title: Do intracellular concentrations of potassium or sodium regulate the strength of the heart beat?
mesh_terms: D000818:Animals; D001001:Anura; D006321:Heart / Q000502:physiology*; D066298:In Vitro Techniques; D009119:Muscle Contraction; D009206:Myocardium / Q000032:analysis*; D011188:Potassium / Q000032:analysis*; D011894:Rana pipiens; D012964:Sodium / Q000032:analysis*; D013328:Strophanthins / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000187:drug effects
chemical_list: D013328:Strophanthins; D012964:Sodium; D011188:Potassium