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2014-04-14 06:07:38
Biology Hormones camturnbull

AQA BIOL5 Hormones
Show Answers:

  1. From where are hormones released?
    Endocrine glands
  2. How are hormones transmitted
    They are carried in the bloodstream
  3. What functions do hormones serve?
    They change the physiological activities of a target organ by binding to specific receptors in the membrane of its cells
  4. Give four characteristics of the endocrine system
    • Slow transmission
    • Widespread effect
    • Long lasting response 
    • Effects are sometimes irreversible or permanent
  5. Give 4 characteristics of the nervous system
    • Fast transmission
    • Localised effect
    • Short lived response 
    • Reversible and temporary effects
  6. What are chemical mediators?
    Chemicals released by some mammalian cells that only affect cells in the immediate area
  7. How are chemical mediators different from hormones?
    • They are not distributed around the body in the bloodstream 
    • They are not secreted from glands
  8. What is histamine
    • A chemical mediator released by white blood cells following injury or response to an allergen
    • Causes dilation of arterioles and increases permeability of capillaries
  9. What are prostoglandins?
    • Mediators released from most cells following injury
    • Causes increased permeability of capillaries, blood clotting and blood pressure regulation
  10. What are plant growth factors?
    Chemicals, such as IAA, that result in a change in growth causing a tropism
  11. How do growth factors respond to stimuli?
    • They are transported to one side of the stem or root 
    • This causes the side to grow more or less than the other 
    • The effect of this unequal growth is bending of the root or stem towards or away from the stimulus
  12. Give an example of a tropism caused by growth factors
    • IAA is transported to the shaded side of them stem
    • This causes more growth to occur on that side
    • The increased growth makes the stem bend towards the light
  13. How are growth factors affected by gravity?
    • They are transported to the lower side of the root 
    • This causes growth inhibition on that side 
    • This results in the downward bending of the root with the force of gravity