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BIOM20002 - HSF > Lecture 65 - Urine Concentration > Flashcards

Lecture 65 - Urine Concentration Flashcards

0
Q

What is the purpose of the LOH?

A

To set up a high osmotic force in the medulla

By secreting stuff into the medulla

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1
Q

Why can ACE inhibitor drugs be dangerous

A

Can lead to renal failure

If a person has an underlying problem with glomerular function, giving an ACE inhibitor can lead to a big decrease in GFR

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2
Q

What determines how much water leaves the collecting duct to be reabsorbed?

A

Vasopressin

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3
Q

What are the fluid inputs into the body?

A

Food & Drink

Metabolism

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4
Q

What is average water input daily?

A

2.5 litres

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5
Q

What are the fluid outputs?

A

Urine
Lungs
Skin
Faeces

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6
Q

What is average fluid output per day?

A

2.5 litres

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7
Q

What is a negative water balance in the body most obvious as?

A

Increased ECF osmolarity

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8
Q

Which cells detect changes in osmolarity?

Where are these cells?

A

Osmoreceptor cells in the anterior hypothalamus

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9
Q

Describe the function of the osmoreceptor cells

A
  1. Increased osmolarity of ECF
  2. Fluid leaves osmoreceptor cells
  3. Cells shrivel
  4. Release of ADH from posterior pituitary
  5. Increased fluid reabsorption
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10
Q

What is the osmolarity of the body?

A

300 mmol

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11
Q

What is the concentration of vasopressin at the set point?

A

Certain level, not zero

This allows us to go higher as well as lower

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12
Q

What is the relationship between vasopressin and osmolarity?

A

Directly proportional

The higher the body’s osmolarity, the greater the release of vasopressin

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13
Q

What is the difference between diabetes mellitus and diabetes insipidus?

A

Mellitus: urine is sweet

Insipidus: urine isn’t sweet

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14
Q

What is the relationship of ECF volume and vasopressin release?

A

Inversely proportional

However, ECF volume has to be very low for vasopressin levels to increase very much

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15
Q

Where are aquaporins found on the loop of Henle?

Where aren’t they?

A

Thick ascending: never any aquaporins

16
Q

What is the range of urine osmolarity?

A

3-1200 mOsm

17
Q

How much solute must be excreted per day?

A

600 mOsm

18
Q

How much water must be excreted per day?

When does this change?

A

500 mL

Less than 500 ml indicates kidney failure

19
Q

Describe the relative concentration of water leaving the loop of Henle

A

Dilute

100 mOsm

20
Q

Describe the relative concentration of fluid leaving the PCT

A

Isosmotic

300 mOsm

21
Q

Describe the relative concentration of urine at the deepest point on the loop of Henle

A

Concentrated

1200 mOsm

22
Q

What is being reabsorbed from the descending loop of Henle?

A

Lots of water

Because the medulla is so concentrated

23
Q

What is being reabsorbed from the thick ascending loop of Henle?

Where does this go, and what is the result of this?

A

Solute is being reabsorbed

Goes into the medulla, making it very hyperosmolar

24
Q

The fluid leaving the ascending loop of Henle is very hyposmolar. How do we make concentrated urine?

A

Open up the aquaporins in the DCT and the collecting duct

25
Q

What is the concentration of the medulla due to?

A

Sodium

Urea

26
Q

Why is some urea reabsorbed?

A

Stays in the medulla, creating the high concentration

27
Q

Describe absorption of solutes in the thick ascending limb

A

Na/K ATPase on basolateral membrane
- salt pumped into medulla

Na/K/2 Cl cotransporter on the apical membrane
- all these ions pumped into the tubule cell

28
Q

What is the osmolarity of the medulla interstitial fluid?

A

300 - 1200 mOsm

29
Q

Describe the action of vasopressin

A
  1. ADH binds to V2 receptor
  2. G protein activated
  3. Activation of adenylate cyclase
  4. cAMP
  5. AQP2 inserted into the membrane
30
Q

Describe the osmolarity of the vasa recta

A

Follows the osmolarity of the region it is in

Near cortex: 300
Deep in medulla: 1200

31
Q

Where is the collecting duct?

Why is this important?

A

It drops down into the medulla

This means that if there are aquaporins present, water will move out of the collecting duct

BIOM20002 - HSF (60 decks)

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