The system allows locomotion, grasping, manipulating the environment, facial expression and heat generation.

Muscular system.

Explanation:

The Human muscle system i.e. the muscles of the human body work is a system consisting of skeletal, smooth and cardiac muscles that are under voluntary control. The muscular system is composed of specialized cells called muscle fibers which its function is contractibility. It permits movement of the body, maintains posture and circulates blood throughout the body.

Only a little of the equator gets to experience day and night. When Uranus revolves around the Sun one part gets light and day while the other gets light and darkness. So it changes because one time you can be looking and its day. Then you will look again and it will be night since Uranus moved around the Sun.