Locomotion : It is the act of movement which includes walking, running, crawling, hoping, flying or swimming freely, either on land or in liquid or in gaseous medium.
Movement : It refers to the act of certain parts of the body in a particular direction.
Types of muscle fibres
(i) Skeletal muscle fibres.
(ii) Smooth muscle fibres.
(iii) Cardiac muscle fibres.
Various modes of locomotion in hydra
(i) Somersaulting
(ii) Looping.
Skeletel System : It consists of a set of bones present in the body.
A human skeleton consists of a total of 206 bones.
Joint : A joint is a point where two or more bones are fitted to one another.
Ligaments : These are flexible connective tissue bonds which stabilise the joints by holding the articulating bones together.
Arthritis : It is a disease of joints due to the following reasons :
(i) Lack of synovial fluid
(ii) The ossification of articular cartilage
(iii) Deposition of uric acid crystals in synovial cavity.
Slipped Disc : Slipped disc is the displacement of vertebrae from their normal position in the vertebral column.
Dislocation : If the bones at the joints are dislodged from their correct positions, this is called dislocation.
Fracture : This is the break in the bone.
Parts of skeletal system
(i) Axial skeleton : It is made up of skull, vertebral column, stemum and ribs. The total number of bones in it are 80.
(ii) Appendicular skeleton : It consists of the girdles and limbs. The total number of bones in it are 127.
Muscle fatigue : If a muscle is subjected to a prolonged stimulation, there is a drop in the force of contraction of muscle which is known as muscle fatigue.
Poliomyelitis : It is a serious disease in which the muscle weakness prevails due to the polio virus.
Threshold stimulus : For being stimulated to contract, the muscle fibre always requires a specific minimum strength or intensity of stimulus. This is called threshold stimulus of muscle fibre.
All or none law : If the stimulus has a strength equal to or higher than threshold stimulus, the muscle fibre contracts with maximum force irrespective of the strength of the stimulus. The force of contraction does not rise in such a case on increasing the strength of the stimulus. This is known as all-or-none law.
Muscle Twitch : A muscle fibre contracts only once if it is stimulated by a single nerve impulse or electric shock of sufficient strength. This single isolated contraction of muscle fibre is called muscle twitch.
Tension : Tension is the force exerted by the contracting muscle on the weight when it is lifted by the muscle.
Load : Load is the force exerted by the weight on the muscle.
Summation : When a muscle is stimulated by two successive stimuli even before the muscle has relaxed from first stimulus. The response of the second stimulus will be more than first—and this increased response due to the second stimulus is known as summation.
Tetanus : Tetanus is the response of the muscle by a series of stimuli continuously. In this second stimulus is given even before the muscle has relaxed from first and the third stimulus is given even before the muscle has relaxed from second and so on. Such a response of muscle is called tetanus.
Rigor Mortis : It is a kind of disorder in which the body muscle becomes stiff and rigid due to non-availability of ATP molecules, enzymes and oxygen. Under this condition, if the muscle is stimulated it will not show any response. It finally makes the muscle die.
Coris’s Cycle : This cycle involves many steps that take place in muscles and liver. The major steps of coris’s cycle are:
¾Muscle glycogen¾
¯
Muscle lactic acid Blood actic acid
¯
Blood lactic acid ® Liver ¾
Liver glycogen
1/5 Oxidised to CO2 and H2O
Isotonic contraction : In isotonic contraction of muscle the load remains constant throughout the period of shortening of muscle.
Isometric contraction : In this further contraction is prevented by putting weight at constant length of the muscle, it is known as isometric contraction.
Tendon : Tendon is a tough cord or a band of dense fibrous connective tissue which unites a muscle with a bone.
A tendon is not contractile.
Aponeurosis : An expanded tendon having a fibrous or membranous sheet is called aponeurosis.
Denervation atrophy : If any damage is done to the nerve cells, a decrease in the size of muscle takes place, which causes paralysis of the muscle. This condition of muscles is called denervation atrophy.
Disuse atrophy : Disuse atrophy condition is realised in muscles which are not used for a long time.
Poliomyelitis : In poliomyelitis, polio virus weakens the body muscles, particularly of legs and forearms.
Muscular hypertrophy : If the muscle fibre of an adult is damaged, it cannot be replaced through a cell division of surviving muscle tissue. However the surviving cells can increase their size by synthesizing myofibrils in each cell. This increase in the size of individual muscle fibre is known as muscular hypertrophy.
Duchenne dystrophy : It is a disease of muscle where the muscle itself is damaged. In poliomyelitis the muscle gradually weakens due to infection by polio virus.
Locomotion in different animals : Most of the animals are provided with the locomotory organs according to their requirements. Main types of locomotion are as follows—
1. In acellular animals
(i) Amoeboid locomotion : By protoplasmic pseudopodia.
(ii) Ciliary locomotion : By cilia which are present on the total body surface.
(iii) Flagellar locomotion : One or two flagella attached to the basal granule.
2. Locomotion in Hydra : Body wall of Hydra contains the muscular cells which perform the following locomotion :
(i) Gliding
(ii) Swimming
(iii) Somersaulting
(iv) Looping movement
(v) Cuttle fish like
(vi) Climbing
3. Locomotion in annelids : Mainly they are provided in every segment with the seatae. These seatae are controlled by the body wall muscles.
4. Locomotion in insects : Insects move with the help of legs and appendages. Pterygots have wings which help them in flying.
5. Locomotion in fishes : For locomotion they are provided with fins and muscles. Tail also helps the fish in locomotion. In exocoetus fish, the fins become broad and help the fish in gliding in air for a short duration. e.g. flying fish.
6. Locomotion in amphibians : Tadpole locomote like fish whereas adult swims in water and walks and jumps on the earth.
7. Locomotion in reptiles : Except snakes the movement in reptiles is by creeping with the help of legs. The wall lizards are provided with cup like pads. In these pads vacuum is developed when the lizard walks and run over walls. The snakes are not provided with legs but move with the help of ribs and scales.
8. Locomotion in birds : Birds have wings for flying. The light muscles are very well-developed.
9. Locomotion in mammals : Generally in mammals the locomotion and movements are performed by the skeletal system and muscles. Most of the mammals are provided with two pairs of legs. In flying mammals forelegs are modified into wings.
10. Locomotion in man : The movement in man is very much similar to other mammals. The skeleton is made movable by joints and the movements are with the contraction and relaxation of muscles. Thus the movement may be voluntary or involuntary. The muscles attached with the skeletal system are known as skeletal muscles.
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