Muscle 6 Flashcards
What initiates cross-bridging in all 3 muscle types?
An increase in calcium
What concentration of calcium is required for cross bridging?
Ca2+ > 10-7 M: Muscle contracts
What does the action potential do in regards to calcium?
Increases the internal concentration of Ca2+ near the contractile proteins
What happens in a muscle cell at low concentrations of calcium?
The myosin ADP inorganic phosphate complex cannot bind to actin
How does calcium exert it effects in the muscle?
By binding to regulatory proteins rather than directly binding to contractile proteins
What do regulatory proteins do at low concentrations of calcium?
They work together to inhibit actin myosin interactions, inhibiting the contractile process
What does Tropomyosin do at low calcium concentrations?
Blocks the actin myosin binding sites
What happens when calcium binds to one or more of the regulatory proteins?
A conformational change takes place in the regulatory complex that releases the inhibition of contraction
How many Calcium binding sites does TnC have in skeletal muscle?
- 2 high affinity and 2 low affinity
What are the high affinity sites of TnC always occupied by?
Calcium or magnesium
What occurs when four calcium are bound to TnC?
TnI and TnT undergo a conformational change which removes the steric interference moving deeper into the groove of the actin filament and out of the way uncovering the binding site of the actin filament allowing actin and myosin to bind
What two structures exist in skeletal muscle to bring calcium required for muscle contraction?
- Sarcoplasmic reticulum
* Transverse or (T-tubule) system
What does the Sarcoplasmic reticulum do in terms of skeletal muscles?
•Stores, releases and removes calcium to allow relaxation
What do the Transverse Tubules (T-tubules) do in terms of skeletal muscles?
Synchronizes the release of Ca2+
