Homeostasis and Excretion.txt

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Homeostasis and Excretion.txt
2013-04-28 08:51:22
biology homeostasis excretion

Homeostasis and Excretion
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  1. What is homeostasis
    Homeostasis is the maintenance of a constant internal environment within the body
  2. How internal conditions are controlled
    Temperature - increased by shivering, lost by sweating

    Water content - increased by drinking, lost by sweating and urine

    Blood glucose - increased and decreased by hormones
  3. Necessity for homeostasis
    Homeostasis is necessary if an organism is to be independent of its surroundings and if its metabolism is to function efficiently
  4. What happens when temperature rises
    Hairs flatten, sweat evaporates, erector muscle relaxes, blood capillaries dilate
  5. How is heat and cold sensed
    Nerves in skin, blood flowing in brain
  6. Stimulus for heat
    Exercise, absorbing heat
  7. Behavioural response to heat
    • Move into shade
    • Wear less clothing
    • Drink cool water
  8. What happens when too cold
    • Hairs are upright
    • Erector muscle contracts
    • Blood capillaries contract
  9. Stimulus to cold
    Heat loss from body to surroundings
  10. Behavioural response to cold
    Exercise, shivering to increase respiration, seek heat source
  11. Skins role in homeostasis
    Regulates temperature, excretory organ sweat (urea water salt)
  12. Organs involved in homeostasis
    Lungs, control levels of co2, oxygen, water vapour

    Kidneys, control urea, water and salt levels

    Pancreas and liver, control blood sugar levels
  13. What is excretion
    Excretion is the removal of waste products of metabolism from the body
  14. Excretory organs and what they excrete
    • Kidneys - urea, water and salt
    • Lungs - co2 and water vapour
    • Skin - sweat (urea water and salt)
  15. F: aorta
    Brings oxygenated blood to pelvic trgion
  16. F: renal artery
    Blood supply to the kidney
  17. F: kidney
    Filters the blood, reabsorbs any useful substances
  18. F: ureter
    Transfers urine from kidney to bladder
  19. F: bladder
    Stores urine
  20. F: sphincter muscle
    Controls opening and closing of bladder (release of urine)
  21. F: urethra
    Passes urine out of the body
  22. R: renal vein
    Passes any reabsorbs substances from kidneys back to bloodstream
  23. R: Vena cava
    Returns deoxygenated blood to the heart
  24. Urea production
    • Urea is produced in the liver
    • Amino acids are broken down to make urea
    • Process is called deamination
  25. Where in kidney is filtration
    Outer cortex

    Small molecules glucose, amino acids, water, salts, urea filter out
  26. Kidney reabsorption
    Blood vessels reabsorb back useful nutrients from tubes

    Urea excess salts and water continue down onto bladder
  27. What are too large to be filtered
    Red blood cells, white blood cells, lipids and proteins
  28. Filtration in nephron
    Renal artery divided into GLOMERULUS at top

    Bowmans capsule surrounds each. Smaller molecules are forced under pressure out of plasma into lumen of capsule, forming GLOMERULAR FILTRATE

    All but large proteins and blood cells are filtered
  29. Reabsorption in nephron
    Proximal convoluted tubule, glucose, amino acids, salts and water back into blood

    Food molecules by active transport

    Water by osmosis from loop of henle

    Urea, salt and water pass as urine into bladder
  30. What is osmoregulation
    Kidney regulates amount of water in body by regulating amount of urine produced
  31. What is ADH
    Anti-diuretic hormone

    Controls whether distal tubule and collecting ducts reabsorb water or not
  32. When body is low on water
    ADH is secreted from pituitary gland

    More water reabsorbed only small volume of urine is produced
  33. When body is high on water
    Turns of ADH production

    Large volume of urine