Musculoskeletal system

• Ligaments


  • Connect bones to bones
• Cartilage


  'shock absorbing' gel between joints
• Tendons


  • Connect muscles to bones
  • Achilles Tendon
• Functions of Skeletal System

  • Protects vital internal organs such as the brain, spinal cord and lungs
  • Support - allowing proper posture to be maintained
  • Stores fuels, fats, and minerals
  • Allows for movement through attachment sites
  • Mineral Balance/Homeostasis
  • Blood cell production
• Appendicular Skeleton


  Includes all of the bones outside the midline, including the arm, hand, leg, foot, shoulder girdle and pelvic girdle
• Axial Skeleton


  Includes all of the bones in the midline, including the Skull, Chest, and Vertebral Column
• The spinal column consists of 5 sections: Cervical (7), Thoracic (12) Lumbar (5) Sacrum (5 fused) Coccyx (4 fused)
• Vertebral Column


  • Protects the spinal cord as well as the heart and lungs
  • Cartilage discs separate the first three sections
• Types of Bones


  • Short bones - cubical and have the same height and width e.g. carpals and tarsals
  • Long bones - longer than wide e.g. the femur and radius
  • Sesamoid bones - developed in tendons around some joints e.g. the patella
  • Flat bones - flat areas for muscle attachments e.g. sternum and scapula
  • Irregular bones - irregular shape with no set characteristics e.g. the vertebrae
• Types of Joints


  • Synovial - freely moveable in at least one direction e.g. shoulder or hip
  • Cartilaginous - slightly moveable joined by cartilage and allow small movements e.g. vertebrae
  • Fibrous - immovable joints that offer no movement e.g. skull
• Joint Movements


  • Flexion/Extension - Think bicep curl 'flexing'
  • Adduction/Abduction - Adduction adding to the body, Star Jumps
  • Circumduction - The circular movement of a limb, Think drawing circle with whole arm
  • Pronation/Supination - Rotation of hand, Pronated (palm down), Supinated(palm up)
  • Dorsiflexion/Plantarflexion - 'Plant' foot into ground (foot down), Dorsi (foot up)
• Functions of Muscular System

  • Bodily movement - The central nervous system tells muscles to contract/relax causing movement
  • Adequate posture - Muscles are constantly working to maintain correct posture both when awake and asleep
  • Essential bodily functions - Involuntary muscles keep functioning and cause the body to function e.g. the heart and lungs
• Muscle Types


  • Smooth Muscles - fatigue slowly compared to skeletal muscles and are found in hollow organs such as the digestive tract
  • Cardiac Muscles - Type of muscle found only in the heart and involuntary contract to maintain heart beating. Fatigues extremely slowly
  • Skeletal Muscles - Muscles connected to the skeleton and allow for movement
• Muscle Attachment


  • The origin is usually located closer to the bodies midline (proximal) end. It is usally the more stationary bone
  • The insertion is located at the distal end and is usually the more mobile bone
• Motor Units


  • A motor neuron and the fibres it stimulates are called a motor unit
  • A motor neuron may cause precise movement with 1 or 2 muscle fibres or stimulate thousands for large gross movements
• All or Nothing Principle

  When the electrical impulse reaches a certain threshold, all the fibres of that motor unit will contract simultaneously as forcefully as possible. Until the threshold is reached, no fibres will contract
• Muscle Action


  • Agonist - muscle responsible for major movement
  • Antagonist - located opposite to the agonist and will relax as the agonist contracts. This term is called reciprocal inhibition
  • Synergist - Assistant to agonist
  • Stabiliser - Stabilises the joint while agonist and antagonist do their job
• Muscle Fibre Types


  • Type I: Slow Twitch - Contain large amounts of myoglobin, mitochondria and blood capillaries, Their fibres are red and can break down ATP slowly and for an extended period of time, Best suited for endurance events
  • Type IIA: Fast Twitch Oxidative - Similar to Type I but can break down ATP much faster, Best suited for middle distance events using power and speed
  • Type IIB: Fast Twitch Glycolytic - Low amounts of myoglobin, mitochondria, and blood capillaries, Large amounts of glycogen and can break down ATP rapidly without oxygen, Fatigue very quickly, Best suited for high intensity, short duration activity.
• Muscular Contractions

  • Isoinertial action - Maintain a constant mass, Put through a specific movement, The direction of motion can change but the force on the extremity doesn't
  • Isometric - Muscle contraction against a force, Tension is produced but there is no joint movement
  • Isokinetic - Resistance adapts to maintain a constant speed throughout the movement
  • Isotonic - Muscle length changes throughout a range of motion, Muscle shortens under tension (concentric), Muscle lengthens under tension (essentric)