Question: where is acetylcholine released from to stimulate muscle contraction
[{'answer': 'the neuromuscular junction', 'provenance': [{'wikipedia_id': '52649', 'title': 'Acetylcholine', 'start_paragraph_id': 2, 'start_character': 46, 'end_paragraph_id': 2, 'end_character': 72, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '52649', 'title': 'Acetylcholine', 'start_paragraph_id': 19, 'start_character': 0, 'end_paragraph_id': 19, 'end_character': 538, 'bleu_score': 0.9451526628827591, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5416318614088283672}, 'section': 'Section::::Functions.:Neuromuscular junction.\n'}]}]