There are 3 types of
muscle tissue. These differ in the speed, duration and effects of their
contractions. In the
structure of their fibres. And finally, in the tasks they are required to perform. The three kinds of muscle are:
- Cardiac muscle - Cardiac muscle forms the walls and partitions of the heart, and this muscle tissue contracts rhythmically to squeeze blood into the arteries. This is a special, regular long term job. Imagine having to clench and unclench your fist 72 times a minute, day and night, for the whole of your life. Fortunately, we don't have to remember to contract our cardiac muscle. The action is involuntary, we cannot choose to prevent it from contracting, and neither can we consciously make it contract.
- Smooth muscle - May also be called visceral or involuntary muscle and is to be found in the walls of the internal (visceral) organs, except for the heart. Examples are the intestines, blood vessels and stomach.
This kind of muscle consists of slender, spindle-shaped cells, which are tapered toward both ends. Whereas cardiac and skeletal muscle cells are striated, smooth muscle cells are not striped. Another difference is that smooth cells are much smaller than those found in most skeletal muscles: they are between 0.26 and 0.05 millimetres long.
Compared with skeletal muscle, smooth muscle is:
- more elastic
- more sensitive to temperature changes and chemical stimuli
- able to sustain contractions for longer periods
- slower to contract
- Skeletal muscle - The skeletal muscles are the ones under conscious control, and they're the only type to play a significant role in voluntary body movement. Skeletal muscle contains several types of fibre. Some fibres are labelled fast-twitch, and others slow-twitch, although other fibres operate between these two extremes. The fast fibres contract more quickly and develop more tension than slow fibres, but sow fibres have greater endurance.