Which two body systems are responsible for controlling all muscle contractions in the body?

• A. Nervous and Endocrine
• B. Nervous and Muscular
• C. Circulatory and Excretory
• D. Digestive and Immune

Answer: (B)

The correct answer highlights the essential roles of the nervous system and the muscular system in controlling muscle contractions. The nervous system plays a critical role in initiating and regulating muscle contractions by sending signals to muscle fibers through motor neurons. This communication allows for precise control of voluntary movements, such as walking or grasping objects, as well as involuntary movements, such as the beating of the heart or peristalsis in the digestive tract.

The muscular system comprises the various types of muscle tissue, including skeletal, cardiac, and smooth muscles, each responsible for specific functions and types of movement. Skeletal muscles, for instance, are directly controlled by the nervous system, enabling conscious movement, while cardiac and smooth muscles respond to signals from both the nervous system and hormones produced by the endocrine system.

In contrast, the other answer choices reference systems that do not directly control muscle contractions. The circulatory and excretory systems are primarily involved in the transport of nutrients, oxygen, and waste removal, whereas the digestive and immune systems focus on digestion and defense, respectively. Therefore, the nervous and muscular systems are indeed the two systems that work together to facilitate and control all muscle contractions in the body.