Practice question

When a nerve impulse finally reaches a muscle at the neuromuscular junction, the muscle fibres must move to complete the response. This critical movement occurs at the microscopic cellular level when individual muscle cells change their shape to shorten. Muscle cells specifically achieve this dramatic shape change using specialized cellular proteins. When the electrical nerve impulse properly stimulates the muscle, it triggers a complex cascade that rapidly alters both the physical shape and the internal structural arrangement of these special proteins within the cell. This newly formed arrangement invariably results in a much shorter, contracted form of the muscle cells. Consequently, this causes the entire muscle tissue to pull and contract, thereby producing the desired physical movement or action in direct response to the original environmental stimulus. Thus, the fundamental cellular response of these tissues to a nerve impulse is to immediately change their physical shape.