BRIEF INTRODUCTION ON MOVEMENT AND SUPPORT

The act of changing position from one place to another is called as movement. In biology, we differ between locomotion and movement. Locomotion is actual type of movement in which an organism fully moves from one place to another in search for food, etc while movement refers to moving one limb or branch of leaves or any other thing towards or away from stimulus. In biology, movement can occur at:

• Cell level, for example cytoplasmic streaming and swimming of gametes:
• Organ level, such as heartbeat and movement of a limb;
• The level of the organism

Movement of the whole organism from place to place is termed locomotion. Plants show cell and often organ movement, but they do not show locomotion, that is moving from one place to any other place in search of food or water. Movements are induced by external stimuli and fall into two main categories: Tropisms (tropic movements) and Taxes (tactic movements). A few animals can survive successfully by remaining attached to one place (sessile), the vast majority have locomotory systems which presumably evolved to enable them to search for and acquire food. However, even sessile animals exhibit a great degree of mobility of their bodily parts. Locomotion is used for:

• Finding food 
• Avoiding capture by predators 
• Finding new and favorable habitats 
• Bringing together individuals for reproductive activity.

Locomotion involves coordination between the nervous, muscular and skeletal systems.

Muscle tissue is composed of long excitable cells capable of considerable contraction. Arranged in parallel within the cytoplasm of muscle cells are large in number of microfilaments made of the contractile proteins actin and myosin. Consistent with a high priority on movement, muscle is the most abundant tissure in most animals, and muscle contraction accounts for much of the energy consuming cellular work in an active animal.

Skeletal Muscle

In vertebrate body, there are three types of muscle tissues: skeletal muscle, cardiac muscle, and smooth muscle. Attached to bones by tendons, skeletal muscles are generally responsible for the voluntary movements of the body. Adults have a fixed number of muscle cells; weight lifting and other methods of building muscle do not increase the number of cells but simply enlarge those already present. Skeletal muscles are also called striated muscles because the arrangement of overlapping filaments gives the cells a striped i.e. striated appearance under the microscope.

Cardiac Muscle

Cardiac muscles are present in the heart and form the contractile wall of the heart. It is striated like skeletal muscle, but cardiac muscle cells are branched and the ends of the cells are joined by structures called intercalated discs, which relay signals from cell to cell during a heartbeat.

Smooth Muscle

Smooth muscles, so named because it lacks cross-striations, are found in the walls of the digestive tract, bladder, and other internal organs. The cells are spindle-shaped. They contract more slowly than skeletal muscles, but they can remain contracted longer. Skeletal and smooth muscles are controlled by different kinds of nerves. Skeletal muscles are often called voluntary because an animal can generally contract them at will. Smooth muscles are often involuntary; they are not generally subject to conscious control. You can decide to raise your hand, but you are usually unaware when smooth muscle churn your stomach or constrict your arteries.