Ch12 Homeostasis in action

Question 1

Core body temperature

Answer 1

27°C

Question 2

What detects core body temp

Answer 2

thermoregulatory centre in hypothalamus
- contains receptors sensitive to temperature change in the brain blood flow

temperature receptors in skin

Question 3

What happens when core body temp is too cold

Answer 3

Vasoconstriction

• blood vessels that supply skin carpillaries constrict to reduce blood flow
• reduces energy transfer by radiation through the skin

skeletal muscles contract and relax rapidly(shivers)
- this needs lot of respiration
exothermic reaction raises body temp

sweat production is stopped

Question 4

What happens when core body temp is too hot

Answer 4

vasodilation

• blood vessels that supply skin carpillaries dilate, increasing blood flow
• skin flushes, transferring energy by radiation from skin to surroundings

produce more sweat
- water evaporates, transferring energy to the surroundings

Question 5

Removing waste products

Answer 5

CO2 and water is removed by the lungs during exhalation

Excess water, ions and urea are removed via the kidneys in the urine.

Water, ions and urea are lost from the skin in sweat.

Question 6

ADH

Answer 6

maintains water levels in the blood

controls permeability of collecting ducts in the kidney

Question 7

What happens if blood becomes too dilute

Answer 7

brain receptor cells detect low conc of solutes in the blood plasma
pituitary gland releases less ADH into the blood
kidney tubules permeability decreases
less water is reabsorbed into the blood from the kidneys
large volume of dilute urine is made
blood conc returns to normal

Question 8

What happens if blood becomes too concentrated

Answer 8

brain receptor cells detect high conc of solutes in the blood plasma
pituitary gland releases more ADH into the blood
kidney tubules permeability increases
more water is reabsorbed into the blood from the kidneys
small volume of concentrated urine is made
blood conc returns to normal

Question 9

Kidney function

Answer 9

1. produce urine by filtration of the blood
2. selective
   reabsorption of useful substances(glucose, ions and water)
3. doesn’t filter cells and proteins

Question 10

Liver

Answer 10

removes amino group from from excess amino acids by deamination 
forms ammonia(toxic)
ammonia is immediately converted into urea

Question 11

Urea

Answer 11

nitrogenous waste
poisonous
if levels build up it will cause damage to cells
produces by breakdown of excess amino acids in the liver

Question 12

Dialysis

Answer 12

1. person’s blood leaves body and flows between partially permeable membrane in machine
2. dialysis fluid contains no urea so it diffuses out of the blood because of steep conc gradient and into dialysis fluid
3. dialysis fluid contains the same concentration of glucose and mineral ions as healthy blood so no useful substances leave
4. acts as artificial kidney

Question 13

Kidney Transplant disadvantages

Answer 13

1. risk of rejection
2. not readily available
3. doesn’t last forever
4. have to take immunosuppressant drugs(body stops dealing effectively with infections)

Question 14

Dialysis disadvantages

Answer 14

1. Regular, really long sessions
2. follow controlled diet
3. chance of infection(constant needle in the arm
4. eventually causes serious damage