Write the two main systems involved in the blanks. 49. The heart and lungs are signaled to either increase...

Write the two main systems involved in the blanks.
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 __________________________