The heart and lungs are signaled to either increase or decrease activity. __________________________ and...

49. The heart and lungs are signaled to either increase or decrease activity. __________________________ and __________________________
50. Glands produce hormones which then travel through the blood __________________________ and __________________________
51. Liver releases glucose and pancreas releases insulin to change sugar levels in blood. __________________________ and __________________________
52. In mammals, the blood delivers nutrients to a developing fetus. __________________________ and __________________________
53. Skin and skeleton protect the internal organs from the environment. __________________________ and __________________________
54. Specialized white blood cells travel through blood and attack pathogens __________________________ and __________________________