Support and movement 💪🦵

• Muscle fatigue


  Refractory period
• Muscle fibres


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• Movement


  The act of changing position or place by the entire body of an organism or by one or more of its parts
• Kinesiology


  The study of movements
• Levels of movement

  • Molecular
  • Cellular
  • Organ
  • Organism
• Brownian movement


  Zig-zag motion of molecules in the cytosol
• Cyclosis


  Streaming movement of cytoplasm
• Amoeboid (Pseudopodial) movement


  Temporary protoplasmic outgrowths called pseudopodia
• Ciliary movement


  Movement of cilia to propel dust particles, ova and sperm
• Flagellar movements


  Movement of flagella to generate water currents and circulate fluid
• Types of movement


  • Nonmuscular
  • Muscular
• Muscular movements


  Produced by the action of muscles, responsible for locomotion and movement of body parts
• Advantages of movements to animals

  • Movements of external body parts
  • Movements of internal body parts
  • Movements within cells
• Locomotion


  Movement of an organism as a whole resulting in change of place
• Types of locomotion

  • Walking
  • Running
  • Hopping
  • Somersaulting
  • Creeping
  • Crawling
  • Flying
  • Swimming
  • Gliding
• Organisms with ability to move are called motile
• Purposes of locomotion


  • Escape from enemies
  • Search and procure food and water
  • Move from unfavourable environment
  • Find mate
  • Find shelter and suitable place for laying eggs
  • Migrate to new areas
• Muscle


  Specialised tissue of mesodermal origin, constitutes 40-50% of human body weight, formed of muscle fibres or myofilaments
• Types of muscles


  • Voluntary or Skeletal or striated
  • Involuntary or Smooth or nonstriated or visceral
  • Cardiac
• Skeletal or striated muscles (Voluntary muscles)

  Form body flesh and about 80% of soft body tissue, found in limbs, body wall, tongue, pharynx and beginning of oesophagus, work under voluntary control
• Skeletal muscles


  • Enclosed in dense connective tissue sheath called epimysium, formed of muscle bundles called fasciculi, each fasciculus formed of muscle fibres covered in endomysium
• Myofibril


  Composed of serially repeated sarcomeres
• Muscle fasciculi (muscle fasicles)


  • Numerous small muscle bundles, each with a connective tissue covering (perimysium)
• Muscle fibre (muscle cell)

  • Covered with endomysium formed of loose connective tissue
  • Blood vessels and nerves run between the muscle fibres
  • At the junction of a muscle with a tendon, the endomysium, perimysium and epimysium are continuous with the fibres of the tendon
• Each muscle fasiculum is formed of several muscle fibres
• All the sheaths (endomysium, perimysium and epimysium) are formed mainly of yellow elastic tissue
• Sarcolemma


  The membrane of a muscle fibre
• Muscle fibre (muscle cell)


  • Unbranched, cylindrical, 10-100 μm in diameter
  • Contains multiple nuclei (multinucleate)
• Sarcoplasmic reticulum


  Network of interconnected tubules and sacs that surround each myofibril
• Myofibril


  • Composed of serially repeated sarcomeres (the unit of contraction) separated by Z-discs
  • Contains two types of myofilaments: actin and myosin
• Sarcomere


  The unit of contraction in a muscle fibre
• Sarcomere


  • Formed of two types of myofilaments: actin (thin) and myosin (thick)
  • Actin filaments are located in I-bands and extend into A-bands
  • Myosin filaments are located in A-bands
  • H-zone is the central part of A-band without actin filaments
• Actin


  Contractile protein that forms thin filaments, made up of globular G-actin molecules
• Myosin


  Contractile protein that forms thick filaments, made up of two heavy chains and four light chains
• Myosin


  • Globular head with ATPase activity and actin binding site
  • Rod-like tail
• Tropomyosin


  Regulatory protein that lies in the groove between actin filaments, covering the myosin binding sites
• Troponin


  Regulatory protein that binds to actin and tropomyosin, preventing myosin binding
• Muscle contraction (Sliding Filament Theory)

  1. Actin filaments slide towards the H-zone between myosin filaments

  2. H-zone disappears and I-band width reduces

  3. Sarcomere shortens, causing muscle contraction
• Muscle contraction requires: 1) Nervous stimulus, 2) ATP, 3) Ca2+ ions
• Resting potential


  Polarised state of the sarcolemma, with outer surface positively charged relative to inner surface