Homeostasis

• Explain why a decrease in body temperature is an advantage to animals during hibernation? [2]

  • less energy transferred for maintaining higher body temperature
  • so body energy store lasts longer
• Why does an animal have a higher body temperature when it's active? [2]

  • movement requires energy from respiration
  • respiration releases heat which increases body temperature
• Explain how the dilation of blood vessels in skin can help decrease body temperature [3]

  • there is more blood flow near the surface of skin
  • so more heat is lost from the blood
  • which cools blood which cools body
• Why would someone who sweats profusely be advised to take salt tablets? [1]

  To replace ions/ salt lost in sweat
• Control variables in response of shoot to light experiment

  • same volume of water
  • same temperature|
  • same species of plant
  • same age of shoot
  • same amount of minerals/ions
• Why is glucose found in the blood but not in the urine? [3]

  • glucose enters blood from small intestines
  • glucose is filtered out of the blood
  • glucose is a small molecule
  • glucose is reabsorbed into the blood stream
  • by active transport
• Why would someone with kidney disease have protein in their urine and a healthy person not? [2]

  • In a healthy person, protein is not present because proteins are large molecules/ cannot pass through filter
  • In a person with kidney disease, the protein passes through into the urine
• Advantages of having a kidney transplant rather than dialysis

  • no build-up of toxins/ keeps blood concentration constant
  • prevents high blood pressure
  • don't need restricted diet/ restricted fluid intake
  • blood clots may result from dialysis
  • infection may result from dialysis
  • with dialysis, blood may not clot properly due to anti-clotting drugs
• Disadvantages of a kidney transplant, compared to dialysis

  • rejection/problem finding tissue match
  • use of immuno-suppressant drugs may lead to difficulty with other infections
  • risks associated with surgery (eg infection)
• Why is protein not found in urine of a healthy person? [2]

  • protein molecules too large
  • cannot pass through filter into kidney tubule
• Explain how dialysis treatment restores the concentrations of dissolved substances in the blood to normal levels [4]

  • use of partially permeable membrane/only small molecules can pass through membrane
  • dialysis fluid has 'ideal' concentrations of solutes
  • diffusion of waste substances out of blood (eg urea)
  • maintains equilibrium between plasma and dialysis fluid
• Two hormones that stimulate the ovaries

  LH and FSH
• Explain how the hormones insulin and glucagon control the person’s blood glucose concentration after the meal [5]

  • blood glucose increases after meal detected by pancreas causes insulin secretion
  • insulin causes glucose to enter cells
  • insulin causes glucose conversion into glycogen
  • so blood glucose decreases causing glucagon secretion
  • glucagon causes glycogen to be converted to glucose
• Why does a person with Type 2 diabetes often has a higher blood insulin concentration than a non-diabetic person? [3]

  • cells absorb less glucose
  • so glucose concentration in blood remains high
  • high blood glucose causes pancreas to release more insulin
• Explain why urine contains mineral ions and urea, but no glucose or protein [4]

  • proteins are not filtered
  • glucose is filtered and reabsorbed
  • ions are filtered and some are reabsorbed
  • urea is filtered
• Explain why a man’s urine contains a higher concentration of mineral ions and urea on a hot day than on a cold day [4]

  • more sweating occurred
  • more water loss by sweating
  • more water reabsorption by the kidney
  • lower volume of urine
• Describe how the water content of the blood is controlled [6]

  • if water content too low, ADH released
  • from pituitary gland
  • into the blood
  • causing kidney to reabsorb more water
  • more concentrated/small volume urine produced
  • if water content too high, ADH lowered
  • less water reabsorbed by kidney
  • more dilute/larger volume urine produced
• Describe how the body responds when a decrease in core body temperature is detected [6]

  • Detected by receptors in blood flowing past brain/in skin
  • signal sent to thermoregulatory centre in hypothalamus
  • less sweat to reduce heat lost by water loss
  • hairs stand up which trap heat
  • vasoconstriction of blood vessels supplying skin
  • causing less blood flow to the skin
  • so less energy/ heat is lost to the surroundings
  • shivering by muscle contraction releases energy due to more respiration
• Describe how a healthy kidney produces urine [5]

  • the kidney filters the blood
  • then reabsorbs all of the glucose
  • reabsorbs some of the ions
  • reabsorbs some of the water
  • releases urea in urine
• Explain why a transplanted kidney may be rejected [3]

  • immune system
  • produces antibodies
  • which attack the antigens on the transplanted kidney
• How can doctors prevent kidney rejection

  • tissue typing to find match
  • treating with immunosuppressants
• Role of the pituitary gland

  secretes hormones into the blood to either have an effect on the body or act on other glands to stimulate them to produce different hormones
• Role of pancreas

  • secretes insulin
  • controls blood glucose levels
• Role of thyroid

  • secretes thyroxine
  • controls metabolic rate, heart rate and temperature
• Role of adrenal gland

  • secretes adrenaline
  • involved in 'fight or flight' response
• Roles of ovary

  • secretes oestrogen
  • involved in menstrual cycle and development of female secondary sexual characteristics
• Role of testes

  • secretes testosterone
  • is involved in the production of sperm and the development of male secondary sexual characteristics
• How does the body increase blood glucose level? [3]

  • pancreas produces hormone glucagon
  • glucagon binds to liver cells causing glycogen to be broken down into glucose
  • glucose released into blood, increasing blood glucose concentration
• How is type 1 diabetes treated

  • insulin injections at meal times
  • advised to limit intake of simple carbohydrates which contain lots of glucose
• How is type 2 diabetes treated?

  • reducing number of simple carbohydrates in diet
  • losing weight
  • increasing excercise
• Role of kidneys

  • filtering out waste products
  • selectively reabsorbing useful substances such as glucose, ions, and water
• How is urea formed?

  • amino acids are the products of digestion of proteins
  • amino acids are deaminated in liver to form ammonia
  • ammonia is toxic and converted to urea
• How does the kidney decrease water loss?

  • ADH is released into pancreas by pituitary gland
  • travels in bloodstream to kidney tubules
  • an increased amount of ADH in tubules increased the water concentration, increasing the permeability to water, so more water moves out of the tubule and back into bloodstream
  • so less volume of more concentrated urine
• Disadvantages of dialysis

  • Increased chance of blood clots forming
  • takes a lot of time
  • have to follow strict diet
  • build up of waste products between sessions may result in feeling ill
• Role of FSH

  • stimulates growth of follicles in which egg matures
  • stimulates the ovaries to produce oestrogen
• Role of oestrogen

  • causes thickening of uterus lining
  • secreted as a result of FSH
  • stimulates production of LH and inhibits the secretion of more FSH
• Role of LH

  • produced as a result of oestrogen
  • triggers ovulation
• Role of progesterone

  • maintains lining of the uterus
  • supports pregnancy if egg is fertilised
  • inhibits release of FSH an LH
• How does the contraceptive pill work?

  • contains oestrogen and progesterone
  • oestrogen levels are constantly high, inhibiting FSH so no eggs mature
  • lining also stops developing and mucus in cervix becomes thick so sperm cannot move through
• Side effects of contraceptive pill

  • changes in mood
  • depressions
  • breast pain/tenderness
  • breast enlargement
  • increased blood pressure