F214:02:07 Osmoregulation Flashcards Preview

F214:02 Excretion > F214:02:07 Osmoregulation > Flashcards

Flashcards in F214:02:07 Osmoregulation Deck (51):
1

What does ADH stand for?

Antidiuretic hormone

2

What is ADH?

A hormone that increases the reabsorption of water in the collecting duct in the kidneys

3

Where is ADH released from/

The pituitary glands

4

What are osmoreceptors?

receptor cells that monitor the water potential of the blood

5

What happens in the blood has a low water potential ?

Water is moved out of the osmoreceptor cells, causing them to shrink, which alerts the neurosecretory cells

6

What is the hypothalamus?

The part of the brain which contains neurosecretory cells and various receptors which monitor the blood

7

What are neurosecretory cells?

specialised cells that act like nerve cells but release a hormone into the blood
ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb.
If an action potential passes down th axon, then the ADH is released from the terminal bulb

8

Where is ADH stored?

In the terminal bulb of the neurosecretory axon

9

What do neurosecretory cells act like?

nerve cells

10

How are neurosecretory cells stimulated?

By an action potential passing down their axon.

11

What is the posterior pituitary gland?

the hind part of the pituitary gland, which releases ADH

12

Where are ADH receptors found?

In the membranes of cells that make up the walls of the collecting duct
NOT THE CELL WALLS

13

What is osmoregulation?

The control of water and salt levels in the body

14

Why must the water balance between cells and surrounding tissue fluid?

To prevent problems with osmosis

15

Name 3 sources of water

food
drink
metabolism (eg respiration)

16

Name 4 examples of how water is lost

urine
sweat
water vapour in exhaled air
faeces

17

How much urine would be produced if you drank alot of water on a cool day ?

a large volume of DILUTE urine

18

What helps to maintain the correct balance of water being lost in the collecting duct?

The fact that the walls of the collecting duct can be made more or less permeable depending on the needs of the body

19

What do the walls of the collecting duct respond to?

the level of ADH in the blood

20

How do the walls of the collecting duct detect levels of ADH in the blood?

Cells in the wall have membrane bound receptors for ADH

21

How does ADH cause a response?

it binds with receptors in the membrane and causes a chain ofenzyme-controlled reactions inside the cell
Which leads to vesicles containing water permeable channels to be inserted into the membrane

22

What happens once ADH has binded with receptors in the membrane and caused a chain of enzyme controlled reactions inside the cell?

vesicles containing water permeable channels are inserted into membrane

23

What effect does ADH have on the cell membrane?

causes it to become more fluid

24

What effect does ADH have on the amount of urine being produced?

The more ADH there is, the more water is reabsorbed into the blood, so less urine is produced, which had a lower water potential

25

What happoens if there is less ADH in the blood than normal?

cell surface membranes fold inwards to create new vesicles to remove water-permeable channels from the membrane
so the walls become less permeable and less water passes out

26

What is the water potential of the blood monitored by?

osmoreceptors

27

What do osmoreceptors respond to?

the EFFECTS of osmosis, ie they lose water by osmosis which causes them to shrink and stimulate the neurosecretory cells in the hypothalamus.

28

Where is ADH produced spefically in the in the neurosecretory cells?

in the cell body of these cells

29

Where does the cell body of neurosecretory cells lie?

in the hypothalamus

30

Where is the terminal bulb of the neurosecretory cells found?

in the posterior pituitary gland

31

Describe the 4 stages of how ADH has an effect on dealing with a lack of water in the blood

1. ADH is detected by cell surface receptors
2. Enzyme controlled reactions
3. Vesicles containing water permeable channels fuse to membrane
4. More water can now be reabsorbed

32

What is the name for the water permeable channels found in the wall of the collecting duct?

aquaporins

33

What is the half-life of a substance?

The time taken for its concentration to drop to half its original value

34

What does ADH act upon?

The cells of the collecting duct

35

What happens once ADH has taken effect and the water potential of the blood rises?

Less ADH is released

36

What is the half life of ADH?

about 20 minutes

37

Describe the negative feedback process when there is an increase in water potential of blood?

1. detected by osmoregulators in the hypothalamus
2. Less ADH released from posterior pituitary
3. collecting duct walls become less permeable
4. less water is reabsorbed into the blood and more urine is produced
5. There is a decrease in water potential in the blood

38

Describe the negative feedback process when there is a decrease in water potential of blood?

1. detected by osmoregulators in the hypothalamus
2. more ADH is released from posterior pituitary
3. Collecting duct walls become more permeable
4. More water is reabsorbed into the blood and less urine is produced
5. There is an increase in water potential in the blood

39

What effect does alcohol have on the kidneys?

it inhibits the production of ADH and certain antibiotics such as tetracycline which can cause renal failure through a variety of mechanisms

40

Give an example of an antibiotic that alcohol affects

tetracycline

41

How can alcohol cause renal failure?

Through a variety of mechanisms eg direct toxicity to the nephron tubules

42

Give an example of useful drugs that affect the work of the kindneys

diuretic drugs

43

What effect do diuretic drugs have on the body?

they increase urine production

44

What effect do antidiuretic drugs have on the body?

They decrease urine production by increasing the reabsorption of water at the distal tube and collecting ducts without significantly modifying the rate of glomerular filtration

45

How do neurosecretory cells differ from normal nerve cells?

Neurosecretory cells manufacture a hormone in their cell body; which is transferred down the axon.
When it is released it goes straight to the blood rather than to another nerve cell

46

Explain what is meant by negative feedback

negative feedback occurs when there is a change of internal conitions which stimulates a reversal of that change so that the conditions are kept constant

47

Why is it important that ADH is broken down?

So that it is not continually acting on the walls of the collecting duct

48

Explain why drinking too much can cause a hangover

Alcohol inhibits the action of ADH so the collecting ducts are very permeable to water, so dehydration occurs as the water is lost in the urine.
and the ethanal produced from the metabolism of ethanol also contributes to a headache.

49

Suggest what symptoms may be relieved by the use of diuretic drugs

Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure.

50

Suggest what symptoms may be relieved by the use of antidiuretic drugs

Can be used to relieve diabetes insipidus and bed wetting

51

What is diabetes insipidus?

a type of diabetes caused by a lack of ADH, resulting in large amounts of watery urine