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Physiology Final Exam > Fluid & Acid-Base Balance > Flashcards

Fluid & Acid-Base Balance Flashcards

Ch 15

1
Q

Is most body fluid in the ICF or ECF?

A

ICF

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2
Q

What are the main ions in the ECF? What are the main ions in the ICF?

A

ECF: mostly Na+, Cl-, HCO3-
ICF: mostly K+, PO43-, protein anions, small amount of Na+

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3
Q

What two things are regulated to maintain fluid balance in the body?

A

ECF volume and osmolarity

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4
Q

What does maintaining ECF volume do?

A

maintains arterial blood pressure

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5
Q

What does maintaining osmolarity do?

A

prevents swelling or shrinking of cells

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6
Q

What two long-term control measures are used to maintain blood pressure in the face of changes in ECF volume?

A
  • Control of thirst; inc or dec input of fluids
  • Control of salt in the body (Na+ load); retain or excrete H2O
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7
Q

Why does control of salt load go along with control of fluid volume?

A

increase salt always leads to water retention

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8
Q

How is salt load regulated in the body?

A
  • Changing the amount of Na+ filtered at the kidneys (sympathetic control over glomerular filtration rate)
  • Changing the amount of Na+ reabsorbed at the kidneys (hormonal control over reabsorption; renin-angiotensin-aldosterone system)
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9
Q

Hypertonicity

A

when water is lost but not solutes (dehydration)

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10
Q

Hypotonicity

A

when water is gained without solutes being gained (over hydration)

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11
Q

What does a hypotonic cell look like?

A

cell swells —> water enters cell; could burst if swells too much

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12
Q

What does a hypertonic cell look like?

A

cell shrinks –> water leaving the cell

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13
Q

What is metabolic H2O?

A

Cellular respiration produces CO2 and H2O
- created through metabolism, by oxidizing energy containing substances

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14
Q

Insensible loss of H2O?

A

loss due to breathing out air humidified in lungs or constant diffusion of H2O through skin cells and evaporated

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15
Q

How is control of ECF osmolarity mediated?

A

control of thirst (input) & kidney secretion (output)

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16
Q

Hypothalamic osmoreceptors

A

cells that monitor ECF osmolarity
- can stimulate vasopressin secretion and thirst center

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17
Q

Where is the thirst center?

A

Nucleus of cells in hypothalamus

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18
Q

How does vasopressin lead to INC water reabsorption? (review)

A

Vasopressin secreted –> binds to receptors on collecting ducts in kidney –> triggers insertion of aquaporins in cell membrane –> enhances permeability of collecting duct cells to water –> more water reabsorbed from urine

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19
Q

What happens during excess fluid intake?

A

Excess fluid intake –> decreased vasopressin secretion –> increased urinary output

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20
Q

Acid

A

pH lower than 7
- Acids dissociate in water and increase H+

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21
Q

Base

A

raise pH above 7
- dissociate in water and decrease H+

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22
Q

pH of water? pH of body fluids? how much deviation of pH can we tolerate?

A

pH water = neutral (7)
pH body fluids = 7.4, slightly basic
pH can deviate between 6.8-8.0 before death

23
Q

What does it mean that an acid is “strong” or “weak”? How does this relate to its dissociation constant (K)?

A
  • proportion of molecules that dissociate determine whether an acid is strong or weak

Dissociation constant (K) greater = stronger acid

24
Q

3 main sources of H+ in the body? Largest?

A

1) carbonic acid formation (MAJOR)
2) Inorganic acid by-products produced during the breakdown of dietary proteins in meat, grain, dairy
3) Organic acids produced during intermediary metabolism

25
Q

Respiratory Acidosis (example of carbonic acid formation)

A

external respiration doesn’t keep up with CO2 production = increased H+

26
Q

Respiratory alkalosis (example of carbonic acid formation)

A

external respiration outpaces CO2 production = decreased H+

27
Q

Respiratory acidosis vs. metabolic acidosis

A

Metabolic acidosis: H+ increases due to non-respiratory reasons

Respiratory acidosis: external respiration doesn’t keep up with CO2 production

28
Q

Three body defenses against changes in pH of body fluids

A

1) Chemical buffer systems
2) Respiratory mechanism
3) Renal mechanism

29
Q

Chemical [buffer] system

A

mixture of two chemical compounds in solution that [MINIMIZE] pH changed when either an acid/or base are added to solution

** Important example: H2CO3 <–> H+ (+) HCO3−

30
Q

HCl (strong acid) added to unbuffered H2O

A

nearly all H+ dissociate = very low pH

31
Q

HCl added to H2O with buffer

A

addition of dissociated H+ shifts the buffer equation to the left = much less H+ left dissociated = pH not as low

32
Q

How fast do buffers act? what are other buffers in the body?

A

within a fraction of a second

  • other buffers include: protein (ICF/ECF buffer), hemoglobin (buffer against carbonic acid changes), phosphate (urinary buffer, buffers ICF)
33
Q

Regular cellular respiration, red blood cells, and pulmonary capillaries

A

Cell Resp: nutrients + O2 –> CO2 + H2O

Red blood cells: CO2 + H2O –> H+ + HCO3- (H+ added)

Pulmonary capillaries: H+ + HCO3- –> CO2 + H2O (H+ taken away; expiration removes H+ forming that results from cellular respiration)

34
Q

metabolic acidosis

A

H+ increases due to non-respiratory reasons

35
Q

metabolic alkalosis

A

H+ decreases due to non-respiratory reasons

36
Q

how does body respond to metabolic acidosis? (H+ increases)

A

1) Buffering by H2CO3: HCO3- system: buffer reaction shifted to the left (H2CO3 <– H+ + HCO3-)

if buffering isnt sufficient in normalizing pH…

2) Ventilation increases:
more CO2 exhaled = H+ (+) HCO3- –> CO2 (+) H2O
(shifted more to the right; normalizes pH)

37
Q

how does body respond to metabolic alkalosis? (decrease in pH)

A

1) buffering by H2CO3:HCO3- system: buffer reaction shifts to the right (H2CO3 –> H+ HCO3-)

if buffering isn’t sufficient…

2) Ventilation decreases –> less CO2 exhaled –> (H+ + HCO3- <– CO2 + H2O) shift to the left; normalizes pH

38
Q

Under a normal functioning respiratory system, does [H+] continually increase? Why or why not?

A

[H+] does not continually increase; the respiratory system actively regulates the level of hydrogen ions (H+) in the blood by adjusting the rate and depth of breathing to maintain a stable pH level through the removal of carbon dioxide (CO2), which is a key factor in H+ production.

39
Q

Inorganic and organic acids produced through digestion and metabolism giving us…

A

constant source of H+ (separate from CO2) –> kidneys must excrete extra H+

40
Q

What is filtered into Bowman’s capsule at the glomerulus? Which is there more of?

A

H+ and HCO3- (much more HCO3-)

  • Both are implement to tubular cells
  • filtered HCO3- reabsorbed into tubular cells in (INDIRECT way
41
Q

______ secretes more H+ out of tubular cells than there are HCO3- in the filtrate

A

Active transport

42
Q

When extra H+ is secreted, coupled with ____ of newly produced HCO3-

A

absorption

43
Q

H+ in urine buffered by _______ buffer system to reduce ____

A

phosphate; acidity

44
Q

In BODY tissues: extra H+ produced, _____ removed from solution

A

HCO3-

45
Q

At kidneys: ___ excreted, ____ put back into solution

A

H+ excreted; HCO3- put back into solution

46
Q

Is all filtered HCO3- excreted or reabsorbed?

A

almost all HCO3- is reabsorbed

47
Q

How does H+ secretion play a role in HCO3- reabsorption?

A

Active transport secretes lots of H+ –> couples with absorption of newly produced HCO3- –> extra HCO3- absorbed into capillaries

48
Q

Is more of less H+ secreted than HCO3- filtered into the filtrate

A

MORE

49
Q

Secretion of H+ into the tubule is coupled with what?

A

Secretion of extra H+ is coupled with absorption of newly produced HCO3− ; extra HCO3− gets absorbed into capillaries

50
Q

What are the two buffers in the urine that help bring up the pH of urine?

A

1) Phosphate buffer system

~During acidosis (inc H+) phosphate buffers maxed out…

2) Tubular cells secrete ammonia (NH3) as additional buffer (NH3 + H+ –> NH4+)

51
Q

During acidosis, what happens to H+ and HCO3- in the kidneys?

A

kidneys excrete additional H+; goes along with creation of additional HCO3-

52
Q

During alkalosis, what happens to H+ and HCO3- in the kidneys?

A

kidneys excrete HCO3-, goes along with creation of H+

53
Q

How long does it take renal regulation of pH to kick in?

A

takes hours to days to compensate
- completely restore pH to normal (unlike others)
- compensates for respiratory AND metabolic acidosis and alkalosis

Physiology Final Exam (3 decks)

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