Homeostasis

• Homeostasis


  Mechanisms to maintain a dynamic equilibrium, with small fluctuations over a narrow range of conditions.
• Give an example of positive feedback


  The release of oxytocin during labour.
• Ectotherms


  Organisms that rely on external sources of heat and behavioural activities to regulate their body temperature.
• Nmae 2 advantages/disadvantages to being ectotherm


  Use less food in respiration

  Use more energy for growth

  Less active in cooler temps

  May not be capable of activity during winter
• Endotherm


  Organisms that can control production and loss of heat to maintain their body temperature.
• Name 2 advantages/disadvantages to being endotherm.


  Constant body temp

  Active in cold temps

  Lots of energy used to regulate body temp

  more food is needed
• Excretion


  Removal of metabolic waste from the body.
• What are the two main substances removed via excretion ?

  Carbon dioxide and Urea
• What is the name of the tube connecting the kidney to the bladder ?

  ureter
• Name 3 ways CO2 is transported in the blood?


  Dissolves in plasma forming carbonic acid

  Combines with haemoglobin to form carbaminohaemoglobin

  Transported as hydrogencarbonate ions
• What is the effect of carbaminohaemoglobin ?


  Lowers Hb affinity for oxygen.
• How are hydrogencarbonate ions formed?


  Dissociation of carbonic acid
• Why must Carbon dioxide be removed from the body ?


  High levels can lower the pH (respiratory acidosis).
• Wha the effects of respiratory acidosis ?


  difficult breathing, headaches, CNS issues
• Why are amino acids excreted ?


  The body cannot store them
• What are the 2 stages of amino acid excretion ?


  Deamination

  Formation of urea
• What happens in deamination ?


  Amino acid + Oxygen = keto acid and ammonia
• How is urea formed ?


  ammonia + carbon dioxide = urea + water
• Why is ammonia toxic ?


  It can cross the blood-brain barrier and interfere with CNS
• Name 2 vessels leaving the liver ?

  The bile duct

  The Hepatic Vein
• Name 2 vessels entering the Liver ?

  Hepatic Artery

  Hepatic Portal vein
• What is the function of hepatic portal vein ?


  Brings blood rich in products of digestion (glucose/amino acids) from the intestine to the liver.
• What are Kupffer cells?


  macrophages in the liver
• What is the role of Kupffer cells?


  Destroy worn out red/white blood cells, bacteria and foreign matter in the sinusoid.

  They breakdown haemoglobin into bilirubin (brown faeces).
• What does the liver have indirect control of (3 thing ) ?


  blood glucose levels

  amino acid level

  lipid levels
• What does the liver breakdown ?


  toxins

  hormones

  red blood cells
• What is synthesised in the liver ?


  red blood cells in the foetus

  bile

  plasma proteins

  cholesterol
• What are keto acids used for ?


  Converted into lipids and cholesterol and used in kerbs cycle.
• Describe the gross structure of the liver ?

  Liver lobules are connected to branches of hepatic portal vein and hepatic artery supply the lobules and flow towards the central vein. There are sinusoids surrounding the hepatocytes leading towards the central vein.
• What connects the bile duct to the hepatocytes ?


  canaliculi
• What does the ornithine cycle show ?


  The formation of urea.
• Where does detoxification occur in the liver ?


  The smooth endoplasmic reticulum of the hepatocytes.
• Name the vessel providing blood to the kidney ?

  Renal artery
• What is the whiteish area in the centre of the kidney called ?

  pelvis
• Describe the location of the nephron ?


  Begins in the cortex and drops down into the medulla.
• Describe the structures of the nephron ?


  Bowmans capsule, proximal convoluted tubule, loop of henle, distal convoluted tubule and collecting duct.
• On a microscope how can you tell the difference between a proximal convoluted tubule and a distal convoluted tubule and why?


  Proximal has fuzzy edges from the brush border.
• Name 2 functions of the kidney ?


  Osmoregulation and excretion of nitrogenous waste
• osmoregulation


  the control of water potential of the blood
• What collects in the pelvis ?


  urine