Kaplan Nursing Entrance Practice Exam

What system allows organisms to respond to stimuli from their environment?

1. Circulatory system

2. Nervous system

3. Endocrine system

4. Immune system

The correct answer is: Nervous system

The nervous system is the primary system responsible for allowing organisms to respond to stimuli from their environment. It operates through complex networks of neurons that communicate signals rapidly across the body. When a stimulus is detected—such as a sound, light, or touch—sensory receptors send information to the brain, which processes it and determines an appropriate response. This response can include immediate actions, like reflexes, or more complex behaviors requiring conscious thought. While the circulatory system, endocrine system, and immune system have essential functions in the body, they do not play the primary role in responding to environmental stimuli. The circulatory system is involved in the transport of blood and nutrients but does not directly interpret stimuli. The endocrine system regulates body functions through hormones, which often involve a slower response, while the immune system is focused on defending the body against pathogens rather than responding to environmental changes. Thus, the nervous system is uniquely designed for quick and effective responses to stimuli.