muscle contraction Flashcards
(18 cards)
What is the sliding filament hypothesis?
Describes the mechanism of muscle contraction
What happens during a contraction?
Actin filaments are pulled in by myosin filaments resulting in a shorter muscle fibre
What happens to the H zone during contraction?
It gets narrower
What happens to the darker regions of the A band?
Becomes wider as there’s more overlap of myosin and actin filaments
What happens to the whole of the A band?
It stays the same
What happens to the I band?
It narrows as there is a smaller portion of non-overlapping actin filament
What happens to the Z lines?
They move closer together
What happens to the length of sarcomere?
It gets smaller
What do myosin contain that helps with contraction?
Myosin heads that extend from the myosin
What do these myosin heads have?
ATP hydrolase activity providing energy for muscle contraction
What does actin have for muscle contraction?
Binding sites for the myosin heads
What is formed between actin and myosin in muscle contraction?
Actomyosin cross bridges
What is the binding site on actin covered by?
Tropomyosin
How is muscle contraction activated?
By calcium ions released by the sarcoplasmic reticulum
What do the calcium ions do?
Bind to tropomyosin and move it out of the binding site
What does this allow to form?
Actomyosin cross bridges
What do calcium ions stimulate?
Action of ATP hydrolase which provides energy to move the myosin head pulling the actin filament and also to detach the myosin head
What happens when muscles are no longer needed?
Calcium ions are actively transported back into the sarcoplasmic reticulum
