Muscle contraction Flashcards
What molecule is liberated into the synaptic cleft by synaptic vesicles?
Acetylcholine
What occurs when Ach binds to receptors on the post-synaptic membrane?
- Na+ ions enter the cell2. K+ ions leave the cell3. Sarcolemma depolorizes
What protein is contained within the sarcoplasmic reticulum?
Calsequestrin
Where is calsequestrin located?
Sarcoplasmic reticulum
What is the role of calsequestrin?
Stores calcium ions and liberates them into the cytoplasm, in the region overlapping thick and thin filaments (goes from SR and into cytoplasm)
What subunit of troponin do calcium ions bind to?
TnC
What happens when TnC binds calcium ions?
- TnT pushes tropomyosin filaments to move deeper into the spiral groove of actin, exposing actin active sites2. Myosin head associates with actin monomer (ATP expended)3. Head and neck of myosin bend4. Myosin pulls the actin filament over the myosin filament, resulting in sliding of thin filament toward midline of sarcomere
What happens to the length of thin filaments during contraction?
Remains the same!
What happens to the length of thick filaments during conraction?
Remains the same!
During contraction, what happens to the A band?
Remains the same size
During contraction, what happens to the H band?
Almost disappears
During contraction, what happens to the I band?
Becomes smaller
During contraction, what happens to the Z discs?
Approaches midline
What happens during rigor mortis?
Actin-myosin complexes cannot dissociate since ATP is not available - muscles stiffen