Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Genitourinary MBCHB2 > Lecture 7: Acid Base Balance 1 > Flashcards

Lecture 7: Acid Base Balance 1 Flashcards

1
Q

What is a strong vs weak acid:

A
  • A strong acid is an acid that completely dissociates in solution i.e the [H+] equals the intial acid concentration. i.e fully ionised HCL-> H+ and Cl-
  • A weak acid is an acid that only partially dissociates in solution i.e H2CO3-> H+ and HCO3 (only a small amount of carbonic acid exists as H+ in solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe pH in normal homeostasis

A

7.35-7.45 for cellular and enzyme function (tightly controlled)

This corresponds to a [H+] ranging from 35-45nMol/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why do we need acid base regulation?

A

Humans are net producers of acids:

  • Volatile i.e CO2
  • Non-volatile i.e from metabolism of dietary protein etc

Thus need to protect homeostasis or pH changes could be very bad

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is acidaemia and alkalaemia?

A 
Acidaemia = pH\<7.35 
Alkalaemia = pH\>7.45
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Write some notes on acidosis:

A

pH < 7.35

  • pH < 7.2 = severe acidosis
  • pH < 6.9 = Usually incompatible with life
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Write some notes on alkalosis

A

pH < 7.45

  • pH < 7.6 = severe alkalosis
  • pH < 7.9 = Usually incompatible with life
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the components of acid base balance?.

A
  • Diet
  • Blood
  • Liver
  • Lungs
  • Kidneys

i.e Many facets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the three mechanisms in which the body prevents dangerous changes in pH?

A
  1. Buffers
  2. Respiratory control of ventilation
  3. Excretion of acids (or bases) by the kidneys

** Every change of 0.3pH represents a change in [H+] by a factor of 2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a buffer?

A

Buffers are a solution consisting of a weak acid and its conjugate base

  • A buffer is a chemical in solution that resits changes in pH i.e mopping up H+
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does a buffer work?

A
  1. H+ is added, increasing H+ and lowering pH
  2. Equilibrium is right shifted
  3. H+ are consumed by the buffer conjugate base/anion, forming the buffer conjugate weak acid
  4. [H+] reduces, restoring pH to(wards) normal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the four buffers of blood?

A

Bicarbonate
Haemoglobin
Phosphate
Proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe how bicarbonate acts as a buffer:

A

H+ (+) HCO3- H2CO3 H2O (+) CO2

  • Carbonic acid only exists in very small amounts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe how Hb acts as a buffer:

A

Hb

  • Dissolved CO2 enters RBC, some binds Hb
  • Rest becomes HCO3 and H, the H produced is buffered by the Hb whilst HCO3 diffuses into the plasma in exchange for chloride
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe how phosphate acts as a buffer

A

H + HPO4 H2PO4

Both phosphate and proteins contribute relatively little to buffering by blood and ECF due to their relatively low concentrations in plasma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe how proteins act as a buffer:

A

H + i.e albumin HA

Both phosphate and proteins contribute relatively little to buffering by blood and ECF due to their relatively low concentrations in plasma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are other buffers aside from the ones in blood and ECF?

A

Muscle + liver (H+Cl enter cell and exchanged for cation)
Bone (Usually only in chronic acidosis, but CaCO3 accepts H+ and forms Ca and HCO3)

17
Q

What equation determines the pH

A

Henderson-hasselbach equation

pH = 6.74 + log (HCO3/CO2)

18
Q

Describe the contribution of respiration to acid-base regulation

A
  • CO2 is removed via ventilation
  • Oxidative metabolism produces CO2 which forms HCO3 + H in the blood.
  • Low pH stimulates ventilation
  • Increased ventilation blows off CO2

Increased pCO2 causes acidosis
Decreased pCO2 causes alkalosis

19
Q

Describe the role of the kidneys in acid- base balance

A

Metabolism produces H+ and these are excreted into the kidney to balance non-volatile acid generated through metabolism

Excess H is buffered by:

  • > Phosphate buffers
  • > Ammonia buffers
20
Q

What are the two main renal processes in acid-base balance

A
  1. Reabsorption of filtered bicarbonate (includes generation of ‘new’ bicarbonate
  2. H+ Secretion in distal nephron (DT and CD), principally via ammonia, phosphate

Refer to previous lecture for detailed notes // explain this here

21
Q

Describe the response of the kidney to an acid load:

A
  • Increased HCO3 and H+ transport along the nephron
  • Increased ammoniogenesis
  • Increased availability of urinary buffers (mainly via ammonia)
22
Q

What is the mantra of acid base physiology

A

Acidity = Bicarbonate / Carbon Dioxide

23
Q

What happens with respiratory disturbance in acid/base:

A

Respiratory acidosis = CO2 retention

Respiratory alkalosis = Hyperventilation

24
Q

What happens in metabolic disturbances acid base physiology

A

Metabolic acidosis: Increased acid production (low pH) (Low HCO3 as it buffers it)

Metabolic alkalosis: Loss of acid due to vomiting (stomach acid = HCl) (high pH and high HCO3 (from CO2, limitless supply))

25
Q

If the disorder is respiratory where does compensation occur?

A
  • Compensation is by the kidneys
  • This takes days
26
Q

If the disorder is metabolic where does compensation occur?

A
  • Compensation is by the lungs (+/- kidneys)
  • This takes hours

ECF buffering corresponds to the HCO3 bicarb buffer system

27
Q

Describe the compensation for respiratory disorders:

A

Ventilatory failure -> Inc. pCO2 -> Dec. pH -> Inc. H+ secretion and NH3 synthesis (Inc. HCO3)

Results in: Acid excretion as NH4

NB: Immediate effect of buffers has been omitted as these would have already occurred

(Process reversed for metabolic alkalosis)

28
Q

Describe compensation for (non-renal) metabolic disorders:

A

H+ accumulation via addition of acid or loss of HCO3 (i.e from gut)

Decreased pH, (HCO3 buffers and blunts this) this results in:

-> Inc. ventilation, decreasing pCO2 (develops over hours)

–> Renal compensation develops over days (inc. H+ secretion, inc NH3 secretion = acid excretion as NH4)

= pH return towards normal

(Process reversed for metabolic alkalosis)

29
Q

Describe compensation for renal metabolic disorders

A

Loss of HCO3 from kidneys results in H+ accumulation

Decreased pH (HCO3 buffers and blunts this)
=
Increased ventilation (dec. pCO2), pH returns towards normal

RENAL COMPENSATION LIKELY ABSENT FOR RENAL METABOLIC DISORDERS

(Process reversed for metabolic alkalosis)

30
Q

What is it called be low pH stimulates breathing?

A

Acidotic breathing

31
Q

In metabolic acidosis, how does the respiratory compensation function?

A

Reduction in pCO2 (hours)

Restores the pCO2/HCO3 ratio

32
Q

In respiratory acidosis, how does the renal compensation function?

A

Increase in bicarbonate (days)

Restores the pCO2/HCO3 ratio

33
Q

Summarise the changes in HCO3 and pCO2 in:

  • Metabolic alkalosis
  • Acute respiratory acidosis
  • Acute respiratory alkalosis
  • Metabolic acidosis
  • Mixed resp and metabolic acidosis
A
34
Q

Describe the compensation and pH changes of:

Metabolic acidosis
Resp. alkalosis
Resp. acidosis
Metabolic alkalosis

A

Genitourinary MBCHB2 (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions