Question: what allows the nerve impulses that initiate muscle contraction to travel along the sarcolemma
[{'answer': 'Transverse tubules', 'provenance': [{'wikipedia_id': '2302081', 'title': 'T-tubule', 'start_paragraph_id': 1, 'start_character': 11, 'end_paragraph_id': 1, 'end_character': 29, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]