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Physiology Renal ABS 2018 > Urine Concentration and ECF Osmolarity > Flashcards

Urine Concentration and ECF Osmolarity Flashcards

1
Q

What are the 2 main ways to concentrate urine?

A
  1. ADH
  2. Eliciting a thirst response
    Both of these will decrease osmolarity in the blood & created more concentrated urine.
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2
Q

Exaplain how ADH works.

A
  1. Starts in hypothalamus- which have osmol receptors
  2. they sense osmolarity- They regulate the POSTERIOR pituitary gland
  3. Changes is osmolarity cause changes in the post. pituitary.
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3
Q

What factors are necessary for creating concentrated urine?

A
  1. ADH
  2. Functioning loop of Henle-
    a. Concentrating segment= descending limb
    b. Diluting segment= ascending limb
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4
Q

What are the 2 types of nephrons? The length of what is important? Why?

A
  1. Cortical- shorter loop of Henle
  2. Juxtamedullary- longer loop of Henle
    - It’s role is to create a concentration gradient!
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5
Q

What is the most dilute your nephron osmolarity can get to? why? Most concentrated? Why?

A
  1. Most dilute: 150 - in the ascending limb

2. Most Concentrated: 1200 - as you go down the descending loop of Henle

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6
Q

What occurs in the presence of ADH?

A
  1. ADH opens aquaporin channels
    - water only leaves the neprhon if it is more concentrated inside the nephron than the outside– only way H2O can leave the nephron and go into ISF.
  2. Osmolarity of urine will be hypertonic
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7
Q

What happens in the absence of ADH?

A
  1. water remains in the urine because there is NO ADH to open aquaporin channels.
  2. Osmolarity of urine will be hypotonic
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8
Q

What will be our osmolarity when we enter the collecting duct? Does it change if we do or do not drink a lot of water?

A

Osmolarity= 150 mOsm/L ALWAYS

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9
Q

What happens on the ascending loop of Henle. Why is it important?

A

1.Reabsorption with
Na/2Cl/ K transporter
2. Can pump something against a 200 mOsm gradient (Tmax of htat particular transporter. )

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10
Q

Explain Medullary Countercurrent multiplier system.

A

1.Everything starts off as ISOOSMOTIC in the Loop of Henle
2. Ascending limb has Na/K/2 Cl transporter- move solutes out of nephron and into ISF. – has a transport max based on 200 mOSm — more concentrated outside than inside.
3. Descending limb has no transporters - H2O can move out though. – will equibrilize with ISF by water flowing out of Descending limb
4.

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11
Q

Explain Medullary Countercurrent multiplier system.

A
  1. Everything starts off as ISOOSMOTIC in the Loop of Henle
  2. Ascending limb has Na/K/2 Cl transporter- move solutes out of nephron and into ISF. – has a transport max based on 200 mOSm — more concentrated outside than inside.
  3. Descending limb has no transporters - H2O can move out though. – will equibrilize with ISF by water flowing out of Descending limb
  4. Fluid shifts– now we have fluid from ascending limb go into distal tubule
  5. Transporters will work now. tries to find those areas without a 200 mOsm difference and move SOLUTES out (make nephron in Ascending limb more diluted.)
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12
Q

What does urea do to the concentration gradient?

A

It helps add to it.

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13
Q

What does urea do to the concentration gradient?

A

It helps add to it- in addition to Na, K and 2 Cl.

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14
Q

What is an important structure for the function of the loop of Henle?

A

The Vasa Recta- allow concentration gradient to exist- PRESERVATION of the conecentration gradient

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15
Q

What’s the function of the Vasa Recta ? Name 2 ways it does this.

A

Function= To preserve the hyperosmolarity of the renal medulla (preserve concentration gradient)

  1. LOW BLOOD FLOW- VERY SLOWLY
  2. COUNTERCURRENT EXcCHANGER
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16
Q

Why is the loop of Henle labeled as a countercurrent multiplier?

A
  1. 2 currents go opposite of one another (ascending and descending)
  2. exchange of solutes and H2O
17
Q

Why are Vasa Recta labeled as countercurrent exchangers?

A

Only allow exchange of solutes

18
Q

How does the Vasa Recta work?

A

Make sure solutes in medulla do not leave and go into the blood.

19
Q

What 4 factors contribute to the concentration of urine?

A
  1. ADH plasma levels
  2. Concentration gradient
  3. Urea recycling
  4. Vasa Recta
20
Q

How do we balance fluids?

A

What comes in must come out.. Fluid In= Fluid Out

21
Q

What is your average daily fluid intake? Output?

A

intake: 2.5 L/day

Output 1.5-2 L/day

22
Q

What are insensible losses? What makes it up? When will you have more of this?

A
  1. When you breathe- you must use fluid to humidify air (100%) and lose fluid-
  2. Skin and Respiratory tract
  3. More insensible losses in hot, dry areas vs. humid areas.
23
Q

What happens during an excess ingestion of H2O?

A
  1. Osmolarity decreases
  2. ADH levels decrease
  3. Decreased Volume of Urine
  4. Increased urine osmolarity (concentrated urine)
24
Q

What happens if we increase volume without changing osmolarity?

A

Increased ECF

want to excrete it in the urine - but it takes urine flow rate longer to increase when the osmolarity is the same.

25
Q

How do we control urine output?

A

Controlling Na levels

  1. increase urine output by increasing Na levels.
  2. Decrease urine output by decreasing Na levels.
26
Q

Excretion of Na=?

A 
E(Na)= F - R
measure how much Na is excreted by lookin at how much is 
1. Reabsorbed
2. Filtered (*SAME AS  
FL= GFR 
SO.. E(Na)= (GFRxP)- R
27
Q

Na and high GFR relationship?

A

Increases in GFR will increase Filtered load of NA– AKA increasing amount of NA excreted

28
Q

Na and low GFR?

A

Decreased GFR - decreases filtered load and decreasing excretion of Na

29
Q

Name 4 ways to alter Na reabsorption in the body? Explain each.

A
  1. SNS
  2. RAAS
  3. Aldosterone
  4. ANP
30
Q

Explain 3 ways SNS change Na levels.

A
  1. Increased renin
  2. Vasoconstriction of afferent and efferent arterioles- decreases GFR
  3. Na reabsorption in PT- don’t know which transporter it uses
31
Q

Explain 3 ways aldosterone can change Na levels. where in the nephron?

A

OCCURS IN THE DISTAL TUBULE!

  1. Increase NA/K ATPAses on basolateral membrane
  2. Increase Na channels on apical membrane
  3. Also opens K channels on the apical membrane for K excretion.
  4. Increase Na and H2O reabsorption in the DT
32
Q

Explain 2 ways Angiotensin II changes Na levels.

A
  1. Cause Na reabsorption

2. Increase Na/H exchangers in the PT- to increase NA reabsorption and alters acid base balance.

33
Q

Explain how ANP changes Na levels?

A
  1. atrial natriuretic peptide - ONLY hormone that will decrease Na reabsorption.
  2. Released from the atria in response to stretch (high Blood pressure)
  3. turns off aldosterone
  4. turns off renin
  5. turns off ADH
34
Q

Explain how ADH changes Na levels? where in the nephrone

A

WORKS IN THE DISTAL TUBULE

  1. Same actions as aldosterone (increase Na reabsorption, H2O reabsorption)
  2. Open Na channels on the apical membrane
35
Q

What is volume contraction?

A

Decreased volume due to dehydration

  • osmolarity is increased
  • decreased blood volume
  • decreased blood pressure
36
Q

What is volume expansion?

A

Increased volume- due to ingestion of excess fluids.

  • high BV/BP
  • low osmolarity
  • increased ANP
  • decreased Angiotensin II/ADH/ Aldosterone

Physiology Renal ABS 2018 (7 decks)

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