Homeostasis

Question 1

homeostasis

Answer 1

maintenance of a constant internal environment despite external changes

Question 2

examples of homeostasis

Answer 2

body temperature
pH
water potential

Question 3

dynamic equilibrium

Answer 3

constant changes occur but corrective mechanisms bring the internal environmental conditions back to a set point

Question 4

negative feedback process

Answer 4

receptor detects deviation from set point
sends instructions to co-ordinator
co-ordinator communicates with effector
effector makes corrective responses

Question 5

osmoregulation

Answer 5

control of body fluid water potential by negative feedback - type of homeostasis, under hormonal control

Question 6

osmoregulation process

Answer 6

osmoreceptors in hypothalamus detect decrease in blood plasma water potential
signal sent to pituitary gland
pituitary gland releases adh into blood
adh carried to kidneys and binds to aquaporins in collecting duct and dct
allows more water to be reabsorbed by osmosis
increases water potential to set point

Question 7

adh role

Answer 7

increases the permeability of the collecting duct and dct allowing more water to be reabsorbed, urine produced will be more concentrated and a lower volume

Question 8

aquaporins

Answer 8

intrinsic protein channels which transport water across the phospholipid bilayer during osmosis

Question 9

adh and aquaporins process

Answer 9

adh binds to aquaporins in bilayer
vesicles with aquaporins fuse with membrane
increases number of available aquaporins
increases permeability of membrane
allows more water to be reabsorbed
– this is reversible –