system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
An investigator is studying muscle contraction in tissue obtained from the thigh muscle of an experimental animal. After injection of radiolabeled ATP, the tissue is stimulated with electrical impulses. Radioassay of these muscle cells is most likely to show greatest activity in which of the following structures?
assistant
A band