B2.044 Polyuria/Polydipsia Flashcards Preview

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Flashcards in B2.044 Polyuria/Polydipsia Deck (41)
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1

what is normal daily urine output?

1-1.5 L/day

2

what is polyuria?

increased urine output
>3L/day

3

what is polydipsia?

excessive thirst and water ingestion

4

what 2 mechanisms account for water intake?

ingestion- 2000 ml/day
metabolism- 400 ml/day

5

what 4 mechanisms account for water loss?

skin- 400 ml/day
lungs- 400 ml/day
intestine- 100 ml/day
kidney- 1500 ml/day

6

what percentage of your body is water content?

60-65%

7

how is water content in the body distributed in tissues?

50% intracellular fluid
10% interstitial fluid
5% intravascular fluid

8

what is the blood pressure at the arterial and venous ends of the blood vessels?

arterial - 30 mmHg out of capillary
venous- 10 mmHg into the capillary

9

what is oncotic pressure?

pressure due to proteins in the body fluids

10

what is the net oncotic pressure difference?

20 mmHg into the capillary, constant along vessel

11

where is there a pressure difference favoring water efflux from vessel?

arterial end

12

where is there a pressure difference favoring water entrance to vessel?

venous end

13

what are the homeostatic functions of the kidney?

regulation of extracellular fluid volume
regulation of extracellular fluid electrolyte composition
regulation of extracellular fluid acid base balance

14

what are the excretory functions of the kidney?

metabolic waste products
foreign substances and toxins

15

describe the role of different nephron sections in water reabsorption/excretion

1. blood is filtered in the glomerulus
2. water is reabsorbed in the proximal tubule in a constitutive fashion
-60-70% of water
-linked to Na+
3. loop of henle not directly involved in reabsorption, but is fundamental in ADH dependent water balance
4. distal tubule/collecting duct water reabsorption is regulated by ADH

16

what two components are maintained in regulation of water balance?

ECF volume
ECF osmolarity

17

when does the posterior pituitary release ADH?

increased ECF osmolarity
stimulation of thirst center and osmoreceptors

18

what is the effect of ADH on urine and plasma H2O?

decreases urine volume and increases urine osmolarity to save water in the plasma
once there is enough plasma H2O, there is negative feedback which inhibits ADH

19

a decrease in these metrics causes an increase in ADH

volume and pressure

20

an increase in this metric causes and increase in ADH

plasma osmolarity

21

what is the relative osmolarity and flow rate of urine during diuresis?

high flow
low osmolarity

22

what is the relative osmolarity and flow rate of urine during antidiuresis?

low flow
high osmolarity

23

what are the 2 factors required for water reabsorption in the kidney?

1. permeability across the renal tubule membrane
2. a gradient for water movement across the tubule

24

how does ADH affect the distal tubule?

tubule impermeable
ADH increases permeability by creating channels for water to exit

25

what is the difference between the dlh and the alh?

dlh is permeable, alh is not
this allows for the creation of a more dilute fluid in the alh

26

describe the countercurrent mechanism

in the dlh, water exits and salt enters
in the alh, salt exits and water is maintained due to impermeability, creating a dilute solution
in the distal tubule and collecting tubule, there is now a gradient between the dilute filtrate and salty environment of the medullary interstitium so that water may flow out of the tubule if ADH is present and makes it permeable

27

what is the response of the kidneys and the resulting effect on urine of an event resulting in loss of water > solutes?

water reabsorption in kidney
decrease urine volume
increase urine conc. (hypertonic)

28

what is the response of the kidneys and the resulting effect on urine of an event resulting in excess water over solutes?

water excretion
increase urine volume
decrease urine conc. (hypotonic)

29

what is the response of the kidneys and the resulting effect on urine of an event resulting in excess of isotonic fluid?

water and solute excretion
increase urine volume

30

what are two mechanisms that lead to polyuria?

1. low solute reabsorption
2. abnormal ADH levels