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Homeostasis

need for homeostasis - constancy of internal environment 

  • controlled through negative feedback loop
  • sensors - measure conditions of internal environment
  • integrating center - contains set point (proper conditions)
  • change occurs >> effectors told to increase/decrease activity
    • effectors - muscles/glands
  • body temperature - set around 37 C
    • hypothalamus detects temperature changes
    • high temperature >> sweating, dilation of blood vessels
    • low temperature >> shivering, constriction of blood vessels
    • ectothermic (cold-blooded) animals use behavior, environment to control internal conditions
  • glucose levels - controlled by islets of Langerhans
    • insulin secreted >> stimulates reuptake of blood glucose in tissues
  • antagonistic effectors - push-pull relationship
    • sets of effectors used to better control homeostasis
  • positive feedback loops - drives condition further from set point
    • don’t help maintain homeostasis
    • used in blood clotting, uterus contractions

osmolality - total moles of solute per kilogram of water 

  • osmotic pressure - measures tendency of a solution to take in water (force placed on semi-permeable membrane)
  • isotonic >> no net mov’t of water
  • osmoconformers - animals w/ same osmolality in body fluids as surrounding seawater
  • osmoregulators - animals w/ different osmolality from environment
    • must maintain constant blood osmolality
    • freshwater vertebrates = hypertonic to surrounds, tend to gain water
    • terrestrial vertebrates have more water than environment, tend to lose water
  • urinary systems evolved to help retain water

osmoregulatory organs - water sometimes removed along w/ metabolic waste 

  • protonephridia - tubules in flatworms, leads to pores on outside
    • doesn’t lead to outside/inside
  • nephridia - tubules leading to outside/inside of earthworm
  • Malphigian tubules - excretory organs in insects
  • reabsorption - transport out of tubule, into surrounding body fluids
  • vertebrate kidneys filter through pressure
  • urea - form in which nitrogenous waste is removed in mammals
    • water soluble
    • uric acid (not as water soluble) >> can precipitate out, forms gout in humans, guano in
Subject: 
Biology
Subject X2: 
Biology

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