Pharma Q

[IMG SURVIVOR]

Everybody knows that Digoxin inhibits Na-K atpasa pump but tell me why and how they give more streng to the heart?

[md90]

Everybody knows that Digoxin inhibits Na-K atpasa pump but tell me why and how they give more streng to the heart?

It increases sodium intracellularly which in turn increases the calcium coming into the cell... leading to positive inotropy; what does this mean?

the heart muscle depends on the calcium for its' contraction...entering at the plateau part of the action potential (phase 2?); calcium entering stimulates the sacroplasmic reticulum of the cardiac muscle.. releasing more calcium, and thus contraction...

please comment or add.. is all that I remember... thank you

[IMG SURVIVOR]

The plateu is fase 2 and that has Ca influx.

Phase 0 is inward of Na
Phase 1 is inside Cl and the Na close or almost close
Phase 2 Describe Above
Phase 3 K start going out side and givibg repolarization to the membrane
Phase 4 resting potential??

So where is the mistake(s) in the previous statement?

[lilianna]

That’s how I understand it:

Cardiac glycosides inhibit the Na-K ATPase causing intracellular Na raise.
Therefore NaCa antiport doesn’t function as well as before which causes intracellular Ca to increase (because less Ca is transported out of the cell).
This leads to positive inotropy:
more Ca can bind to troponin C – tropomyosin is moved out of the way – actin and myosin bind – filaments slide past each other – myocardial cells contract
→ the magnitude of the tension that develops is proportional to the intracellular Ca concentration.

Plateau 2 shows Ca influx through voltage gated Ca channels which are not opened by glycosides (but maybe triggered?)

Hope this helps…