Locomotion

• Animals and plants exhibit a wide range of movements
• Streaming of protoplasm in unicellular organisms like Amoeba is a simple form of movement
• Movement of cilia, flagella, and tentacles are shown by many organisms
• Human beings can move limbs, jaws, eyelids, tongue, etc
• Voluntary movements that result in a change of place or location are called locomotion
• Walking, running, climbing, flying, swimming are forms of locomotory movements
• Locomotory structures may not be different from those affecting other types of movements
• All locomotions are movements but all movements are not locomotions
• Cells of the human body exhibit three main types of movements: amoeboid, ciliary, and muscular
• Specialised cells like macrophages and leucocytes exhibit amoeboid movement
• Ciliary movement occurs in internal tubular organs lined by ciliated epithelium
• Muscular movement is required for movements of limbs, jaws, tongue, etc
• Muscle is a specialised tissue of mesodermal origin
• About 40-50% of the body weight of a human adult is contributed by muscles
• Muscles have special properties like excitability, contractility, extensibility, and elasticity
• Three types of muscles based on location are: Skeletal, Visceral, and Cardiac
• Skeletal muscles are striated, under voluntary control, and primarily involved in locomotory actions and changes of body postures
• Visceral muscles are smooth in appearance, not under voluntary control, and assist in functions like transportation of food and gametes
• Each muscle fibre is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm
• The sarcoplasm contains many nuclei, and the sarcoplasmic reticulum is the storehouse of calcium ions
• Myofibrils contain actin and myosin, giving a striated appearance to muscles
• Cardiac muscles are striated and involuntary, forming the muscles of the heart
• Muscle contraction is explained by the sliding filament theory, where thin filaments slide over thick filaments
• Muscle contraction is initiated by a signal from the central nervous system via a motor neuron
• The mechanism of muscle contraction involves the binding of myosin to actin, forming a cross bridge and shortening the sarcomere
• Muscles can be classified as Red fibres (aerobic) with high myoglobin content and White fibres (anaerobic) with less myoglobin content
• The skeletal system consists of a framework of bones and a few cartilages
• The skeletal system plays a significant role in movement in the body
• Bone and cartilage are specialised connective tissues
• The skeletal system in human beings is made up of 206 bones and a few cartilages
• The skeletal system is grouped into two principal divisions - the axial and the appendicular skeleton
• The axial skeleton comprises 80 bones distributed along the main axis of the body
• The skull, vertebral column, sternum, and ribs constitute the axial skeleton
• The skull is composed of two sets of bones - cranial and facial, totaling 22 bones
• The facial region is made up of 14 skeletal elements which form the front part of the skull
• The middle ear contains three tiny bones - Malleus, Incus, and Stapes, collectively called Ear Ossicles
• The vertebral column is formed by 26 serially arranged units called vertebrae and is dorsally placed
• The vertebral column is differentiated into cervical (7), thoracic (12), lumbar (5), sacral (1-fused), and coccygeal (1-fused) regions starting from the skull
• The sternum is a flat bone on the ventral midline of the thorax
• There are 12 pairs of ribs, with the first seven pairs called true ribs