Lecture 18: Integration salt and water balance 2

Question 1

Where is aldosterone released from?

Answer 1

Adrenal gland

- zona glomerulosa cells of the adrenal Cortex

Question 2

Where is ACE released from?

Answer 2

lungs

Question 3

Where is angiotensinogen released from?

Answer 3

Liver

Question 4

What causes aldosterone release?

Answer 4

1. Most powerful: K+ conc (ECF)

2. Angiotensin II

Question 5

Aldosterone action cellularily

Answer 5

1. Aldosterone binds to non-specific MC mineralocorticoid receptor from intersitial side (spironolactone competitive inhibition)
2. events in nucleus
3. ENac channel causes increased sodium reabsorption into cell
4. Na finally pushed into ECF via NaK ATPase
5. Decreased potassium levels

Question 6

What competitively inhibits MC receptor on interstitial side?

Answer 6

Spirolactone

Question 7

What competitively inhibits ENaC channel on tubular lumen side?

Answer 7

Amiloride

- K sparing diuretic

Question 8

Normally aldosterone stimulates the reabsorption of 33g of NaCl daily.
If patient loses 10% adrenal function –> will 33g of NaCl be excreted per day indefinitely?

Answer 8

System has compensation/redundancy: if there is an inappropriate angiotensin of aldosterone response –> there is enough backup to continue (even though not being as ideal)
Sodium loss –> stimulates Na retention mechanisms –> adrenal gland cortex failure results in inability to secrete aldosterone
Other factors will continue to try –> decrease GFR –> increased Na reabsorption (partially)

Question 9

Regulation of ecf Osmolality

Answer 9

osmolality = tightly controlled = changes in ions

• REGULATED by H2O handling
• Mediator: ADH

Question 10

Regulation of ecf Volume

Answer 10

fluid volume = quanitity of water

• REGULATED by Na handling, as it drives water movement
• varies alot around the day -> therefore need lots of backup mechanisms (surrounding Na movement) to control ecf Volume
• -> Mediators:
  1. RAAS
  2. SNS

Question 11

Out of ecf osmolality and volume what varies more and what does this mean re its regulators?

Answer 11

1. ecf Volume varies throughout the day
   - -> this means that it requires More Regulator mechanisms (surrounding Na movement) to control its fluctuations
2. RAAS
3. SNS

Question 12

Why do you want to keep osmolality within tight range?

Answer 12

Brain cells dont like changes in osmolality

hyper/hypo osmolality –> nausea, headaches, confusion, lethargy, weakness, seizures

Question 13

Attempted suicide with soy sauce

Answer 13

Massive change in blood volume
All fluid has come out to try balance osmolality
- high Na in blood –>
- ADH levels decreased
- Renin decreased –> decreased reabsorption of Na
- small increase in Blood volume

Question 14

Hyponatremia in marathon runners

Answer 14

Historical advice: continually drink water

13% of runners had Hyponatremia (over hydrated)

Question 15

What happens when there is a High ECF volume?

Answer 15

Decreased reabsorption of Na

- as Na regulates ECF volume levels

Question 16

What increases Na reabsorption?

Answer 16

• 1. RAAS
• 2. SNS
     
     3. ADH

Question 17

What decreases NA reabsorption?

Answer 17

• 1. ANP
     
     2. Decreased RAAS and SNS
     3. dopamine
     4. prostaglandins

Question 18

ANP

Answer 18

released from heart in response to increased Pressure and Stretch on heart
28 aa

Question 19

What are the actions of ANP

Answer 19

1. Blocks ENac + Inhibits NaKATPase –> decrease DT Na reabsorption
2. Inhibits aldosterone release
3. Inhibits renin release
4. Vasodilates afferent arteriole –> increased GFR
5. Urodilation released by kidney (30 aa almost identical to ANP)
6. Dopamine released by PT neurons –> inhibition of PT NaKATPase and NaH exchanger
   Diagram**

Question 20

Homeostatic regulation

Answer 20

primarily negative feedback loops

Question 21

What are the 2x regulators of osmolality?

Answer 21

Osmolality is regulated by water change

1. osmorecetpors –> ADH from kidney
2. thirst –> brain/drinking behavior
   - - NEgative feed back

Question 22

What are the sensors and regulators of blood pressure changes?

Answer 22

Blood pressure: carotid sinus + aortic arch baroreceptors
Blood volume: atrial stretch receptors
Kidney effector
- Short term : BP
- long term: NA secretion

Question 23

What happens during dehydration?

Answer 23

Sensors:
Signals:
Effectors:
Eventual response:
Diagram**

Question 24

What happens when you eat alot of salty chips?

Answer 24

Sensors:
Signals:
Effectors:
Eventual response:
Diagram**
Step 1: Increased osmolarity –> decrease in osmalarity via increase in ECF
Step 2: Increased ECF –> excrete (slow) + rapid (blood pressure changes CVCC ANS)

Question 25

What is the relationship b/w SNS and Na levels

Answer 25

Increased Na levels –> decrease SNS activity –> decreases Volume

Question 26

What is the relationship b/w change in SNS and change in Blood PRessure

Answer 26

Even if Blood pressure doesn’t change
- SNS activity will change renal 1. RAAS system independently 2. vasoconstriction of afferent arteriole –> changes GFR (extrinsic mechanisms)

Question 27

What is the impact of a high salt pasta meal re angiotensin?

Answer 27

• high salt = high volume = decrease RAAS

Decreased angiotensin II –> decreased aldosterone –> decreased Na reabsorption

Question 28

Dehydrations relationship with ADH

Answer 28

Increased ADH

Question 29

What is the angiotensin response to hemorrhage if renal nerves to the kidney are denervated?

Answer 29

• hemorrhage –> decrease BP –> reduction in afferent arteriolar –> increased SNS

Question 30

Effects of increasing angiotensin II on salt and water in urine

Answer 30

Increased angiotensin II –> Increased reabsorption of Na and hence water –> decreased Na and water in urine

Question 31

What is the relationship b/w stenosis of the renal artery and sodium and water rebsorption

Answer 31

Stenosis of renal artery –> decreased flow into kidney –> increased water and sodium reabsorption