Final answer:
Mitral valve prolapse is characterized by a backward movement of one of the valve cusps, disrupting the normal flow of blood and causing regurgitation. This condition can be detected through the presence of a heart murmur.
Step-by-step explanation:
When the mitral valve prolapses, it means that one of the cusps of the valve is forced backward by the force of the blood. This causes the valve to fail in closing properly, disrupting the normal flow of blood and resulting in regurgitation. Using a stethoscope, the disruption to the normal flow of blood produces a heart murmur, which is an unusual sound caused by turbulent blood flow.