The three types of muscle found in the human body are skeletal, smooth, and cardiac muscle.
Skeletal muscles attach to bones. Their main function when they contract is the movement of the skeleton. Sometimes we call skeletal muscle types striated muscle. This is because of their striped appearance caused by bands of Actin and Myosin in the muscle.
Another name for skeletal muscles is voluntary muscles. This is because we have direct control over them through nervous impulses. Our brains send messages to the muscles to make them move.
The contraction of skeletal muscle types varies. They are capable of very powerful, fast movements or small precision actions. Skeletal muscles also have the ability to stretch or contract and still return to their original shape.
Not all skeletal muscle fibres are the same. Different skeletal muscle fibre types contract at different speeds. As a result, they suit different activity types. They vary in colour depending on myoglobin (an oxygen-carrying protein) content. The three types of skeletal muscle fibres are Type one (I), type two A (IIa), and type two B (IIb).
The walls of the stomach, oesophagus, bronchi, and blood vessels contain smooth muscle. Out of the three types of muscle smooth muscle only contracts involuntarily. In other words, it contracts automatically without us consciously telling it to.
Smooth muscle contracts slowly and rhythmically to control internal organs. For example, when food moves along the oesophagus or when blood vessels constrict to reduce blood flow. Smooth muscle is also called Involuntary or unstriated muscle. It does not appear striped like skeletal muscle.
Cardiac muscle (heart muscle)
Of the three types of muscle, only the heart contains cardiac muscle. Its striated appearance makes it similar to skeletal muscle. However, it also contracts involuntarily like smooth muscles.
Cardiac muscle is highly specialised. It is under the control of the autonomic nervous system. However, even without a nerve stimulating it, it still contracts due to cells called pacemaker cells.
Cardiac muscle is very resistant to fatigue. This is because of the large number of mitochondria, myoglobin, and a good blood supply. As a result, continuous aerobic metabolism is possible.