Lecture 11 pt 1: Acid-base balance

Question 1

1) What does acid base balance refer to?
2) Define acids
3) Stronger acid = _______________ tendency to dissociate. How is this expressed?

Answer 1

1) Precise regulation of unbound hydrogen ions (H+)
2) Substances that dissociate from H+ when in solution
3) greater; dissociation constant

Question 2

True or false: Many other non-acids (like carbs) contain hydrogen but do not dissociate

Answer 2

True

Question 3

1) What is a base?
2) What binds H+ more readily, a strong base or weak base?

Answer 3

1) Substance that can combine with free H+, removing it from solution
2) Strong base

Question 4

1) Concentration of H+ in normal ECF is _______________ times lower than Na+
2) Due to such low values, how is this expressed?
3) Higher acidity (higher H+) = _________ pH
4) Every unit change in pH represents a _____-fold change in H+

Answer 4

1) 3 million
2) Logarithmically as pH
3) lower
4) 10-fold

Question 5

1) pH of 7 has _____ times fewer H+ than pH of 6
2) pH of H2O is what?

Answer 5

1) ten
2) 7.0 (considered to be neutral)

Question 6

1) What does a pH lower than 7 indicate?
2) What does a pH higher than 7 indicate?

Answer 6

1) More H+ = acidic
2) Less H+ = alkaline/basic

Question 7

1) What is a normal blood pH?
2) What is arterial blood pH? What about venous?

Answer 7

1) pH normally around 7.4 (slightly basic)
2) Arterial 7.45, venous 7.35 (carbonic acid/CO2)

Question 8

1) Define acidosis and when it becomes lethal
2) Define alkalosis and when it becomes lethal

Answer 8

1) Blood pH below 7.35; pH 6.8 lethal in seconds
2) Blood pH above 7.45; pH 8.0 lethal in seconds

Question 9

Small changes in __[ion]___ can have dramatic consequences

Answer 9

H+

Question 10

1) What does increased H+ do to the CNS?
2) What does decreased H+ do to the CNS?
3) H+ deviations can affect the shape of what? What does this disturb?

Answer 10

1) Depresses CNS
2) Increases CNS excitability (twitches, spasms, convulsions, death)
3) Proteins; metabolic activity of enzymes

Question 11

1) How is K+ balance kept?
2) What can affect it and what does this lead to?

Answer 11

1) Renal tubular cells secrete (extrude) K+ or H+ to reabsorb Na+
2) H+ abnormalities can affect K+ concentrations leading to cardiac abnormalities

Question 12

Normally there is much more K+ than H+, but if there is ____________ (increased H+) body will compensate by secreting H+ instead (or opposite effect if in ___________)

Answer 12

acidosis (increased H+); alkalosis

Question 13

True or false: As with any other constituent, input of H+ must be balanced with output

Answer 13

True

Question 14

1) What is the main input of H+?
2) What is the primary source of this main input of H+?

Answer 14

1) Main input is metabolic activity, very minimally affected by ingestion
2) Carbonic acid formation is main source

Question 15

List and describe the 3 ways metabolic activity produces H+

Answer 15

1) Carbonic acid formation (main source)
-Metabolically produced CO2 combines with water to form carbonic acid (H2CO3) which dissociates to form H+ and bicarb (HCO3)
2) Inorganic acids during nutrient breakdown
3) Organic acids during metabolic activities (fatty acids, lactic acid)

Question 16

What are the 3 lines of defense against changes in H+?

Answer 16

1) Chemical buffers
2) Respiratory pH control
3) Renal pH control

Question 17

1) Define chemical buffers
2) What is the most common example of this?
3) Give an example

Answer 17

1) Dissolved compounds that minimize pH changes in either direction
2) Pair of substances in a reversible reaction, one substance can bind to H+ and the other can yield it.
3) H2CO3 (carbonic acid) with H+/HCO3 (bicarbonate)

Question 18

The body has four chemical buffer systems, what are they?

Answer 18

1) H2CO3/HCO3
2) Protein buffer system
3) Hgb buffer system
4) Phosphate buffer system

Question 19

1) What is the most important pH buffer in ECF?
2) Why?
3) How is each component of this buffer regulated?

Answer 19

1) H2CO3/HCO3 Buffer
2) Abundant in ECF, readily available to resist pH changes
3) Each closely regulated: Kidneys regulate HCO3, lungs regulate CO2

Question 20

1) What buffer system is primarily important in ICF?
2) What does it contain? What can these do?
3) What makes them the most important buffer in the ICF?

Answer 20

1) Protein buffer system
2) Contain both acidic and basic groups that can donate or accept H+
3) Sheer abundance

Question 21

Hemoglobin buffers _____ from metabolically produced ____ between tissues and lungs

Answer 21

H+; CO2

(HGB buffer)

Question 22

1) What happens to most H+ generated from CO2 at tissue level? Why?
2) Because of the Hgb buffer, venous blood is only slightly more __________ than arterial blood

Answer 22

1) Becomes bound to Hgb, otherwise blood at the tissues would be too acidic
2) acidic

Question 23

1) What is the phosphate buffer?
2) Is this reversible?
3) Describe its abundance in the ECF
4) Describe its abundance in the ICF
5) Where is this buffer useful?

Answer 23

1) Acid phosphate salt (NaH2PO4) can donate H+ and basic phosphate salt (Na2HPO4) can accept H+
2) Reversible reaction
3) ECF concentration is low
4) Not as abundant as proteins in ICF
5) Excellent urinary buffer

Question 24

1) Why is phosphate a good urinary buffer?
2) When does it buffer urine?

Answer 24

1) Humans consume more phosphate than needed
2) During formation

Question 25

Resp. control of pH:
1) Altering pulmonary ventilation alters excretion of what?
2) CO2 is not an _______, it combines with H2O to form ___________ which then dissociates into H+ and ________.

Answer 25

1) H+ generating CO2
2) acid; carbonic acid; bicarb

Question 26

Resp control of pH:
1) Metabolically generated CO2 can increase what?
2) What does this trigger and why?
3) What effect does this have?

Answer 26

1) Arterial H+
2) Respiratory reflex in brain stem, to increase pulmonary ventilation
3) Increase CO2 exchange

Question 27

Resp. control of pH:
1) If metabolically generated CO2 is low, what happens to respiration?
2) Metabolic _________ increases pulmonary ventilation
3) Metabolic _________ decreases pulmonary ventilation

Answer 27

1) Ventilation reduces
2) acidosis
3) alkalosis

Question 28

Renal pH control:
Kidneys regulate pH by adjusting what 3 things?

Answer 28

1) H+ excretion
2) Bicarb (HCO3) excretion
3) Ammonia (NH3) excretion

Question 29

1) What do the lungs eliminate? What eliminates the H+ specifically?
2) List 2 acids the kidneys remove

Answer 29

1) Lungs only eliminate the CO2, the generated H+ must also be removed by kidneys
2) Lactic and phosphoric acid

Question 30

Deviations from normal acid-base levels are divided into four categories based on source and direction of H+ change; what are they?

What characterizes each?

Answer 30

1+2) Respiratory acidosis/alkalosis
-Increased/decreased CO2
3+4) Metabolic acidosis/alkalosis
-Decreased/increased HCO3

Question 31

Aren’t CO2 and HCO3 interchangeable? Explain

Answer 31

No:
Although CO2 combines with H2O to eventually form HCO3 and H+, the concentration of HCO3 is 600,000 times that of H+.
An increase in CO2 will bring about a profound change in H+ but not necessarily HCO3. These are separate.

Question 32

1) Abnormally increased CO2 (respiratory acidosis) arises from what?
2) What can cause this?

Answer 32

1) Hypoventilation
2) Lung disease, neuromuscular disease, drugs, holding breath (transient)

Question 33

What are the 2 compensatory mechanisms for respiratory acidosis?

Answer 33

1) Chemical buffers take up additional H+.
2) Kidneys: most important. Retains HCO3- and adds it to plasma, also increase H+ secretion

Question 34

1) Abnormally decreased CO2 (respiratory alkalosis) arises from what?
2) What can cause this?

Answer 34

1) Hyperventilation
2) Fever, anxiety, aspirin poisoning, high altitude

Question 35

What are the 2 compensatory mechanisms for respiratory alkalosis?

Answer 35

1) Chemical buffers liberate H+ to diminish alkalosis.
2) Kidneys conserve H+ excretion, increase HCO3- secretion.

Question 36

1) What is metabolic acidosis?
2) What can cause it?

Answer 36

1) Abnormally decreased HCO3-
2) Severe diarrhea, diabetes, strenuous exercise, severe renal failure (in which case renal mechanism cannot compensate)

Question 37

What are the 3 compensatory mechanisms for metabolic acidosis?

Answer 37

1) Buffers take up extra H+
2) Pulmonary ventilation increases (blowing off additional CO2)
3) Kidneys excrete more H+, conserve HCO3-

Question 38

1) What is metabolic alkalosis?
2) What can cause it?

Answer 38

1) Abnormally increased HCO3-
2) Vomiting, alkaline drugs

Question 39

What are the 3 compensatory mechanisms for metabolic alkalosis?

Answer 39

1) Buffers liberate H+
2) Ventilation decreased (less CO2 blown off)
3) Kidneys conserve H+, increase HCO3- excretion

Question 40

What ion do the kidneys regulate?

Answer 40

Bicarbonate

Question 41

Describe pH, CO2, and HCO3- in:
uncompensated respiratory acidosis

Answer 41

Decreased pH, increased CO2, normal HCO3-

Question 42

1) How do people breathe to compensate for respiratory acidosis?
2) What molecule is abundant?
3) When is bicarb elevated?

Answer 42

1) Rapidly and shallowly
2) CO2
3) When our bodies start retaining bicarb

Question 43

Describe pH, CO2, and HCO3- in uncompensated metabolic acidosis

Answer 43

Decreased pH, normal CO2, decreased HCO3-

Question 44

Describe pH, CO2, and HCO3- in uncompensated metabolic alkalosis

Answer 44

Increased pH, normal CO2, increased HCO3-