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cardiac muscle contraction

6K views 3 replies 4 participants last post by  Shooting Star 
#1 ·
Micro electrodes placed in cardiac muscle cells detect a rapid decrease in cytoplasmic calcium level immediately preceding relaxation. Which of the following mediates the observed response?

A- Voltage dependent calcium channels
B- Ryanodine receptors
C- Na/Ca exchanger pump
D- Troponin C
E- Calmodulin
 
#4 ·
Ryanodine receptors (RyRs)are not restricted to striated muscle.
RyR1 is expressed predominantly in fast- and slow-twitch skeletal muscle
RyR2 was originally purified from cardiac muscle (it is the major isoform expressed there), but is also robustly expressed in neurons, and in visceral and arterial smooth muscle too.
 
#3 ·
yes the answer is C.

the easiest way to remember is the figure in kaplan pharmacology that describes the action of digoxin to block Na/K+ ATPase n then the increased in Na intracellular causes a block in Na/Ca exchange, thus increasing intracellular Ca2+ as well.:happy:
 
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