Movement in humans

• Movement


  Brought by musculo-skeletal system: bones, muscles, joints, tendons, ligaments
• Skeleton structure


  • Vertebrates have an endoskeleton
  • Human skeleton is made up of bones and cartilages
• Bones


  • Living tissue composing of calcium salts (calcium phosphate), living cells, proteins and water
  • Has blood vessels, arteries supply nutrients to bones
• Soups cooked with trotters are not a good source of calcium salts as calcium salts are not readily dissolved in water
• Calcium salts can dissolve in vinegar as minerals can dissolve
• Compact bone


  Dense and hard, forms outer shell of all bones and shafts of limb bones, provides great strength for supporting the body's weight
• Spongy bone


  Porous, makes up much of the heads of limb bones, provides strength with minimum additional weight
• Osteoporosis


  Bone disease caused by more bone cells being reabsorbed than being deposited, results in progressive loss of bone density and thinning of bone tissue, making bones more porous and easy to break
• Preventing osteoporosis


  1. Take in more calcium for bone formation

  2. Take in more vitamin D to help the absorption of calcium from food

  3. Do regular weight-bearing exercise to stimulate bone formation
• Functions of bones


  • Supporting and maintaining body shape
  • Protecting internal organs eg brain, heart, lungs, spinal cord
• When bones are soaked in HCl, they become soft and flexible because the inorganic component is dissolved away
• Structure of bones

  • Hollow space in the middle filled with fatty tissue called yellow bone marrow
  • Tiny cavities at both ends filled with red bone marrow where red and white blood cells are produced
• Cartilage


  A matrix of collagen protein, contains less minerals, more elastic and flexible than bones, found on the ends of bones
• Functions of cartilage


  • Acting as shock absorber and reducing friction between two bones when moving against each other
  • Giving shape to structures eg ears and nose
  • Supporting the wall of trachea and bronchi
• Cartilage has no blood vessels and nerves, unlike bones
• Wearing of cartilage causes serious pain as it exposes the pain receptors which are stimulated
• Framework of the human skeleton

  • Axial (central axis): skull, rib cage, vertebral column
  • Appendicular (both sides): girdles, limb bones
• Function of axial skeleton

  Mainly for support and protection of internal organs
• Function of appendicular skeleton

  Mainly for movement
• Features of skull


  • Consists of cranium and facial bones
  • Cranium bones fused together at sutures (immovable joint)
  • Protects brain and sense organs eg eyes and ears
  • Upper jaw and cranium → immovable joint
  • Lower jaw and cranium → movable
• Features and functions of vertebral column

  • Supports the weight of upper body
  • S-shape acts as a spring to absorb shock during movement
  • Protects spinal cord
  • Provides surfaces for muscle attachment to maintain body upright
  • With compressible intervertebral discs allows bending and acts as shock absorber
• Structural features of backbone that allow it to bend

  • The backbone is made up of many vertebrae / small bones which are articulated by joints
  • There are compressible cartilage discs between the vertebrae
• How vertebrae help maintain upright position

  Vertebrae are linked together by ligaments to form a column

  and they allow the attachment of muscles which contract to produce required force to keep skeleton in position and maintain posture
• Features and functions of rib cage

  • Held by sternum in front and vertebral column at the back
  • Protects lungs and heart
  • Helps bring about breathing actions
• Function of limb bones

  Allow movement of the body
• Features and functions of girdles

  • Flat bones
  • Pectorial girdles (shoulders) attach arms to axial skeleton
  • Pelvic girdle (hip) attaches legs to axial skeleton
• Functions of the skeleton

  • Support body weight and give shape
  • Allow movement (skeleton: surfaces for muscle attachment; bones and muscles together)
  • Protect organs
  • Produce blood cells
  • Store minerals and lipids
• Joint


  Junction where two or more bones meet
• Types of joints


  • Immovable (eg joint between skull bones)
  • Movable (hinge joints and ball-and-socket joint)
• Movable joints

  • Consist of synovial cavity, ligament, synovial membrane, synovial fluid, membrane
• Ligament


  Tough elastic fibres forming capsule at joint, hold bones together and limit degree of movement to prevent dislocation
• Synovial membrane


  On inner surface of capsule, secretes synovial fluid into synovial cavity
• Synovial fluid


  Acts as a lubricant to reduce friction between bone surfaces during movement, nourishes cartilage cells
• Cartilage


  Acts as shock absorber to reduce friction between bones and protect them from wearing away
• Osteoarthritis


  Top layer of cartilage breaks down and wears away, causing bones to rub together leading to pain, swelling, loss of motion, and the joint may lose normal shape over time with bone spurs growing at the edges
• Types of movable joints

  • Hinge joint (eg elbow, knee, fingers, toes)
  • Ball-and-socket joint (eg shoulder, hip)
• Function of hinge joints


  Allow movement of bones in one plane only
• Function of ball-and-socket joints

  Allow rotational movement of bones in (almost?) all directions, with the ball-shaped head of one bone fitting into the cup-shaped socket of the other bone
• Skeletal muscles


  Muscle consists of muscle fibres which are elongated in shape and able to contract, with light and dark bands (striated), under conscious control (voluntary muscles)
• Transmission of nerve impulses across neuromuscular synapse / junction

  1. Nerve impulses arrive at the end of motor neurone

  2. Nerve endings stimulate release of neurotransmitter from synaptic vesicles

  3. Neurotransmitters diffuse across synaptic cleft to muscle fibres

  4. Neurotransmitters bind to receptors on muscle fibre membrane and stimulate it to generate nerve impulses

  5. Nerve impulses spread along muscle fibres and trigger muscle contraction