Muscular skeletal system

• Skeletal system


  The framework for the human body
• Skeletal system


  • Bases for attachment of muscles and tendons
  • Provides minerals (calcium and phosphates)
  • Protection for vital organs: Heart and Lungs: ribcage and sternum
  • Produces blood elements: (RBC's and WBC's): Red bone marrow – center of bone
• Bones in the human body

  • Axial skeleton (74 bones)
  • Appendicular skeleton (126 bones)
  • Total is 206 bones!
• Ligament


  Connective tissue that holds bones together
• Joint (articulation)


  Where two bones meet
• Types of joints


  • Immovable
  • Glide
  • Pivot
  • Hinge
  • Ball-socket
• Bone composition


  Primarily composed of calcium and phosphate
• Classifications of bones by shape

  • Short Bones
  • Long Bones
  • Flat Bones
  • Irregular Bones
  • Sesamoid
• Short bones


  • Cubelike, no medullary cavity, mostly spongy bone tissue with thin compact bone crust
• Long bones


  • Have a shaft (diaphysis) and two expanded ends (epiphysis)
  • Consist of a medullary cavity
• Flat bones


  • Thin, platelike, no medullary cavity, outer layers of compact bone with spongy bone in between
• Irregular bones


  • Odd shaped, no medullary cavity, mostly spongy bone tissue with thin compact bone crust
• Structures of bone


  • Periosteum
  • Compact Bone
  • Spongy (Cancellous) Bone
  • Marrow (Red and Yellow)
• Muscle


  Soft tissue that contains protein filaments of actin and myosin that slide past one another, producing contraction and movement
• Muscle types


  • Smooth
  • Cardiac
  • Skeletal
• Smooth muscle


  • Fusiform cells with 1 nucleus, located on walls of hollow structures, non-striated, involuntary action, slow wave-like contractions, regulated by ANS neurons and hormones
• Cardiac muscle


  • Striated & branched fibres, 1/2 nuclei/cell, located only in heart wall, involuntary action, contraction speed < skeletal but > smooth, built-in "electrical pacemaker" for activity, controlled by hormones and neurotransmitters
• Skeletal muscle


  • Fibres long & cylindrical, many nuclei/cell, attached to most bones, striated, fastest of the muscle types, voluntary control by somatic neurons, subconscious control to a lesser degree
• Fusiform muscle


  Muscle belly fibres are arranged parallel to each other
• Cardiac muscle


  Striated muscle present only in the heart, fibres have a single nucleus, are branched, and joined by intercalated discs
• Myofibrils


  Long cylindrical structures within muscle fibres that run the entire length and contain the contractile proteins
• Functional characteristics of muscles


  • Excitability, Contractility, Extensibility, Elasticity
• Muscle contraction


  1. Nervous impulse travels through muscle plasma membrane

  2. Muscle generates pulling force

  3. Muscle can be stretched back to original length by opposing muscle action

  4. Muscle passively recoils to resume resting length
• Smooth muscle types


  • Single unit
  • Multi-unit
• Single unit smooth muscle

  • Found in skin and lining of hollow organs, has auto rhythmicity (involuntary action), cells are fusiform and joined by gap junctions, contracts as a whole
• Multi-unit smooth muscle


  • Found in large arterial walls, respiratory tract and ciliary body, fusiform cell shape but only a few gap junctions, individual fibres with own neurone terminals, activation of a single fibre will result in contraction of that fibre alone
• Muscle protein types


  • Structural
  • Contractile
  • Regulatory
• Sliding filament mechanism


  Muscle contraction is brought about as the thick & thin filaments slide over/past each other
• Muscle contraction


  1. Muscle action potential originates at neuromuscular junction

  2. Release of acetylcholine (ACh) into synaptic cleft

  3. ACh binds to receptors on motor end plate and opens ion channels

  4. Increased flow of Na+ into muscle cell changes membrane potential and initiates muscle action potential

  5. Muscle action potential travels along sarcolemma into T-tubule system

  6. ACh effect terminated by acetylcholinesterase (AChE) which degrades ACh
• Motor unit


  Single motor neuron axon and all the muscle fibres it controls