Movements and Locomotion

Movements may be internal (e.g. protoplasmic streaming, peristalsis, heartbeat) or external (e.g. limb movement), and they may be voluntary or involuntary. Three types of muscle tissue bring about movements in humans:

• Smooth muscle — involuntary movements such as peristalsis in the alimentary canal and constriction/dilation of blood vessels.
• Cardiac muscle — the contraction and relaxation of the heart.
• Striated (skeletal) muscle — voluntary movements of the limbs, head, trunk, eyes, etc.

Locomotion is the change in position of the whole body of an organism from one place to another, undertaken in search of food, shelter, a mate, or breeding grounds, or to escape a predator. Four basic types of locomotory movement are seen across the animal kingdom:

1. Amoeboid movement — brought about by pseudopodia, e.g. leucocytes.
2. Ciliary movement — brought about by cilia, e.g. ciliated epithelium; in Paramecium, cilia move food through the cytopharynx.
3. Whorling (flagellar) movement — brought about by flagella, e.g. sperm.
4. Muscular movement — brought about by muscles acting together with bones and joints.

Remember: all locomotion is movement, but not all movement is locomotion.

Skeletal muscles attach to bones through tendons — inelastic, thick bands of collagen fibres — and move parts of the skeleton. Movement and locomotion are thus the combined action of bones, joints and skeletal muscles.