bio cba 2!

• Reflex arc


  Sensory neurone -> spinal cord -> motor neurone -> brain
• Nervous system


  • Brain is part of the central nervous system (CNS)
  • Focus on neurones involved (sensory relay and motor)
• Sensory neurone


  Transmits nerve impulses from touch receptors to relay neurone in the spinal cord
• Relay neurone


  Transmits nerve impulses from sensory neurone to motor neurone
• Motor neurone


  Transmits nerve impulses from CNS to muscle effectors
• Voluntary action


  May or may not involve sensory neurone, involves conscious control
• Reflex action


  Involves sensory neurone, does not involve conscious control
• Skin arterioles


  • Constrict to conserve heat
  • Supply blood to capillaries
• Blood capillaries


  • One cell thick, cannot constrict and dilate
• Shunt vessels


  • Work in opposite direction to skin arterioles, send more blood to blood capillaries or keep blood away from blood capillaries
• Wet bulb global temperature


  Measures amount of evaporation from a wet cloth over a thermometer to simulate high humidity
• High wet bulb global temperature


  Simulates high humidity, less evaporation
• Low wet bulb global temperature


  Simulates low humidity, more evaporation
• High wet bulb global temperature during vigorous exercise


  Person may suffer from heatstroke
• Accommodation of the eye

  1. Ciliary muscle relaxes, suspensory ligaments become taut, lens becomes less convex and thinner (for distant objects)

  2. Ciliary muscle contracts, suspensory ligaments slacken, lens becomes more convex and thicker (for near objects)
• Iris muscles

  • Radial muscles contract, circular muscles relax to dilate pupil (in dim light)
  • Circular muscles contract, radial muscles relax to constrict pupil (in bright light)
• Specialised cells

  • Red blood cell
  • Skeletal muscle cell
  • Root hair cell
• Red blood cell


  Delivers oxygen to all parts of the body, contains haemoglobin, circular biconcave shape, no nucleus, flexible
• Root hair cell


  Absorbs water and mineral salts from the soil, long narrow extension, maintains low water potential in vacuole
• Skeletal muscle cell


  Contracts and relaxes to bring about movement, contains many mitochondria, has contractile protein fibres, has many nuclei
• Villi is the plural of villus
• Increased surface area to volume ratio improves absorption