Question: electrical impulses are conducted efficiently through cardia muscle via
[{'answer': 'the Purkinje fibers', 'provenance': [{'wikipedia_id': '26862016', 'title': 'Cardiac physiology', 'start_paragraph_id': 15, 'start_character': 325, 'end_paragraph_id': 15, 'end_character': 344, 'bleu_score': 1.0, 'section': 'Section::::Electrical conduction.\n'}]}, {'provenance': [{'wikipedia_id': '26862016', 'title': 'Cardiac physiology', 'start_paragraph_id': 15, 'start_character': 0, 'end_paragraph_id': 15, 'end_character': 402, 'bleu_score': 0.9716239638199891, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11624149325446982119}, 'section': 'Section::::Electrical conduction.\n'}]}]