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PHGY 4 > Mod 5 > Flashcards

Mod 5 Flashcards

1
Q

Define - Acid

A

Acid: hydrogen containing substances that when in solution dissociate into H+ and an anion

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2
Q

What makes a strong acid

A

the mroe H+ that dissociate, the stronger the acid

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3
Q

Define - base

A

Base: substances that bind free H+ and remove it from solution

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4
Q

What does pH express, what is the equation

A

pH = the amount of H+ in solution
pH = log10 (1/H+)

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5
Q

At what pH is blood considered acidosis

A

less than pH 7.35

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6
Q

At what pH is blood considered alkalosis

A

less than pH 7.45

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7
Q

Name the bodies 4 buffer systems

A
  1. The [H2CO4]:[HCO3] buffer system
  2. The protein buffer system
  3. The hemoglobin buffer system
  4. The phosphate buffer system
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8
Q

What is the most important buffer pair in the body

A

The H2CO3:HCO3- Buffer Pair

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9
Q

What does the H2CO3:HCO3- Buffer Pair buffer against

A

Is responsible for buffering pH changes arising from everything other than CO2-generated H2CO3

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10
Q

Why is the H2CO3:HCO3- buffer so effective?

A

1) Both H2CO3 and HCO3- are present in high quantities in the ECF, meaning this system has a high capacity for buffering changes in pH
2) Both H2CO3 and HCO3- are highly regulated in the body to keep their concentrations relatively stable. The kidneys regulate HCO3- while the respiratory system regulates H2CO3 by regulating CO2

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11
Q

What does the Henderson-Hesselbalch equation define?

A

Defines the relationship btwn H+ and a buffer system pair
- allows you to calculate the pH around which the buffer pair works

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12
Q

Why are proteins such great buffers?

A
  • proteins contain aa with acidic and basic groups which can give and take H+
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13
Q

Where are proteins buffers the most important

A

intracellular fluids bc inside cells is protein rich

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14
Q

What is the hemoglobin buffer system

A
  • Is an essential buffer of H+ generated from metabolically produced CO2
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15
Q

What would happen if we didn’t have the hemoglobin buffer system

A

The venous blood would become too acidic

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16
Q

How does hemoglobin buffer system operates to ensure venous blood doesn’t become too acidic

A

CO2 in Plasma: as CO2 leaves the tissue and enters the blood, most of it forms H2CO3 in the RBCs with the help from the enzyme carbonic anhydrase

O2 in Plasma: Most of this H+ will immediately bind to Hemoglobin and no longer add to the acidity of the body fluids. This frees up the oxygen bound to the hemoglobin so it is released to the tissues

HCO3- in Plasma: some of the H@CO3 will immediately dissociate into HCO3- and H+

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17
Q

Where is the phosphate buffer system important?

A

The most important role for the phosphate buffer system is to buffer the pH of urine
- is the only buffer system in urine

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18
Q

How does the respiratory system adjust pH

A

inhalation and exhalation

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19
Q

How much more H+ does the respiratory system remove than the kidneys’

A

100x more

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20
Q

The Kidneys are particularly important for removing H+ produced by

A

sulfuric, phosphoric and lactic acid

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21
Q

Kidneys help control the pH of extracellular fluid in 3 ways:

A

1) The excretion of H+
2) The excretion/reabsorption of HCO3-
3) The secretion of ammonia

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22
Q

Where does the H+ excreted in urine come from?

A

Almost all the H+ that is excreted in the urine comes from tubular secretion in the proximal, distal, and collecting tubules

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23
Q

Steps of renal secretion:

A

1) CO2 enters the tubular cells either from the plasma, the tubular fluid, or metabolically produced within the tubular cells
2) Within the cells, CO2 and H2O, under the influence of intracellular carbonic anhydrase, form H2CO3, which dissociates into H+ and HCO3-
3) An energy dependent carrier on the luminal membrane will then transport H+ into the tubular fluid

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24
Q

Is the secretion of H+ neural or hormonally controlled?

A

Neither - The secretion of H+ is directly related to the acid-base status of the ECF, there is no neural or hormonal control

25
Q

What happens when the [H+] passing thru the peritubular capillaries is greater than normal

A

the tubular cells increase the secretion of H+

26
Q

The kidneys regulate plasma [HCO3-] in 2 ways:

A

1) Thru reabsorption of HCO3- back into plasma

2) Addition of “new” HCO3- to the plasma

27
Q

How is renal HCO3- reabsorbed?

A

1) HCO3- in the tubular fluid combines with secreted H+ to form H2CO3. H2CO3 then breaks down into CO2 and H2O, both of which can cross the luminal membranes
2) Once inside a tubular cell, carbonic anhydrase converts the CO2 and H2O back into H2CO3, which then freely dissociates into HCO3- and H+
3) HCO3- can cross the basolateral membrane so it leaves the cell and H+ is again secreted. A greater amount of h+ is secreted than HCO3- filtered. This means all of the filtered HCO3- is normally reabsorbed, as H+ is available to combine with it to form highly absorbable CO2

28
Q

Tubular cells can produce “new” HCO3- … how

A

1) CO2 from the plasma and tubular cell metabolism, along with hydroxyl radical from the dissociation of H2O, is converted in to HCO3- within the tubular cells where it is transported across the basolateral membrane into the plasma
2) H+ is released from the dissociation of water and this H+ is then secreted into the tubular lumen where it combines with the urinary buffers, usually basic phosphate, and then excreted from the body

29
Q

At what pH can tubular cells no longer secrete H+ into the tubular fluid

A

pH 4.5

30
Q

There are 2 important urinary buffers:

A

There are 2 important urinary buffers:

1) Phosphate
§ Dietary basic phosphate is freely filtered for elimination
§ Once in the tubular fluid, any H+ that it buffers will be excreted from the body
§ Bc the primary purpose of basic phosphate filtration is to remove excess phosphate from the body, its not really regulating tubular acidity
§ Since there is no mechanism to increase the amount of basic phosphate added to the tubular fluid, it has a limited buffering capacity

2) Ammonia
§ Under acidic conditions, when the phosphate buffer system has been overwhelmed, the tubular cells secrete ammonia (NH3) into the tubular fluid
§ The NH3 reacts with H+ to form ammonium ion (NH4+)
§ NH4+ is not reabsorbed so it is excreted in the urine, thereby removing an H+ from the body
§ NH3 is actively synthesized and secreted by the tubular cells proportionately to the amount of excess H+

31
Q

Which system has a limited capacity to resist acid/base imbalances?

A

Buffers

32
Q

Which system prevents free H+ from contributing to fluid pH

A

buffers

33
Q

Which system removes excess H+ from metabolic sources

A

renal

34
Q

Which system removes H+ derived from carbonic acid

A

respiratory

35
Q

Which system is a second line of defense

A

respiratory

36
Q

Which system is involved in regulating plasma [HCO3]

A

renal

37
Q

The ratio of [HCO3-] to [CO2] is normally

A

20:1

38
Q

A change in pH caused by the respiratory system will have:

A

an abnormal [CO2], which in turn causes a change in carbonic acid-generated H+

39
Q

A change in pH caused from metabolism will have:

A

an abnormal [HCO3-] resulting from an inequality in the amount of HCO3- available and the amount of H+ generated from non-carbonic acid sources that the HCO3- must buffer

40
Q

When the [HCO3-]:[CO2] ratio falls below 20:1, this will cause:

A

Acidosis

41
Q

When the [HCO3-]:[CO3] ratio rises above 20:1, this will cause

A

When the [HCO3-]:[CO2] ratio rises above 20:1, this will cause alkalosis

42
Q

When does respiratory acidosis occur?

A

Respiratory acidosis occurs when there is a buildup of CO2 in the plasma, which causes the [HCO3-]:[CO2] ratio to be below 20:1
- hyperventilation

43
Q

Emphysema, chronic bronchitis, asthma, severe pneumonia and metabolic acidosis - can all cause

A

respiratory acidosis

44
Q

How is respiratory acidosis compensated

A

To compensate for respiratory acidosis:
- The chemical buffers immediately start taking up the extra H+
- The kidneys secrete more H+ while both reabsorbing HCO3- and generating new HCO3-

45
Q

What causes respiratory alkalosis?

A

Occurs when there is an increase in ventilation that causes the [CO2] in the plasma the decrease below normal

46
Q

Fever, anxiety, sever infections - can all cause

A

respiratory alkalosis

47
Q

How is respiratory alkalosis compensated for?

A

To compensate for respiratory alkalosis:
- The chemical buffer system releases H+
- The respiratory system responds by decreasing ventilation
- If the respiratory alkalosis persists for a few days, the kidneys will compensate by decreasing H+ secretions and increasing HCO3- secretion

48
Q

What characterizes metabolic acidosis

A

Is always characterized by a decrease in [HCO3_] and a normal [CO2]

49
Q

How do you determine the cause of metabolic acidosis

A

measure the anion gap

50
Q

What causes a low anion gap (less 8)

A

Uncommon and generally results from the loss of plasma albumin, such as during haemorrhage

51
Q

What causes a normal anion gap?

A

Means there is a loss of HCO3-, which can be caused by diarrhea and some renal diseases
○ There is generally a compensatory increase in [Cl-] to conserve electrical neutrality

52
Q

What causes a high anion gap

A

○ Indicates that the metabolic acidosis is caused by an increase in the unmeasured anions, which causes a decrease in [HCO3-] as it is used up for buffering the acids

53
Q

What are the 4 common causes of metabolic acidosis

A

○ Severe diarrhea:
§ The digestive juices are rich in HCO3- that is secreted to aid in digestion but later reabsorbed
§ During diarrhea, this HCO3- may be eliminated before it can be reabsorbed, which causes a drop in [HCO3-], decreasing the buffer capacity of the plasma as well as causing more bicarbonate to dissociate and release H+

○ Diabetes Mellitus
§ Without insulin, glucose does not enter most cells, so they revert to fat metabolism to generate ATP
§ This cases an increase in keto acids, which raises the anion gap

○ Strenuous exercise
§ When muscles resort to anaerobic metabolism, excess lactate is produced which raises plasma H+
§ The lactic acid will also raise the anion gap

○ Uraemic Acidosis
§ Uraemia is severe renal failure
§ With decreased renal function, the kidneys can’t excrete the excess H+ produced from metabolism so the [H+] increases
There is generally a loss of HCO3- as well, causing an increased anion gap

54
Q

How is metabolic acidosis compensated for

A

○ For all these except uremic acidosis, compensation can occur by the buffers taking up the extra H+, the lungs blowing off extra CO2. and the kidneys secreting more H+ and conserving HCO3-

55
Q

What is metabolic alkalsis

A
  • Is a reduced [H+] caused by a decrease in non-carbonic acids
55
Q

What causes metabolic alkalosis

A
  • vomiting
  • ingestion of alkaline drugs
56
Q

How is metabolic alkalosis compensated for?

A

○ To compensate for metabolic alkalosis, the chemical buffer system immediately liberate H+
○ ventilation reduces to raise plasma CO2
○ If it persists over several days, the kidney decrease H+ secretion and increases HCO3- secretion

57
Q

When there is an increase in plasma [H+] above normal, which of the following describes the response of the kidneys?

A

Formation of new HCO3-

58
Q

With regards to the influence of the respiratory system on plasma pH, which one of the following occurs during hyperventilation?

A

Alkalosis

PHGY 4 (3 decks)

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