Excitation-contracting coupling
7 important questions on Excitation-contracting coupling
What are the calcium concentrations outside and inside?
Intra: 100 nM (0.1 µM)
What happens during phase 2 of the AP?
Where is the developed force of the muscle dependent on?
The more calcium is present, the more binding sites are available --> more cross-bridges --> higher force
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What is the calcium-induced calcium release (CICR)?
Calcium is taken up by SR via ATP pumps to enable relaxation
How is the calcium reuptake regulated?
How is calcium removed from the intracellular space?
- Na/Ca exchange (NCX)
- SL-ATPase (SL = sarcollema)
What is the effect of sympathetic activation on the muscle cells?
- L-type Ca channels (increased Ca influx)
- Inotropic effect => stronger contraction
- Phosphorylation of phospholamban (PLB)
- lusitropic (improvement of relaxation)
- phosphorylation of troponin I (TnI)
- lusitropic (improvement of relaxation)
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