What is an H band?
region where only myosin is present
What is an A band?
region where myosin is present when muscle is relaxed and overlap between actin and myosin when muscle is contracted
What is the sliding filament theory?
when muscle contracts, actin filaments slide over myosin filaments towards the centre of the sacromere
Explain the pathway/steps of muscle contraction on sacromere level (4)?
- myosin head with ATP attached hydrolyses ATP into ADP
- myosin head attaches to actin (crossbridge formed)
- myosin head bends and moves actin towards centre
- another ATP attaches to myosin head causing it to detach from actin
What is tropomyosin?
protein that covers the surface of actin to prevent the myosin heads from attaching unnecessarily when muscle is relaxed
What is troponin?
protein that moves tropomyosin away when calcium attaches
What is sacroplasm?
cytoplasm of muscle cell
Where are calcium ions released from?
sacroplasmic reticulum
What causes a muscle to go from relaxed to contracted state?
release of calcium that binds to troponin and move away the tropomyosin, so myosin heads can bind
What’s the role of titin in muscle contraction (3)?
- connecting Z discs and M lines to provide support and stability
- helps sacromeres to come back to normal state
- prevents overstretching
