Question: what type of ion channels is necessary for the function of the axon and the axon terminal
[{'answer': 'Calcium', 'provenance': [{'wikipedia_id': '20839616', 'title': 'Axon terminal', 'start_paragraph_id': 5, 'start_character': 160, 'end_paragraph_id': 5, 'end_character': 167, 'bleu_score': 1.0, 'section': 'Section::::Nerve impulse release.\n'}]}, {'provenance': [{'wikipedia_id': '20839616', 'title': 'Axon terminal', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 1011, 'bleu_score': 0.9715305700167061, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18366680998912811612}, 'section': 'Section::::Nerve impulse release.\n'}]}]