By Angie Papple Johnston

Your body consists of several major systems that work together to keep you alive, so you may see questions on this topic on the ASVAB. The following table lists the components and functions of all our body systems.


Your nervous system is at the wheel, controlling everything that happens in your body. Your cardiovascular system pumps blood to spread oxygen to all your organs and tissues—but it couldn’t do that if your respiratory system wasn’t bringing in the oxygen in the first place. Your musculoskeletal system enables you to keep bringing in food by eating, and your digestive system turns the food into fuel for your nervous system (and all your other systems).

Some of these functions are involuntary, like breathing and pumping blood through your body. Others, such as eating, running, and scratching the itch on your foot, are voluntary—they require you to actively choose to do something (even if it happens within a split second) and then act on your impulse. When your nervous system takes in stimuli (either through one of your external senses or through an internal stimulus, like hunger), it kicks into high gear. It sends chemical and electrical signals out to the organs that need to participate in what’s happening next, and they take action.

Practice question

  1. The intestines are part of the

A. circulatory system.

B. nervous system.

C. respiratory system.

D. digestive system.

Answer and explanation

  1. The correct answer choice is D.

Both the large and small intestines are part of the digestive system.