Acid-Base Balance Flashcards
(50 cards)
1
Q
pH
A
- measurement of a solutions H+ concentration
2
Q
Normal pH of the body
A
- 4
- slightly alkaline
3
Q
1 pH unit = ?
A
a 10-fold change in H+ concentration
4
Q
pH changes can _______ proteins… why?
A
denature
- intracellular proteins are sensitive to pH changes
5
Q
Changes in [H+] results in..?
A
- disruptions in hydrogen bonds
- alters the structure
6
Q
Acidosis
A
- caused by a very low pH (excess H+)
- CNS depression, confusion, coma
7
Q
Alkalosis
A
- caused by a high pH (low H+)
- hyper excitability in sensory neurons and muscles
- sustained respiratory muscle contraction
8
Q
Acid Input
A
- result of diet and acids produced during metabolism
9
Q
Largest daily source of acid?
A
CO2 from aerobic metabolism
10
Q
pH Homeostasis Mechanisms
A
- buffers (first lie of defence)
- ventilations (handles 75% of
disturbances) - renal regulation of H+ and HCO3- (slowest)
11
Q
Buffer Systems
A
- includes proteins, phosphate ions, HCO3-
12
Q
Buffer Molecule
A
- moderates, but doesn’t prevent changes in pH by combining with or releasing H+
13
Q
No buffer
A
- adding acid to a solution causes a sharp change in pH
14
Q
Solution + Buffer
A
- H+ added is bound and pH change is slightly moderated or unnoticeable
15
Q
HCO3-
A
- large amounts present
- the most important extracellular buffer system
- can buffer H+ from non-respiratory sources
16
Q
Plasma [HCO3-]
A
- approx. 600,000x concentrated as plasma H+ (bound to Hb)
17
Q
Relationship Btwn CO2, HCO3-, H+ in Plasma
A
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
18
Q
Law of Mass Action
A
- any change in amount of CO2, HCO3-, H+ in solution causes reaction shift until new equilibrium is reached
19
Q
Increase in CO2
A
- shifts equation to right creating 1 H+ and 1 HCO3-
20
Q
Adding H+
A
- added through metabolic source (latic acid)
- shifts equation to the left
- HCO3- acts as a buffer
21
Q
How does ventilation compensate for pH disturbances?
A
- peripheral and central chemoreceptors sense changes in plasma PCO2 and/or H+ and signals to respiratory control centre to adjust ventilation accordingly
- can correct disturbances or cause them
22
Q
Hypoventilation
A
- right shift
- increase CO2 so increase in H+ and HCO3-
23
Q
Hperventilation
A
- left shift
- decrease CO2 so decrease in H+ and HCO3-
24
Q
What kind of buffers do the kidneys use?
A
ammonia and phosphate buffers
25
kidneys handle the remaining ____ of pH disturbances through two mechanisms:
25%
| mechanisms: Directly and Indirectly
26
Directly
- by altering the rates of excretion of reabsorption of H+
27
Indirectly
- by changing the rate at which HCO3- .buffer is reabsorbed or excreted
28
Ammonia Buffer
- within tubule cells
29
Phosphate Buffer
- in the lumen of kidneys
30
What happens to excess H+ during Acidosis?
- excess H+ is buffered by ammonia within tubule cells or enters lumen and is buffered by phosphate ions
31
H+ is not _____, enters _____ via _____ only.
1. filtered
2. tubule
3. secretion
32
Proximal Tubule
- secretes H+ and reabsorbs HCO3-
33
_____ amounts of HCO3- filtered
- high amounts
34
How is HCO3- filtered?
- indirectly because no apical transporter
35
Process of Proximal Tubule
1. NHE secretes H+
2. H+ in filtrate combines with filtered HCO3- to form CO2
3. CO2 diffuses into cell
4. CO2 combines with water to form H+ and HCO3-
5. H+ is secreted again
6. HCO3- is reabsorbed with Na+
7. Glutamine is metabolized to ammonium ion and HCO3-
8. NH4+ is secreted and excreted
36
Role of the Distal Nephron
- controls acid excretion
37
Role of the Collecting Duct
- plays a significant role in the fine regulation of acid-base balance
38
Type A Intercalated Cells
- acidosis
- function to increase H+ secretion and HCO3- reabsorption
- usually accompanied by increase K+ reabsorption (hyperkalemia)
39
Type B Intercalated Cells
- alkalosis
- function to increase H+ reabsorption and HCO3- secretion
- usually accompanied by increase K+ secretion (hypokalemia)
40
Three Compensatory Mechanisms
1. buffers
2. ventilation
3. renal excretion
- take care of most variations in plasma pH
41
Acid-Base Disturbances
- classified by direction of pH change and by underlying cause
42
Underlying Causes of Acid-Base Disturbances
1. metabolic
| 2. respiratory
43
Changes in Plasma pH due to Acid-Base Disturbances
- body buffers are ineffective at this point
| - respiratory and renal compensation alleviate the change in pH
44
Respiratory induced changes in pH must be resolved via ______ mechanisms
RENAL
| - excrete H+ and reabsorb HCO3-
45
Respiratory Acidosis
- occurs when alveolar hypoventilation results in CO2 retention and elevated plasma CO2
- pulmonary fibrosis and skeletal muscle disorders (muscular dystrophy)
46
Respiratory Alkalosis
- less common
- occurs as a result of hyperventilation in the absence of increased metabolic CO2 production
- in clinic: caused by excessive artificial respiration
- physiological: anxiety induced hyperventilation
- compensation: renal HCO3- excretion, H+ reabsorption
47
Metabolic Acidosis
- occurs when dietary and metabolic input of H+ exceeds H+ excretion
- lactic acidosis (anaerobic metabolism)
- ketoacidosis (excessive breakdown of fats and some amino acids)
- can also occur from excessive HCO3- loss (diarrhea)
48
Metabolic Acidosis Solution
- resolved by respiratory (increased ventilation) and slow renal compensation (HCO3- reabsorbed, H+ excreted)
49
Metabolic Alkalosis Causes
1. excessive vomiting of acidic stomach contents
| 2. excessive ingestion of bicarbonate-containing antacids
50
Metabolic Alkalosis Solutions
- usually resolved rapidly by a decrease in ventilation, but effectiveness is limited because it can because hypoxia
- renal response: HCO3- excreted, H+ reabsorbed
