9.4 Body Fluid; Blood Pressure Regulation, Electrolyte Balance & Renin-Angiotensin-Aldosterone System (RAAS)

Question 1

Are men or women made up of more water? Why does this make sense?

Answer 1

• Men
• Women have more fat; insoluble in water

Question 2

What percentage of body fluids are intracellular/extracellular?

Answer 2

• 2/3 Intra
• 1/3 Extra

Question 3

What percentage of extracellular fluids are interstitial/plasma?

Answer 3

• 80% Interstitial
• 20% Plasma

Question 4

Name three processes by which the body takes up water (from most to least)

Answer 4

• Ingested liquids
• Ingested foods
• Metabolic water (not regulated; generated in rxns)

Question 5

Where is water gain regulated? What is this input interpreted as?

Answer 5

• Hypothalamus
• Interpreted as drop in BP and blood volume

Question 6

Name four pathways of water loss from most to least

Answer 6

• Kidneys
• Skin
• Lung
• GI Tract

Question 7

How is fluid lost from the kidneys?

Answer 7

• Follows salt out

Question 8

Explain how water could be lost following a salty meal

Answer 8

• More Na+ and Cl- in the plasma
• Water from ICF -> ECF -> Plasma along osmotic gradient
• Hence, more water is excreted

Question 9

What are electrolytes?

Answer 9

Charged ions in solution

Question 10

What are the three functions of ions?

Answer 10

• Control osmosis
• Maintain acid-base balance
• Carry electrical currents

Question 11

What is the normal range of blood pH?

Answer 11

7.35-7.45

Question 12

Why is maintaining pH homeostasis important?

Answer 12

Without it, active site becomes denatured and protein loses function

Question 13

Symptoms of acidosis

Answer 13

Depresses CNS -> coma

Question 14

Symptoms of alkalosis

Answer 14

Excites CNS -> Spasms, convulsions, death

Question 15

How do buffer systems increase/decrease pH?

Answer 15

Absorb/release H+ ions through chemical reactions

Question 16

How do the lungs influence pH?

Answer 16

• Inc resp rate: increased carbonic acid breakdown, increased removal of H+
• Dec resp rate: decreased carbonic acid breakdown, increased H+ in blood

Question 17

How do the kidneys influence pH?

Answer 17

• Increase secretion/excretion of H+
• Conserve H+ and release bicarbonate instead

Question 18

Aldosterone vs ADH

Answer 18

ADH: Aquaporins -> water reabsorption
Aldosterone: sodium -> osmotic gradient -> water

Question 19

What does the macula densa “taste” for?

Answer 19

Sodium or chloride

Question 20

Which cells in the Juxtaglomerular apparatus secrete renin?

Answer 20

JG Cells (from storage granules)

Question 21

What is renin?

Answer 21

Enzyme and hormone

Question 22

What is the effect of Ang II produced following renin release on the vasculature of the nephron?

Answer 22

• Constricts afferent arteriole
• Constricts efferent arteriole more, creating back-pressure

Question 23

What does the macula densa release if salt is too high/low?

Answer 23

High: Adenosine (inhibits renin)
Low: signals JG cells to secrete renin

Question 24

What is the effect of adenosine on blood vessels in the kidney?

Answer 24

Constricts Afferent arteriole

Question 25

Other than renin release, how else can the juxtaglomerular apparatus adapt to decreased salt?

Answer 25

Release of vasoldilators (e.g. nitric oxide), allows more blood to flow into the glomerulus, thus increasing filtration rate

Question 26

What is the effect of SNS activation of the mesangial cells? How does this affect GFR?

Answer 26

• Mesengial cells contract
• Reduces glomerular surface area
• Reduces GFR

Question 27

Where is angiotensinogen produced?

Answer 27

The liver

Question 28

Where is ACE most common?

Answer 28

The lungs

Question 29

Does angiotensin II always trigger aldosterone release?

Answer 29

No; only sufficiently high levels

Question 30

List three effects of angiotensin II (other than aldosterone release)

Answer 30

• Thirst -> Water intake
• Vasopressin release -> increased water resorption
• Arteriolar vasoconstriction