Movement is the characteristic of all living beings. Movement can be at cellular level, organ level or there can be movement of the entire body. The movement of entire body is known as locomotion.
Amoeba / Entamoeba move with the help of pseudopodia. Paramecium moves by cilia.The movement of sperms occurs by fl agellum (enlarged version of cilium) or tail.
The movement of macrophages and leucocytes (WBCs) are cellular movements in higher animals.
The movement of body parts (called Kinesiology) includes- movement of jaws, eyeball, gut (peristalsis), heart, lungs (breathing), limbs and appendages etc.
The locomotion enables the animals to shift the entire body from one place to another. The running, jumping, crawling, fl ying and swimming etc. are such locomotory movements. The plants do not show locomotion (except few lower plants) but move body parts by phototropism or Geotropism.
The important advantages of locomotion are
• For procuring nutrition.
• For avoiding unfavourable conditions.
• For shelter.
• For defending from predators.
• For searching mating - partners.
Survey of locomotory structures in different animal groups -
• In Porifers the animals are sessile and there are no locomotory structures. Only larvae are free swimming.
• In Coelenterates the tentacles are present for movement. The epidermis and gastrodermis also have epithelio- and endothelio muscular cells for locomotory movements, like somersaulting and looping etc.
• In Annelids the longitudinal and circular muscles are differentiated and the animal moves either with the help of Parapodia (Neries) or Setae (earthworm). The locomotory structure in leech is posterior sucker. The coelomic fl uid in these animals acts as a hydrostatic skeleton.
• In Arthropods, the jointed appendages, and in molluscs, the foot is used for locomotion.
The chitin in arthropods forms exoskeleton and provides support to the muscles.
• In Echinoderms tthee waatteer vaasccullaar systteemm (Ambulacral system) is utilized by tube feet for locomotion.
• In Vertebrates the locomotion is with the help of skeletal muscles associated with the endoskeleton of limbs.
STRUCTURE OF BICEP (SKELETAL) MUSCLE
• The outermost – connective tissue covering of muscle is called Epimysium. The Epimysium surrounds many bundles of muscle fi bres.
• Each bundle of muscle fi bre, called fasciculus, is surrounded by another connective tissue covering called Perimysium.
• Inside fasciculus there are several muscles fi bres, each surrounded by connective tissue covering called Endomysiun.
Structure of Muscle fibre
• In ordinary light there appear alternate dark and light transverse bands in the muscle fi brils.
The width of dark band is ~1.5μ and the width of light band is ~ 0.8μ .
• In polarized light the dark band is Anisotropic, so called A-band, whereas the light band is Isotropic, so called I-band.
• The dark band (A-band) in the centre contains outer H-band and inner M-band.
• The light band (I-band) in the centre contains a Zig-Zag line/band, called Z-band or Krause membrane.
• The distance between two adjacent Z-bands/ Krause membranes is called Sarcomere.
• The Sarcomere is the functional unit of muscular tissue. It includes 1 A-band and 2- halves of I-band.
A-band
• It contains thick as well as thin protein fi laments.
• The diameter of thick fi laments is more than the diameter of thin fi laments.
