Muscular

• Movement


  Any change in body position. It is a fundamental characteristic of living beings
• Locomotion


  The movement of body parts that leads to change of place
• Amoeboid movements


  • Occur with the help of pseudopodia
• Ciliary movements


  • Occur with the help of cilia, e.g. movement of trachea in removing waste
• Flagellar movement


  • Takes place with the help of flagella, e.g. movement of sperms in water
• Muscular movements


  • Involve muscular tissues, e.g. movements in vertebrates including humans
• Types of muscles based on location

  • Visceral muscles (smooth and involuntary, e.g. muscles of heart)
  • Skeletal muscles (striated and voluntary)
• Skeletal muscle


  Composed of elongated muscle fibres called muscle fibres that remain covered by sarcolemma
• Skeletal muscle structure

  • Sarcoplasm (watery fluid) containing sarcoplasmic reticulum (ER of muscles)
  • A-band, H-zone, M-line, I-band, Z-line
  • Sarcomere (unit of contraction)
• Myofibrils


  Composed of myofilaments made up of myosin, actin, tropomyosin and troponin
• Thick myofilaments

  • Consist of myosin protein composed of 4 heavy and 2 light chains
• Muscle contraction

  1. Signal reaches neuromuscular junction

  2. Vesicles with neurotransmitters fuse with cell membrane and release acetylcholine

  3. Action potential generated in sarcolemma

  4. Ca2+ released into sarcoplasm

  5. ATPase catalyses ATP to ADP+P

  6. Myosin-actin crossbridges form, thin filaments slide over thick filaments, sarcomere shortens
• Muscle relaxation

  1. Acetylcholinesterase breaks down acetylcholine

  2. Action potential retarded

  3. Crossbridges not formed
• Parts of human skeletal system

  • Axial skeleton (skull, vertebral column, ribs, sternum)
  • Appendicular skeleton (forelimbs, hindlimbs, pectoral girdle, pelvic girdle)
• Types of joints

  • Fibrous joints (no movement, e.g. skull sutures)
  • Synovial joints (considerable movement, e.g. ball and socket, hinge, pivot, gliding, saddle)
• Arthritis is the inflammation of joints that is common in old age people. It includes pain and stiffness in joints
• Gout is an inherited disorder of purine metabolism that occurs especially in men
• Osteoporosis is the reduction in bone tissue mass that causes weakness in skeletal strength
• Myasthenia gravis is an autoimmune neuromuscular disorder leading to fluctuating muscle weakness and fatiguability
• Tetany causes muscle to undergo a smooth sustained contraction as relaxation cannot occur between successive contractions
• Muscular dystrophy is a genetic disorder characterised by progressive skeletal muscle weakness, defects in muscle protein, etc