AI overview (actually Iasper)
Histology and cellular anatomy of skeletal muscle cells
intercalated disk has gap junctions and desmosomes this allows attachment and passage of electrical pulses
actin myosin
calcium binds to troponin and tropomyosin uncouples from actin active site
excitation contraction coupling
excitation contraction
electrical impulses lead to extracellular ca2+ intake (25% of needed ca) and release of ca 2+ from sacrolemma (75% of needed Ca)
calcium is released form the sarcolemma by ca 2+ ryr uses calcium as a trigger to release calcium
high density around L-type ca channels in the plasma membrane
relaxation restitution
we also pump calcium out of the cell with a series of pumps and exchangers as well as back into the sr
1 SERCA pumps calcium into SR PLN tends to inhibit SERCA-2 while it is dephosphorylated
2 Sodium calcium exchange pump
3 calcium ATPase
Changing the pump
- make heart a better pump (improve pumping action)
- SNS/ contractility/ positive inotropic effect
- improve operating conditions
- starlings law, filling / output
Positive inotropic changes
aderingeric sympathetics sympathetic contraction
- binding of NA to b1 adrenoceptors in cardiac muscle cell
- increased concentration of cAMP
- activation of protein kinase A
- PKA phosphorylates Ltype calcium channels and RyR channel (and phospholamban?)
- more ca2+ ion enter per impulse