Muscles like all tissues of the body are controlled by the nervous system. What kind of a nerve innervates a particular muscle will affect whether the muscles can be controlled voluntarily or whether it is controlled automatically. Muscles are classified according to how they are controlled by the nervous system. If a muscle can be controlled voluntarily the muscle is called a voluntary muscle most skeletal muscles are voluntary muscle. Although a few are both voluntary and involuntary.
Muscles that individuals have no control over are called involuntary muscles. Most of the body is visceral muscles are involuntary although there are a few that are both voluntary and involuntary
When food is introduced to the stomach, the stomach muscles contract and start digesting food whether you want them to or not. Stomach muscles are involuntary muscles. Likewise the cardiac muscle is an involuntary muscle the muscles that can be both are called voluntary/ involuntary muscles in respiration an example of mixed muscles automatically or hold your breath.
The appearance of skeletal muscles is striated and the nerve control is voluntary. The appearance of visceral muscle is smooth and the neeve control is involuntary and whereas the appearance of cardiac muscle is branched striated and the control can be voluntary or involuntary.