Support And Movement In Man – Key Points
Support in man; woody and non-woody parts of plant is due to skeleton; various mechanical tissues and presence of water in their parenchymatous cells besides cylindrical distribution of conducting tissues respectively.
Movement is response shown by a part of living organism towards or away from the stimulus while locomotion refers to the movement of whole organism from one place to another under the influence of stimulus.
Supporting tissues of woody dicotyledonous stem is due to the secondary growth or thickening. This gives rice wood and bark from the activity of vascular cambium and cork cambium respectively.
Movement of plant body as a whole is known as tactic movement. The movement of parts of plant towards or away from the stimulus is known as positive and negative tropism. The stimulus in this case is only from one direction.
Tropism may be of three types; Geotropism, phototropism and Hydrotropism, the response is due to stimuli, force of gravity, light and water respectively.
Nastic movements in parts of the plants are affected by a stimulus from all directions e. g. folding and unfolding of buds or leaves.
Geotropism and phototropism are caused by a growth regulating substance or hormone called auxin.
Investigations proved that auxins produced by the root and shoot apices caused the growth responses below these apices.
Locomotion in Euglena is by a single whip like flagellum while that of Volvox by simultaneous action of flagella of all the cells of colony.
Locomotion of movement in Amoeba is brought about by the flow of cytoplasm in finger like processes, pseudopodium. Paramecium moves with the help of cilia.
Skeleton in man is of two types: axial and appendicular. It supports the body and helps to produce movements with the help of muscles.
Muscles play an important role in the support of skeleton and responsible for the movements of parts of parts of the body.
Action of biceps (flexor) and triceps (extensor) brings about bending and straightening of the limb and is known as antagonistic movement of the forearm.
Tendons attach each end of the muscle to the skeleton while the relevant bones of the joints are held together by ligaments.
Elbow joint acts like a lever with the low mechanical advantage.
Ball and socket joints of shoulder and hip allow movement in three directions, forward, backwards and sideways. The hinge joints of elbow and knee allow movement in only one plane.
Defects of skeletal system may be due to changes in bones and joints in old age causing diseases osteoporosis and osteoarthritis respectively.
Dislocation of joint is the displacement of one or more bones at a joint.