This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Myocardial  contractility  is  increased by: \nSelect and explain. \nA. Atropine, B. Decreased end diastolic volume, C. Increased  heart  rate  from  70  to  150 beats/min, D. Reduced arterial pH to 7.3', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Option A: Atropine is a muscarinic receptor antagonist that is used to inhibit the effects\xa0of\xa0excessive\xa0vagal activation\xa0on\xa0the\xa0heart, which\xa0is\xa0manifested\xa0as\xa0sinus\xa0bradycardia\xa0and AV nodal block. Effect on contractility is negligible.\xa0\nOption B: Decrease EDV decreases contractility by Frank Starling law.\nOption\xa0 D:\xa0 Acidosis,\xa0hypercapnoea\xa0and hypoxia inhibit myocardium contractility.\nOption C: This effect is known as Bowditch Effect (Myocardial tension increases with an increase in heart rate).', 'role': 'assistant'}]