b5 homeostasis processes

• Negative feedback - controlling high body temperature

  1. Detected by the skin and hypothalamus receptors - electrical impulses sent to thermoregulatory centre
  2. Sweat glands secrete sweat, hair erector muscles relax and vasodilation occurs
  3. Optimum levels are restored
• Negative feedback - controlling low body temperature

  1. Detected by the hypothalamus and skin receptors - electrical impulses sent to the thermoregulatory centre
  2. Sweat glands stop producing sweat, hair erector muscles contract and vasoconstriction occurs
  3. Optimum levels are restored
• Negative feedback - controlling concentrated blood (lacks water)

  1. Detected by the hypothalamus, signals sent to pituitary gland
  2. Pituitary gland releases MORE ADH which makes kidney tubules more permeable
  3. More water is reabsorbed into the blood
  4. A smaller volume of concentrated urine is produced
• Negative feedback - controlling dilute blood (too much water)

  1. Detected by hypothalamus, signals sent to pituitary gland
  2. Pituitary gland releases less ADH which makes kidney tubules less permeable
  3. Less water is reabsorbed into the blood
  4. So a larger volume of less concentrated urine is produced
• How dialysis works

  1. Unfiltered blood taken, mixed with anticoagulant to prevent clotting and pumped into dialysis machine
  2. Blood and dialysis fluid are separated by a partially permeable membrane - blood and fluid flow in opposite directions, so exchange can happen between the two (conc gradient)
  3. Membrane is permeable to ions and waste substances but not large molecules eg protein
  4. Ions and glucose won’t be removed as the machine has the same conc as in blood - only excess of these will diffuse into dialysis machine
• Negative feedback - controlling high blood glucose

  1. Receptors in blood detect a high blood glucose levels and send impulses to the pancreas, stimulating insulin release
  2. Insulin travels to the liver and muscle cells, insulin causes them to take glucose in and glucose is converted into glycogen
  3. Glucose is now stored as glycogen in liver and muscle cells and levels are restored
• Negative feedback - controlling low blood glucose

  1. Receptors in the blood detect low blood glucose levels and send impulses to the pancreas, stimulating glucagon release
  2. Glucagon travels to the liver and muscle cells, glucagon causes them to use their store of glucose and glycogen is converted into glucose
  3. Glucose is released into the blood from liver and muscle cells, restoring levels
• What is diabetes?

  The inability to control blood sugar levels
• Type 1 diabetes

  • Pancreas produces little to no insulin - blood glucose levels can rise to a level that can kill you
  • Most likely hereditary - present at an early age, unlikely to develop over lifetime, not linked to weight
• Treatment for type 1 diabetes

  • Insulin therapy - insulin injected several times a day to remove glucose from blood quickly after digestion
  • Limit simple carbs intake
  • Regular exercise
  • Insulin pump - small device that pumps insulin into blood stream
• Type 2 diabetes

  • Insulin resistance - pancreas produces insulin but body cells don't respond
  • Affected by weight, age and obesity
• Treatments for type 2 diabetes

  • Can't be treated with insulin injections - body wont respond
  • Diet and exercise - removes glucose from blood
• What are primary sexual characteristics?

  Sexual characteristics that are present at birth - penis and testes, vagina and ovaries
• What are secondary sexual characteristics?


  Physical traits that develop during puberty that distinguish males from females - facial hair, breast
• Testosterone

  • Produced by the testes in males during puberty, causes changes
  • Growth of larynx
  • Darker skin
  • Muscle growth
  • Deeper voice
• Oestrogen

  • Produced by ovaries by females during puberty, causes changes
  • Growth spurt
  • Breasts develop
  • Fat deposited on thighs, hips and buttocks
  • Uterus grows
  • Menstruation
  • Causes lining of the uterus to grow
  • Stimulates LH release and inhibits FSH release
• FSH - Follicle Stimulating Hormone

  • Produced in pituitary gland
  • Causes an egg to mature in a follicle
  • Stimulates the ovaries to produce oestrogen