True about cardiac muscle fibers ?
a) Digitalis decreases force of contraction
b) Na+ - Ca+ exchanger requires ATP directly
c) Na±Ca+ exchanger acts to pump Ca2+ into heart muscle cells
d) All are true
Correct Answer - C
Ans. C. Na±Ca+ exchanger acts to pump Ca2+ into heart
This pump transports Ca+2 in exchange of Na+.
When Na+ concentration inside the myocyte is high, Na+/Ca+2
exchanger cause efflux of Na+ out of the myocytes and in exchange
it causes influx of Ca+2 inside the myocytes.
Na+/Ca+2 exchanger does not require ATP to function, ions move
along their concentration gradient.