Answer:
brain belongs to nervous system
lung belong to respiratory system
heart belongs to circulatory system
liver, stomach, large intestine and small intestine all belong to digestive system
all systems work together by providing the substances needed by each of the organ systems.
If one part or organ does not function well then all other parts will be affected since the work of each organ is vital for the organism's well being, an example is if the lung is atrophied then it will take a small amount of oxygen, so less oxygen will be supplied to the different parts of the body so the individual will feel weak due to lack of oxygen.