Control of Fluid balance

Question 1

What mechanisms contribute to water loss?

Answer 1

Insensible
Sweat
Feces
Urine

Question 2

What are the three local mechanisms of renal function?

Answer 2

Autoregulation (Myogenic and tubuloglomerular feedback)
Pressure Diuresis
Pressure Naturesis

Question 3

Why dosn’t the metabolic response affect the kidneys?

Answer 3

Renal autoregulation serves to keep GFR constant, whereas in other tissues auto regulation matches blood flow for metabolic needs

Question 4

What is the sensor and response in the tubuloglomerurlar feedback mechanism?

Answer 4

High/Low Na sensed by the macula densa cells, NO to afferent arteriole, angiotensin II to efferent arteriole and a decrease in tonic release of adenosine

Question 5

What is the mechanism of pressure diuresis and natriuresis?

Answer 5

Increased renal arterial pressure increases peritubular capillary hydrostatic pressure, increases renal interstitial fluid hydrostatic pressure Na and water in interstitial fluid leak back into tubular lumen AND decreased aldosterone less Na reabsorption water follows

Question 6

What type of receptors are the macula densa cells?

Answer 6

Stretch receptors, shrink or swell depending on sodium concentration (similar to Cosmo receptors)

Question 7

What three mechanisms are part of the neural regulation of renal function?

Answer 7

Cardiovascular reflexes
Renal sympathetic nerve
Osmoreceptors

Question 8

What is the neural response to low pressure/volume by the baroreceptors and volume receptors?

Answer 8

ADH secretion
ANG II
thirst promotion

Question 9

Where does the renal sympathetic nerve innervate?

Answer 9

The afferent and efferent arteriole

Question 10

What are the effects of renal sympathetic nerve stimulation?

Answer 10

Renal arteriole constriction, increased sodium reabsorption and increased ANG II (activation reduces sodium and water loss)

Question 11

Where are the osmoreceptors located?

Answer 11

Neurons in the AV3V region, they lack a BBB in order to sample ECF osmolarity

Question 12

What is the sensor and response of the osmoreceptors?

Answer 12

Swell shrink based on osmolarity and ADH inhibition/excretion

Question 13

Where are the thirst and salt appetite centers of the brain?

Answer 13

AV3V region

Question 14

What receptors are responsible to triggering thirst and salt appetite?

Answer 14

Osmoreceptors 
Baroreceptors and volume receptors (project to AV3V)
THIRST ONLY
Increased ANG II 
Dry mouth

Question 15

What inhibits the thirst response?

Answer 15

Distended stomach

Receptors in the mouth

Question 16

What is the most powerful regulator of ECF osmolarity and sodium concentration?

Answer 16

ADH-thirst

Question 17

What is the importance of aldosterone to salt and water retention?

Answer 17

Stimulates the Na/K ATP pump on tubular epithelial cell basolateral membrane (Na retention and K secretion)
MORE IMPORTANT K REGULATOR

Question 18

What hormone is considered the master of body fluid balance?

Answer 18

ANG II, most important hormone for Na retention (stimulates aldosterone secretion and ATP pump)

Question 19

What causes the release of ANP?

Answer 19

Increased atrial stretch, causes naturesis and water reabsorption is inhibited

Question 20

How does parathyroid hormone affect tubular reabsorption?

Answer 20

Increases tubular reabsorption of Ca at the distal tubules, inhibits phos (proximal) and promotes mag reabsorption (loop)

Question 21

Where is angiotensigenogen produced?

Answer 21

The liver

Question 22

Where is ACE produced?

Answer 22

Lungs (supply in kidney and brain for local RAAS system)

Question 23

What are other factors that can promote the release of ADH?

Answer 23

Nausea
Nicotine
Morphine
Alcohol
Haloperidol

Question 24

Which has a greater effect on body fluid balance salt intake or water intake?

Answer 24

Salt, special channels and pumps are required to move Na across membranes

Question 25

When there is an acute change in b/p what is the first mechanism to respond?

Answer 25

Neural: Chemoreceptors, baroreceptors, CNS ischemic response, activation of SNS

Question 26

What is the purpose of increasing TPR if you have a decrease in blood volume?

Answer 26

Shunt blood away from the periphery to the core

Question 27

When there is an acute change in b/p what mechanisms respond after minutes to the change?

Answer 27

RAS
Capillary fluid shift: ISF -> blood
Stress relaxation (NOT auto regulation)

Question 28

What is the mechanism behind the stress relaxation response?

Answer 28

When there is an increase in pressure followed by a decrease in pressure from changes in the orientation of elastic tissue fibers in smooth muscle of vessel or organ

Question 29

When there is an acute change in b/p what mechanisms respond after hours/days to the change?

Answer 29

Renal body fluid mechanisms: Aldosterone
Diminishing baroreceptor (resets)
Capillary fluid shift contribution

Question 30

Does RAAS affect salt appetite or thirst?

Answer 30

Yes, on a local level the brain’s RAAS system stimulates SFO neurons

Question 31

How does the RAAS move arterial pressure regulation to a new set point?

Answer 31

Change in salt/water output (renin)

Change in salt/water intake (thirst salt)

Question 32

Why are ACE inhibitors an effective treatment for most HTN patients?

Answer 32

The origin of most HTN is an overactive RAAS system