7: Skeletal Muscle Contraction Flashcards
DHP receptor
voltage sensor on t-tubules
RYR receptor
Ca+2 channel on SR
SERCA pump
Ca+2 pump on SR (requires ATP and generates heat)
Terminal cisternae
the portions of the SR closest to the t-tubules with increased Ca+2 storage ability due to calsequestrin
Calsequestrin
a Ca+2 binding protein that holds Ca+2 in the TC after muscle contraction
Excitation-contraction coupling
the transmission of electrical excitation to the actomyosin system
Tropomysosin
interwining rod-like proteins that regulate access of mysoin heads to actin
Troponin C
complex globular protein that has an affinity for Ca+2 and also binds to tropomysonin and actin
Titin
large elastic protein that helps to maintain the side-by-side relationship of actin and mysoin
Excitation-contraction coupling steps
- ACh binding to receptors causes influx of Na+
- EPPs lead to AP that pass along the sarcolemma and t-tubules
- Depolarization of t-tubules opens Ca+2 channels on SR (RYRs)
- Ca+2 released from SR and flows into sarcoplasm
- Ca+2 binds to troponin-C
- Troponin-C allows access for mysoin head binding on actin
- Myosin head ratches to pull actin towards center of sarcomere, leading to contraction of sarcomere
What is the effect of limiting ATP?
rigor mortis
Isometric contraction
increased tension, no shortening
Isotonic contraction
tension greater than opposing load, shortening occurs
ATP binding to mysoin head causes what?
mysosin released from actin
What happens when ATP begins hydrolysis to ADP and Pi?
myosin head extends
