T3.7 muscular system

• Muscle tissue

  Specialised cells that have ability to contract and shorten when stimulated
• Muscle tissue

  • Contraction is an active process during which chemical energy is changed into mechanical energy
  • Functions: producing body movements, stabilising body positions, moving materials within the body, regulating organ emptying, producing heat
• Muscle tissue types


  • Skeletal muscle - long cylindrical striated fibres
  • Cardiac muscle - short striated fibres
  • Smooth muscle - non striated
• Primary functions of skeletal muscle

  • Move or prevent movement of skeleton of limbs & vertebral column
  • Maintain posture & body position and stabilise joints
  • Create facial expression, movement of the eyeballs
  • Enable speech, chewing and swallowing
  • Enable blood flow ('muscle pump')
  • Protect underlying structures
  • Generate heat during contraction
• Skeletal muscle fibres

  • Up to 30cm long, cylindrical and multinucleated
  • Mature muscle cells cannot divide - muscle growth is a result of cellular enlargement
• Sarcolemma

  Muscle cell membrane
• Sarcoplasm

  Cytoplasm of muscle cell, filled with myofibrils and mitochondria
• Myoglobin

  Red-coloured, oxygen-binding protein for oxygen storage; similar to haemoglobin
• Glycosomes

  Small vesicles for glycogen storage
• Myofibrils

  Tiny threads made up of myofilaments (actin and myosin proteins)
• 1. tubules

  Infoldings of the sarcolemma into the centre of the cell, filled with interstitial fluid; carry action potentials closer to the sarcoplasmatic reticulum
• Mitochondria

  For energy production, lie in rows throughout the cell
• Sarcoplasmatic reticulum

  System of tubular sacs similar to smooth endoplasmatic reticulum in regular cells
• Neuromuscular junction

  Interface between motor neuron and muscle cell
• Motor unit


  • One lower motor neuron and all skeletal muscle fibres it innervates
  • Motor unit size varies, small units for fine control, large units for powerful contractions
• Muscle contraction


  1. Electrical signal travels down motor neuron

  2. Signal crosses neuromuscular junction

  3. Muscle cell contracts
• Creatine phosphate

  Energy rich molecule produced from excess of ATP, found only in muscle fibres
• Glycolysis

  Anaerobic breakdown of glucose without oxygen, produces lactic acid
• Aerobic cellular respiration

  Uses glucose, fatty acids and amino acids, produces much more energy than glycolysis
• Muscle fibre

  Skeletal muscle cell
• Tendon

  Dense regular connective tissue that connects muscle to bone
• Deep fascia

  Additional, expansive sheet of dense irregular connective tissue, external to epimysium, often blends with it
• Sarcolemma

  Plasma membrane of a muscle cell
• 1. tubules

  Deep invaginations of sarcolemma
• Myofibrils


  Bundles of myofilaments within skeletal and cardiac muscle cells
• Sarcoplasmic reticulum

  Endoplasmic reticulum found in muscle cells; stores calcium ions required for contraction
• Myofilaments (thick and thin)

  Protein filaments that make up the myofibrils in both skeletal and cardiac muscle cells
• Sarcomeres

  Functional unit of skeletal muscle
• Motor unit


  One neuron and all skeletal muscle fibres it innervates
• Neuromuscular junction

  Relationships between a neuron and a muscle cell