Osmoregulation

Question 1

Where are the 3 places that water is gained from and the 4 places it is lost from?

Answer 1

From: food drink, metabolism. Lost from: urine, sweat, water vapour in exhaled air, faeces

Question 2

What part of the kidney can be altered depending on the needs of the body in terms of water?

Answer 2

walls of collecting duct can be made more/less permeable

Question 3

What do the walls of the collecting duct respond to?

Answer 3

level of antidiuretic hormone (ADH) in the blood, cells in the wall have membrane-bound receptors for ADH, ADH binds and causes chain of enzyme controlled reactions inside cells

Question 4

What is the end result of ADH binding with collecting duct cells?

Answer 4

insert vesicles containing water permeable channels into the membrane: aquaporins, makes walls more permeable to water (ADH in blood = more channels)

Question 5

What happens when there is low levels of ADH in the blood?

Answer 5

cell membranes fold inwards to make new vesicles that remove water permeable channels, wall less permeable to water

Question 6

What is the water potential of the blood monitored by?

Answer 6

osmoreceptors in hypothalamus, respond to effects of osmosis, when low water potential, receptors lose water by osmosis so shrink

Question 7

What cells do osmoreceptors stimulate?

Answer 7

neurosecretory cells, specialised neurones which produce and release ADH, ADH flows down axon to the terminal bulb in the posterior pituitary gland (stored there until needed)

Question 8

What happens when neurosecretory cells are stimulated?

Answer 8

send action potentials down axons, cause release of ADH

Question 9

How does the ADH enter the blood?

Answer 9

enters blood capillaries running through posterior pituitary gland, transported around body

Question 10

What happens when the water potential of the blood rises again?

Answer 10

less ADH released, ADH slowly broken down (half life = 20 mins) so collecting ducts receive less stimulation