Lecture 39 Flashcards

1
Q

pH definition

A

Partial pressure of H+ in solution

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2
Q

Types of buffers in the body

A

Chemical

  • proteins
  • bicarbonate
  • ammonia

Physiological
- excretion of acids or bases in the renal system

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3
Q

Renal system use of buffer system

A

Uses both physiological and chemical processes to regulate blood pH levels
Using HCO3- and H+

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4
Q

Process of buffering of H+ ions into the nephron for excretion

A
HCO3- forms with H+
Dissociates to form H2O and CO2 
Diffuses into the tubular cells 
Reforms to H2CO3 using carbonic anhydrase 
Dissociates into HCO3- and H+
H+ enters the filtrate

Process begins again

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5
Q

Renal correction of acidosis

A

As pH drops, HCO3- is taken up by the kidneys
Secretion of H+ causes excretion of surplus H+ ions
CO2 converted to HCO3-, making the ECF more alkaline (uptake of H+ ions)

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6
Q

What happens when pH is below 4.5 in filtrate

A

No more H+ ions will be secreted into the nephron
Limits control of pH limiting by HCO3-
NH3 takes up additional H+
Forming NH4+
NH4+ cannot be reabsorbed
Additional H+ will be excreted in form of NH4+

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7
Q

Where does NH3 come from?

A

Protein metabolism

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8
Q

How to make acidic urine in mild acidosis?

A

HCO3- forms with H+ ions
Making H2CO3
Absorbed into tubular cells in form of CO2 and H2O
Reforms H2CO3 in tubular cells
HCO3- formed diffuses into blood = alkaline effect
H+ excreted

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9
Q

Acidic urine in severe acidosis?

ECF v acidic

A

NH3 diffuses into tubular lumen combining with H+

NH4+ excreted in urine

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10
Q

Acidosis symptoms

A
Cardiovascular dysfunction 
Confusion
CNS depression 
Seizures 
Coma if below pH7
Excitable cells of the body harder to stimulate due to CNS depression
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11
Q

Why does acidosis lead to CNS depression and cardiovascular dysfunction?

A

Plasma proteins less ionised, (more H+ binding to the plasma proteins) less calcium taken up by them
More free calcium blocks Na+ channels
Causing depolarisation of neurones and myocytes harder
Lack of nerve or cardiac action potentials cause coma and cardiac arrest

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12
Q

Causes of acidosis

A

Respiratory acidosis

Metabolic acidosis

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13
Q

Respiratory acidosis causes and what we’d see

A

Ventilatory failure
Complications of COPD or Asthma

See 
↓ PaO2
↑ PaCO2 
Slightly low pH 
Raised plasma HCO3- due to renal compensation
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14
Q

Renal injury/disease causing metabolic acidosis

A

Cause ↓ HCO3- reabsorption

↓ H+ secretion and excretion

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15
Q

Diarrhoea causing metabolic acidosis

A

More Na+ in filtrate means ↓ H+ secreted
Less HCO3- reabsorbed
Acidosis

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16
Q

Diabetes mellitus causing acidosis

A

Ketoacidosis caused by metabolism of fats

17
Q

Alcoholism causing acidosis

A

Kidney damage due to inflammation. Oxidative stress and hypertension

18
Q

Addisons disease causing acidosis

A

↓ aldosterone = ↓ sodium / hydrogen pump -↓ hco3 reabsorbtion

19
Q

What we expect to see in the blood in acidosis

A

↓ pH

↓ HCO3- concentration

20
Q

Renal correction of alkalosis

A

↓ in H+ secretion due to the ↓ HCO3- reabsorbtion into ECF
HCO3- will be excreted in the urine
Body constantly producing more H+ ions= ↓ pH = resolved alkalosis

21
Q

Definition of uncompensated alkalosis

Symptoms

A
<7.45pH 
Confusion
Spontaneous muscle spasm 
Tetany 
Respiratory paralysis
22
Q

Why does alkalosis cause these symptoms

A

↑ excitability of cells due to plasma proteins being more ionised (binds less H+ ions)
↑ calcium binding ↓ ECF CALCIUM
↑ membrane permeability to Na+
Easier to form an AP

23
Q

Causes of respiratory alkalosis

A

Hyperventilation
↓ PaCO2 ↓ HCO3- due to renal compensation
Alkaline blood
HCO3- excreted in the urine to ↑ H+ concentration

24
Q

Bicarbonate overdose causing alkalosis

A

↑ HCO3- ↑ PaCO2 (Due to respiratory compensation)

↑ HCO3- = ↓ H+ = alkalosis

25
Q

Hyperaldosteronism causing alkalosis

A

↑ in the secretion of H+ due to Na+/H+ pump governed by aldosterone
↑ excretion of H+

26
Q

Vomiting causing Alkalosis

A

↓ gastric acid