Ca Regulation In Contraction Flashcards
What is happening in the cross bridge binding sites in the absence of Ca2+?
They are hidden by tropomyosins
What are the subunits for F-actin called, those that are arranged in a double row and twisted in a helix?
G-actin
Where do the tropomyosins lie in a relaxed muscle cell?
In the groove of the actin double helix
Define troponin
Regulatory protein bound to tropomyosin
Define the relationship between troponin and Ca2+
High affinity to Ca2+
What causes the conformational change in troponin that moves tropomyosin out of the actin binding sites?
The binding of Ca2+
Where do the Ca2+ ions needed for contraction come from?
The sarcoplasmic reticulum (SR)
Describe the SR
The internal Ca2+ store
The sER of muscle cells
Around myofibril
The SR at the A-I junction fuses as the ________ ___________ that makes contact with the T tubule
Terminal cisternae
The small tubular invaginations of muscle cell membranes that intertwine among myofibrils is the ___________________
Transverse (T) tubules
Describe the function of the T- tubules
Spread of action potential from plasma membrane
With how many Terminal cisternae does the t tubule come in contact with?
2
List the things that make up a triad in the muscle fiber
2 terminal cisternae
1 t tubule
What is needed for the generation of the cross bridge cycle?
ATP & Ca2+
