coordination and response

• Homeostasis


  The maintenance of a constant internal environment
• Homeostatic control by negative feedback


  A process that maintains a stable internal environment in the body by reversing any changes that occur from the set point
• Set point


  A desired or ideal value or a narrow range of values for a particular factor
• Negative feedback loop

  1. Change detected

  2. Corrective mechanisms activated

  3. Conditions returned to set point

  4. Corrective mechanisms switched off
• Blood glucose concentration control

  Negative feedback mechanism
• Blood glucose regulation

  1. Blood glucose level increases

  2. Pancreas releases insulin

  3. Insulin stimulates liver to remove excess glucose and convert to glycogen

  4. Blood glucose level decreases
• Blood glucose regulation

  1. Blood glucose level decreases

  2. Pancreas releases glucagon

  3. Glucagon stimulates liver to break down stored glycogen into glucose

  4. Blood glucose level increases
• Type 1 diabetes


  Condition where body is unable to control blood glucose levels due to lack of insulin production by pancreas
• Type 1 diabetes treatment

  • Injecting insulin
  • Monitoring blood glucose levels
  • Careful diet
  • Regular exercise
• Parts of the skin

  • Hairs
  • Hair erector muscles
  • Sweat glands
  • Receptors
  • Sensory neurons
  • Blood vessels
  • Fat tissue
• Skin's role in maintaining constant body temperature

  • Insulation
  • Sweating
  • Shivering
  • Vasodilation and vasoconstriction
• Maintaining constant body temperature (hot conditions)

  1. Temperature change detected by thermoreceptors

  2. Brain initiates responses

  3. Increased sweating

  4. Vasodilation

  5. Flattening of skin hairs

  6. Body cools down
• Maintaining constant body temperature (cold conditions)

  1. Temperature change detected by thermoreceptors

  2. Brain initiates responses

  3. Shivering

  4. Vasoconstriction

  5. Erection of skin hairs

  6. Body warms up
• Tropism


  Growth movement or response of a plant towards or away from a stimulus
• Gravitropism

  • Shoots are negatively gravitropic (grow upwards against gravity)
  • Roots are positively gravitropic (grow downwards towards gravity)
• Phototropism

  • Plant shoots are positively phototropic (grow towards light)
  • Plant roots are negatively phototropic (grow away from light)
• Auxin


  Hormone that controls plant growth and direction in response to stimuli
• Auxin distribution and shoot growth

  1. Auxin made in shoot tip

  2. Auxin promotes cell division and elongation

  3. Uneven auxin distribution causes uneven growth and bending towards light (positive phototropism)
• Investigating phototropism in shoots

  1. Plants placed in boxes with light from different directions

  2. Shoot bends towards light due to uneven auxin distribution
• Investigating gravitropism in shoots and roots

  1. Bean seedlings placed with roots facing down or horizontally

  2. Roots grow downwards (positive gravitropism)

  3. Shoots grow upwards (negative gravitropism)