Red and white muscle are subtypes of skeletal muscle, referring to the color of the muscle due to blood supply and also cellular amounts of myoglobin protein. Myoglobin binds oxygen very tightly, releasing the oxygen only when cell levels of oxygen become very low. In this way myoglobin can be though of as a type of cellular scuba tank. Fast twitch muscle fibers are adapted for sprinting and strength, and also correspond to white muscle. Slow twitch muscle fibers are adapted for endurance, and correspond to red muscle.
Smooth muscle is involuntary, being under the control of the autonomic nervous system.
This muscle type is found in the walls of hollow, internal, organs- such as blood vessels, gallbladder, intestine, stomach, and lung airways. Cardiac muscle is located in the wall of the heart, and like smooth muscle is under involuntary control. Cardiac muscle tissue has special cellular properties that allow very fast communication between the muscle cells, including intercalated discs, or gap junctions, that connect each cell together, allowing for very rapid transfer of ions between the muscle cells. Neurotransmitter molecules interact with muscle cell membrane molecular receptors at the neuromuscular junction, or synapse, eliciting a series of cellular events leading to shortening and contraction of the muscle cells. When many muscle cells contract, the organ or tissue containing the muscle cells shortens, allowing movement to occur, such as limb motion, intestinal motility, or gallbladder contraction.