Lecture 11 pt 1: Acid-base balance Flashcards
1) What does acid base balance refer to?
2) Define acids
3) Stronger acid = _______________ tendency to dissociate. How is this expressed?
1) Precise regulation of unbound hydrogen ions (H+)
2) Substances that dissociate from H+ when in solution
3) greater; dissociation constant
True or false: Many other non-acids (like carbs) contain hydrogen but do not dissociate
True
1) What is a base?
2) What binds H+ more readily, a strong base or weak base?
1) Substance that can combine with free H+, removing it from solution
2) Strong base
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+
1) 3 million
2) Logarithmically as pH
3) lower
4) 10-fold
1) pH of 7 has _____ times fewer H+ than pH of 6
2) pH of H2O is what?
1) ten
2) 7.0 (considered to be neutral)
1) What does a pH lower than 7 indicate?
2) What does a pH higher than 7 indicate?
1) More H+ = acidic
2) Less H+ = alkaline/basic
1) What is a normal blood pH?
2) What is arterial blood pH? What about venous?
1) pH normally around 7.4 (slightly basic)
2) Arterial 7.45, venous 7.35 (carbonic acid/CO2)
1) Define acidosis and when it becomes lethal
2) Define alkalosis and when it becomes lethal
1) Blood pH below 7.35; pH 6.8 lethal in seconds
2) Blood pH above 7.45; pH 8.0 lethal in seconds
Small changes in __[ion]___ can have dramatic consequences
H+
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?
1) Depresses CNS
2) Increases CNS excitability (twitches, spasms, convulsions, death)
3) Proteins; metabolic activity of enzymes
1) How is K+ balance kept?
2) What can affect it and what does this lead to?
1) Renal tubular cells secrete (extrude) K+ or H+ to reabsorb Na+
2) H+ abnormalities can affect K+ concentrations leading to cardiac abnormalities
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 ___________)
acidosis (increased H+); alkalosis
True or false: As with any other constituent, input of H+ must be balanced with output
True
1) What is the main input of H+?
2) What is the primary source of this main input of H+?
1) Main input is metabolic activity, very minimally affected by ingestion
2) Carbonic acid formation is main source
List and describe the 3 ways metabolic activity produces H+
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)
What are the 3 lines of defense against changes in H+?
1) Chemical buffers
2) Respiratory pH control
3) Renal pH control
1) Define chemical buffers
2) What is the most common example of this?
3) Give an example
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)
The body has four chemical buffer systems, what are they?
1) H2CO3/HCO3
2) Protein buffer system
3) Hgb buffer system
4) Phosphate buffer system
1) What is the most important pH buffer in ECF?
2) Why?
3) How is each component of this buffer regulated?
1) H2CO3/HCO3 Buffer
2) Abundant in ECF, readily available to resist pH changes
3) Each closely regulated: Kidneys regulate HCO3, lungs regulate CO2
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?
1) Protein buffer system
2) Contain both acidic and basic groups that can donate or accept H+
3) Sheer abundance
Hemoglobin buffers _____ from metabolically produced ____ between tissues and lungs
H+; CO2
(HGB buffer)
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
1) Becomes bound to Hgb, otherwise blood at the tissues would be too acidic
2) acidic
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?
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
1) Why is phosphate a good urinary buffer?
2) When does it buffer urine?
1) Humans consume more phosphate than needed
2) During formation
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 ________.
1) H+ generating CO2
2) acid; carbonic acid; bicarb
Resp control of pH:
1) Metabolically generated CO2 can increase what?
2) What does this trigger and why?
3) What effect does this have?
1) Arterial H+
2) Respiratory reflex in brain stem, to increase pulmonary ventilation
3) Increase CO2 exchange
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
1) Ventilation reduces
2) acidosis
3) alkalosis
Renal pH control:
Kidneys regulate pH by adjusting what 3 things?
1) H+ excretion
2) Bicarb (HCO3) excretion
3) Ammonia (NH3) excretion
1) What do the lungs eliminate? What eliminates the H+ specifically?
2) List 2 acids the kidneys remove
1) Lungs only eliminate the CO2, the generated H+ must also be removed by kidneys
2) Lactic and phosphoric acid
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?
1+2) Respiratory acidosis/alkalosis
-Increased/decreased CO2
3+4) Metabolic acidosis/alkalosis
-Decreased/increased HCO3
Aren’t CO2 and HCO3 interchangeable? Explain
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.
1) Abnormally increased CO2 (respiratory acidosis) arises from what?
2) What can cause this?
1) Hypoventilation
2) Lung disease, neuromuscular disease, drugs, holding breath (transient)
What are the 2 compensatory mechanisms for respiratory acidosis?
1) Chemical buffers take up additional H+.
2) Kidneys: most important. Retains HCO3- and adds it to plasma, also increase H+ secretion
1) Abnormally decreased CO2 (respiratory alkalosis) arises from what?
2) What can cause this?
1) Hyperventilation
2) Fever, anxiety, aspirin poisoning, high altitude
What are the 2 compensatory mechanisms for respiratory alkalosis?
1) Chemical buffers liberate H+ to diminish alkalosis.
2) Kidneys conserve H+ excretion, increase HCO3- secretion.
1) What is metabolic acidosis?
2) What can cause it?
1) Abnormally decreased HCO3-
2) Severe diarrhea, diabetes, strenuous exercise, severe renal failure (in which case renal mechanism cannot compensate)
What are the 3 compensatory mechanisms for metabolic acidosis?
1) Buffers take up extra H+
2) Pulmonary ventilation increases (blowing off additional CO2)
3) Kidneys excrete more H+, conserve HCO3-
1) What is metabolic alkalosis?
2) What can cause it?
1) Abnormally increased HCO3-
2) Vomiting, alkaline drugs
What are the 3 compensatory mechanisms for metabolic alkalosis?
1) Buffers liberate H+
2) Ventilation decreased (less CO2 blown off)
3) Kidneys conserve H+, increase HCO3- excretion
What ion do the kidneys regulate?
Bicarbonate
Describe pH, CO2, and HCO3- in:
uncompensated respiratory acidosis
Decreased pH, increased CO2, normal HCO3-
1) How do people breathe to compensate for respiratory acidosis?
2) What molecule is abundant?
3) When is bicarb elevated?
1) Rapidly and shallowly
2) CO2
3) When our bodies start retaining bicarb
Describe pH, CO2, and HCO3- in uncompensated metabolic acidosis
Decreased pH, normal CO2, decreased HCO3-
Describe pH, CO2, and HCO3- in uncompensated metabolic alkalosis
Increased pH, normal CO2, increased HCO3-
