Question: which part of the heart normally controls the heart rate
[{'answer': 'the sinoatrial node', 'provenance': [{'wikipedia_id': '304942', 'title': 'Heart rate', 'start_paragraph_id': 4, 'start_character': 44, 'end_paragraph_id': 4, 'end_character': 63, 'bleu_score': 1.0, 'section': 'Section::::Physiology.\n'}]}, {'provenance': [{'wikipedia_id': '304942', 'title': 'Heart rate', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 553, 'bleu_score': 0.9754554449993441, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16752223803933522374}, 'section': 'Section::::Physiology.\n'}]}]