SUMMARY
All living things must move in order to survive. Animals display a variety of behaviours, including protoplasmic streaming, ciliary motions, movements of the fins, limbs, wings, etc. Locomotion is a voluntarily performed movement that causes an animal to shift its position. Generally speaking, animals travel in order to find food, shelter, a mate, a breeding place, a better environment, or to protect themselves.
The human body's cells display amoebic characteristics. Muscular and ciliary motions Movements such as walking and many others involve coordinated muscle actions. Our body contains three different kinds of muscles. Skeletal components are connected to skeletal muscles. They have a striated appearance and are purely voluntary. They appear striated and are voluntary in nature Visceral muscles, present in the inner walls of visceral organs are nonstriated and involuntary. Cardiac muscles are the muscles the heart. They are striated, branched and involuntary. Muscles possess excitability, contractility, extensibility and elasticity.
Muscle fibre is the anatomical unit of muscle. Each muscle fibre has many parallelly arranged myofibrils. Each myofibril contains many serially arranged units called sarcomere which are the functional units Each sarcomere has a central A band made of thick myosin filaments, and two half T bands made of thin actin filaments on either side of it marked by Z lines. Actin and myosin are polymerised proteins with contractility. The active sites for myosin on resting actin filament are masked by a protein troponin Myosin head contains ATPase and has ATP binding sites and active sites for actin. A motor neuron carries signal to the muscle fibre which generates an action potential in it. This causes the release of Ca" from sarcoplasmic reticulum. Ca" activates actin which binds to the myosin head to form a cross bridge. These cross bridges pull the actin filaments causing them to slide over the myosin filaments and thereby causing contraction. Ca" are then returned to sarcoplasmic reticulum which inactivate the actin. Cross bridges are broken and the muscles relax.
Repeated stimulation of muscles leads to fatigue. Muscles are classified as Red and White fibres based primarily on the amount of red coloured myoglobin pigment in them.
Bones and cartilages constitute our skeletal system. The skeletal system is divisible into axial and appendicular Skull. vertebral column, ribs and sternum constitute the axial skeleton. Limb bones and girdles form the appendicular skeleton. Three types of joints are formed between bones or between bone and cartilage - fibrous, cartilaginous and synovial Synovial joints allow considerable movements and therefore, play a significant role in locomotion.
