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Human Physiology Y3 > Acid-Base > Flashcards

Acid-Base Flashcards

1
Q

Define acid and base

A

Acid = molecules that can release H+
Base = ion or molecule that can accept H+

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2
Q

What is the arterial blood pH?

A

7.35-7.45

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3
Q

What is urine pH and why does it range?

A

4.5 - 8
Ranges depending acid-base status of EFC
In order to tightly regulate body pH

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4
Q

What are the pH limits a person can live for a few hours?

A

6.8 - 8

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5
Q

Define acidosis

A

Arterial pH below 7

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6
Q

Define alkalosis

A

Arterial pH above 7.4

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7
Q

What systems regulate the body pH?

A

Kidneys
Lungs

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8
Q

Define a buffer

A

Substance that can bind or release H+ to keep pH of solution relatively constant despite addition of considerable acid or base

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9
Q

Name 4 buffers

A

H2CO3
H2PO4-
HProt
HHb

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10
Q

What does amino acid metabolism create?

A

Releases NH4+ and H2SO4 (sulfuric acid)

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11
Q

How does the kidney regulate acid-base balance?

A

Excretes acids
Conserves HCO3-

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12
Q

Where does H+ secretion and HCO3- reabsorption NOT occur?

A

THIN segment of loop of Henle

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13
Q

What effects do carbonic anhydrase inhibitors have?

A

Decrease proximal tubular H+ secretion»>Increase fluid excretion»>Increase loss of bicarbonate and Na+

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14
Q

What cells are found in the DCT?

A

Type A Intercataled cells

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15
Q

How is HCO3- reabsorbed in the DCT?

A

HCO3- / Cl- exchanger

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16
Q

How is H+ secreted in the DCT?

A

Mainly H+ ATPase mediated by ALDOSTERONE
H+/K+ ATPase

17
Q
A
18
Q

What happens when urine pH reaches 4.5?

A

Limiting pH = further H+ secretion is not possible

19
Q

What is the role of buffering systems in terms of urine pH?

A

3 systems bind H+ in the urin
Allow more H+ secretion
Delay reaching limiting pH

20
Q

What are the 3 buffering systems in urine?

A

Bicarbonate buffer system
Phosphate buffer system
Ammonia buffer system

21
Q

Where does each buffering system in urine occur?

A

Bicarbonate = mostly PCT
Phosphate = DCT & CT
Ammonia = PCT & DCT

22
Q

What is the ratio between HCO3- and phosphate?

A

New HCO3- is returned to the blood for each NaHPO4 rate reacts with a secreted H+

23
Q

How does the ammonia buffer work?

A

Glutamine is taken up by the proximal tubular cell
It splits into 2HCO3- and 2NH4-
The NH4+ is secreted into tubular lumen by NH4- / Na+ exchanger
NH4+ joins with Cl-

24
Q

What factors interfere with H+ secretion and HCO3- reabsorption?

A

CO2
Ang II
Aldosterone
Serum K+ levels
ECF volume

25
Q

Why does high CO2 increase H+ secretion and HCO3- reabsorption?

A

Increases the carbonic acid levels = enhanced H+ secretion

26
Q

How does increased aldosterone increase H+ secretion and HCO3- reabsorption?

A

Stimulates H+ secretion by Type A intercalated cells of the DCT

27
Q

How does decrease in ECF volume increase H+ secretion and HCO3- reabsorption?

A

Activates RAAS -> increasing H+ secretion -> alkalosis

28
Q

How does increase in Ang II increase H+ secretion and HCO3- reabsorption?

A

Ang II enhances the activity of the sodium-hydrogen exchanger (NHE3) located on the luminal membrane of PCT cells

Leading to increased secretion of H+

29
Q

How does ventilation regulate acid-base balance?

A

Increase ventilation = eliminates CO2 = decrease in H+ concentration

30
Q

How is bicarbonate lost and what does this cause?

A

Metabolic acidosis

Diarrhoea
Renal tubular acidosis type 2 (RTA2)

31
Q

How is metabolic acidosis caused?

A

Ingestion of acidifying salts = NH4Cl and CaCl2
Decreased H+ excretion = renal failure or RTA1
Increased H+ production = diabetic ketosis and lactic acid generation

32
Q

What are the causes of metabolic alkalosis?

A

Loss of H+ = vomiting & diuretics
Ingestion of HCO3- = ex-antacids

33
Q

What are the causes of respiratory acidosis?

A

Decreased ventilation = due to lung diseases or neuromuscular problems (leading to respiratory muscle weakness)

Severe pneumonia / asthma

34
Q

What are the causes of respiratory alkalosis?

A

Increased ventilation = due to hyperventilation of physiology

Physiology = high altitudes so low O2 level stimulates respiration

35
Q

What happens in chronic acidosis?

A

Regardless of what type of acidosis = increased production of NH4+ which contribute to excretion of H+ and addition of new HCO3- to the extracellular fluid

36
Q

What limits respiratory compensation of metabolic alkalosis?

A

Size of this compensation is limited by carotid and aortic chemoreceptor mechanisms
As pO2 should be maintained

37
Q

What are other compensatory mechanisms for metabolic acidosis?

A

Decreased glomerular filtration of HCO3-

38
Q

What are other compensatory mechanisms for metabolic alkalosis?

A

Decreased renal H+ secretion

Reduced HCO3- reabsorption
If levels are very high HCO3- can be excreted in urine

39
Q

Why may compensation be complete or incomplete?

A

Compensatory mechanisms may not have time to form in severe acute disturbances

If acid-base disorder slowly develops = compensation will happen more effectively

Human Physiology Y3 (14 decks)

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