12 - Homeostasis in Action

• Thermoregulation - control of core body temperature
• Detection of body temp is in the hypothalamus. Contain receptors that senstive to temperature of blood flowing through brain
• Cooling down:

  • impulses sent from thermoregulatory centre so more energy transferred to surroundings
  • more sweat
  • transfers energy to surroundings
  • vasodilation
  • capillaries dilates so more blood flow
• Keeping warm:

  • impulses sent from thermoregulatory centre so less energy transfer to surroundings
  • goosebumps
  • sweat production stops
  • vasoconstriction
  • capillaries constrict allowing less blood flow
  • shiver
  • muscle quickly contract and relax - needs respiration
  • exothermic reaction so raise body temp
• Removing CO2:

  • CO2 produces acidic solution which affects enzymes
  • CO2 goes in blood and out of lungs
• Removing Urea:

  • produced by breakdown of excess amino acids in liver
  • poisonous and damages cell if too much
  • urea passes from liver cell to blood to kidney then out body
• Kidney is important for homeostasis of water. It removes waste and regulate levels of ions
• If short of water, kidney produces very concentrated urine so water is saved.
• If too much water, kidney produces dilute urine to remove excess water
• How kidney works?

  • Tubule filters blood
  • Kidney reabsorbs amino acids, some mineral ions and soms water back into blood.
  • selective reabsorption occurs
  • urine goes into bladder to be store then leaves body
• Less ADH released, less water reasorbed
• Dialysis - machine that carries out function of the kidney by removing waste products from the blood
• Disad of dialysis:

  • have controlled diet
  • regular long session connected to it
  • feel tired and unwell
  • expensive in long term
• Disad. of transplant:

  • risk of being rejected
  • only last 10 years