The skeletal muscles are under voluntary (conscious) control most of the time. However, skeletal muscle movement can also by induced by involuntary reflexes.
Reflexes are involuntary reactions to a stimulus such as the burning of the hand. As soon as a hot substance contacts the hand, pain receptors in the skin send a signal to the spinal cord. In turn, the spinal cord sends a signal back to the arm muscles that instruct the hand to pull away. The arm flexed as it withdrew, which is known as a flexor (withdrawal) reflex.
If the body did not have the reflexes to withdraw quickly from a painful stimulus, we would be at risk for serious injury.Unsupported extension