Chapter 15- Fluid and Acid-base balance Flashcards
(94 cards)
1
Q
What is balance concept?
A
Input must equal output to maintain a stable balance in ECF
2
Q
When does a positive balance exist?
A
When input exceeds output
3
Q
When does a negative balance exist?
A
When output exceeds input
4
Q
What is an example of input?
A
Ingestion
Metabolic consumption
5
Q
What is an example of output?
A
Excretion
metabolic consumption
6
Q
Why is input poorly controlled?
A
Eating habits are variable
7
Q
Where do compensatory adjustments occur?
A
usually on output side by urinary excretion
8
Q
What is the most abundant substance in the body?
A
Water
-Amount varies in different tissues
-Content remains fairly constant
9
Q
What percent of body fluid is extracellular?
A
33%
10
Q
what percent of body fluid is intracellular?
A
67%
11
Q
What is extracellular fluid made from?
A
interstitial fluid- 75%
Plasma- 25%
12
Q
What are the 2 major fluid compartments?
A
2/3 within the cells = ICF
1/3 in fluid surrounding the cells= ECF
13
Q
What are the minor components of ECF?
A
Lymph and transcellular fluid
14
Q
What is the barrier separating the ECF and ICF?
A
Cellular plasma membranes
15
Q
What does the ICF contain that can’t leave the cells?
A
Proteins
-cant permeate cell membrane
16
Q
Difference between ECF and ICF?
A
Unequal distribution of Na and K
17
Q
What does the ECF serve as?
A
Intermediary between the cells and external environment?
18
Q
What does kidney function do to ECF?
A
Regulates volume and osmolarity
19
Q
Why is ECF volume regulated?
A
maintains blood pressure
20
Q
What is important in long term regulation of ECF volume?
A
mainting salt NaCl balance
21
Q
Why is ECF osmolarity regulated?
A
Prevent swelling or shrinking of cells
22
Q
What is important in maiting ECF osmolarity?
A
Water balance
23
Q
How does salt input occur?
A
through ingestion
24
Q
How is salt balance maintained?
A
Outputs in urine
+lost in sweating and feces
25
How do the kidneys adjust the amount of salt excreted?
By controlling Glomerular filtration rate and Tubular reabsorption of sodium
26
What do deviations in ECF volume trigger?
Trigger renal compensatory responses that bring salt balance back into line
27
What is osmolarity?
Measure of the concentration of individual solute particles dissolved in a fluid
28
What do ECF and ICF have the same despite large chemical differences?
Same osmolarity
-no net movement of water
29
If fluid outside cell has same osmolarity?
isotonic
30
If fluid outside cell has higher osmolarity?
Hypertonic
31
If fluid outside cell has lower osmolarity?
Hypotonic
32
What accounts for the majority of the ECF's osmotic activity?
Sodium and its attendant anions
33
What accounts for the majority of ICF's osmotic activity?
Potassium and accompanying intracellular anions
34
What leads to changes in ECF osmolarity?
Circumstances that result in a loss or gain of free H2O
35
Examples of circumstances that alter ECF osmolarity?
1. Deficit of free water in ECF
2. Excess of free water in ECF
36
What is the osmolarity of when there is a water deficit?
Hypertonic
-too concentrated
-Dehydration
37
What is the osmolarity when there is a water excess?
Hypotonic
-too dilute
-overhydration
38
What happens to cells when they experience hypertonicity?
Cells shrink (ECF is too concentrated: water leaves cells)
39
What causes hypertonicity?
Insufficient water intake
Excessive water loss
Diabetes insipidus
40
What are the symptoms and effects of hypertonicity?
âš«Shrinking of brain neurons
-Confusion, irritability, delirium, convulsions, coma
âš« Circulatory disturbances
-Reduction in plasma volume, lowering of blood pressure, circulatory shock
âš« Dry skin, sunken eyeballs, dry tongue
41
What happens to cells that experience hypotonicity?
Cells swell
-excess water usually excreted in urine
42
What causes Hypotonicity?
Causes
âš« Patients with renal failure who cannot excrete a dilute urine become hypotonic when they consume more water than solutes
⚫ Can occur in healthy people when water is rapidly ingested and kidney’s do not respond quickly enough
âš« When excess water is retained in body due to inappropriate secretion of vasopressin
43
Hypotinicity symtoms and effects?
âš« Swelling of brain cells
-Confusion, irritability, lethargy, headache, dizziness,
vomiting, drowsiness, convulsions, coma, death
âš« Weakness (due to swelling of muscle cells)
âš« Circulatory disturbances (hypertension and edema)
âš« Excess free water = Water intoxication
44
How do you maintain stable water balance?
Water input must equal water output
45
What are the two types of output loss?
Insensible loss
Sensible loss
46
What is insensible loss?
Lungs, non-sweating skin
47
What is sensible loss?
Sweating, feces, urine excretion
-controlled to keep balance
48
Where is water excretion controlled in the kidney?
Collecting ducts and tubules of nephron
49
What controls water excretion?
Vasopressin
-restores ECF osmolarity
50
Where is vasopressin produced?
Hypothalamus
51
Where is vasopressin released?
Posterior pituitary gland
52
What is the hypothalamus the location of?
Thirst centre
53
What are hypothalamic osmoreceptors?
Sense changes in osmolarity
54
Where are hypothalamic osmoreceptors located?
Near vasopressin-secreting cells and thirst centre
55
If osmolarity increases what occurs via hypothalamic osmoreceptors?
Increased vasopressin and thirst is stimulated
56
If osmolarity decreases what occurs via hypothalamic osmoreceptors?
decreased vasopressin and thirst is suppressed
57
What else stimulates vasopressin secretion and thirst?
left atrial receptor (reduction in arterial pressure)
Angiotensin II (when RAAS is activated to conserve Na)
58
What does ECF fluid volume control?
Blood pressure
59
What does ECF fluid osmolarity control?
Cell volume: The shape of the cell
60
What is Acid-Base balance?
Precise regulation of free/unbound hydrogen concentration in ECF (body fluids)
61
What are acids?
Group of H containing substances that dissociate in solution to release free H and anions
62
What kind of acid has a greater tendency to dissociate in a solution?
Strong acids
63
What is a base?
Substance that can combine with free H and remove it from solution
64
What is pH?
A scale used to express the concentration of H+
65
What is acidosis?
When blood pH falls below a 7.35
-Becomes acidic
66
What is alkalosis?
When blood pH is above a 7.45
-Becomes basic
67
What are consequences related to fluctuations in pH?
a) changes in excitability of nerve and muscle cells
b) marked decrease of H causes over excitability of nervous
c) influences enzyme activity
d) changes K levels in body (affects cardiac functions)
68
What are some sources of H+ in the body?
1. Carbonic acid formation
2. Inorganic acids produced during breakdown of nutrients
3. organic acids from intermediary metabolism (fatty acids)
69
What are the body's lines of defence for pH changes?
1. Chemical buffer system
2. Respiratory system
3. Kidneys
70
What is the chemical buffer system?
Fist line of defence with four systems. Minimises changes of pH by binding with or yielding free H+
71
What are the four systems of the chemical buffer system?
1. H2CO3-, HCO3 System
2. Protein Buffer system
3. Hemoglobin (CO2) system
4. Phosphate system
72
What is theH2CO3-, HCO3 System?
Primary ECF buffer for non carbonic acids
73
What is carbonic acid?
Reaction of water with CO2
H2CO3
74
What are inorganic acids?
Acids produced during the breakdown of nutrients
e.g; H2SO4, phosphoric acids found in meats
75
What are organic acids?
acids resulting from intermediary metabolism
e.g; Fatty acids
76
What is the protein buffer system?
Primary ICF buffer, it also buffers ECF
77
What is Hemoglobin (CO2) system?
Primary buffer against carbonic acid changes
78
What is the phosphate system?
Important urinary buffer, also buffers ICF
79
What is the respiratory system's role in the Chemical buffer system?
Second line of defence
Acts at moderate speed, regulates pH by control rate of CO2 removal
80
What is the kidney's role in the Chemical Buffer system?
Third line of defence
Takes hours to days to compensate for changes adjusts
a. H+ excretion
b. HCO3- excretion
c. Ammonia secretion
81
What causes Acid-base imbalances?
Arise from either respiratory dysfunction or metabolic disturbances
82
What is respiratory acidosis ?
Blood pH falls below a 7.35 because of abnormal CO2 retention arising from hypoventilation
83
What are some possible causes of Hypoventilation ---> respiratory acidosis?
Lung disease
e.g; emphysema, bronchitis, asthma
Depression of respiratory centre by drugs/disease
nerve, muscle disorders reducing respiratory muscle activity
Holding breath
84
How does the body compensate for respiratory acidosis?
a. Chemical buffers immediately take uo additional H+
b.Kidneys conserve all filtered HCO3- and add new HCO3- to plasma, and excrete more H+
85
What compensation inmost important during respiratory acidosis?
Kidneys
86
What is respiratory alkalosis?
Blood pH rises above 7.45 primarily due to excessive loss of CO2 from body as a result of Hyperventilation
-its a loss of H+ and HCO3-
87
What causes respiratory alkalosis?
Fever
Anxiety/other stressors
Aspirin poisoning
Physiologic mechanisms at high altitudes
88
How does the body compensate for respiratory alkalosis?
a. Chemical buffer systems liberate H+
b. After a few days if it continues, kidneys conserve H+ and excrete more HCO3-
89
What is metabolic acidosis?
Blood pH falls below a 7.35 due to any type of acidosis except those caused by excess CO2 in body fluids
Its a reduction in plasma HCO3 or accumulation of non-carbonic acids
90
What causes metabolic acidosis?
-Severe diarrhoea
-Diabetes mellitus
-Strenuous exercise
-Uremic acidosis
91
How does the body compensate for metabolic acidosis?
a. Buffers take up extra H+
b.Lungs blow off additional H+ generating CO2
c.Kidneys excrete more H+ and conserve more HCO3
92
What is metabolic alkalosis?
Blood pH rises above a 7.45 due to a reduction in plasma H+ caused by relative deficiency of non-carbonic acids
93
What causes metabolic alkalosis?
-Vomiting
-Ingestion of alkaline drugs
94
How does the body compensate for metabolic alkalosis?
a. Chemical buffers immediately liberate H+
b. Ventilation reduces
c.If condition persists, kidneys conserve H+ and excrete excess HCO3- in urine
