1 Voltage can be thought of as the driving force (although it is not really a force.) behind current. 2  Things like batteries are voltage sources. 3  The voltage across the terminals of a battery tends to stay pretty constant. 4  When you connect a device across the battery terminals a current flows through the device.
Three types of muscles. The muscular system can be broken down into three types of muscles: skeletal, smooth and cardiac, according to the NIH. Skeletal muscles are the only voluntary muscle tissue in the human body and control every action that a person consciously performs. Most skeletal muscles are attached to two bones across a joint, so the muscle serves to move parts of those bones closer to each other, according to The Merck Manual.
Muscular System. The muscular system is composed of more than 600 muscles. These include the involuntary muscles of the heart and the smooth muscles of the internal organs. The skeletal muscles connect to the bones and work with connective tissue at the joints to allow for movement. The muscles connect to the nervous system and allow initiation of movement through nerve signals to and from the brain.