Acid-Base regulation Flashcards
What is acid - base regulation?
Regulation of free H+ ion concentration in body fluids.
What are strong acids?
Strong acids = Greater percentage of molecules separate into free H+ ions e.g. Hydrochloric acid (HCl).
What are weak acids?
Weak acids = Greater percentage of molecules that remains intact. e.g. Carbonic Acid (H2CO3)
What is dissociation constant and what is the formula?
Dissociation Constant is measure of separation of H+ ion. Formula:
K= [H+] [HCO3-] /[H2CO3]
What is a base?
A base bind to H+ ions to remove them from the solution.
Strong bases react more readily
What is the formula for pH?
pH=log 1/[H+]
What is the neutral pH?
Neutral pH = 7
What is the acidic pH range?
Acid pH < 7 ( Low pH) - pH 1-6
What is the basic pH range?
Bases pH >7 (high pH) - pH 8-14
What is the pH for arterial blood?
pH Arterial blood = 7.45
What is the pH for venous blood?
pH venous blood = 7.35
What is acidosis?
Acidosis: Blood pH <7.35. This is when a high level of acid is in the body, which causes an imbalance in the body’s pH.
What is alkalosis?
Alkalosis: Blood pH >7.45. This is when your body and body fluids contain an excess of alkali. Occurs when your blood pH are imbalanced.
At what pH will death result?
Death will result outside pH 6.8 - 8.0 for more than a few seconds.
What happens to the nerve and muscle excitability when there is an increase in H+?
Increased H+ depresses CNS to produce disorientation and coma.
What happens to the nerve and muscle excitability when there is an decrease in H+?
Decreased H+ excites CNS to produce action potential generation - pins and needle sensation, twitches, spasms, convulsions, and death through respiratory failure.
What happens to potassium when H+ is high?
If H+ high, K+ not excreted.
What does the kidney exchange Na+ for?
Kidney can exchange Na+ ions for either H+ or K+ ions.
What happens to the heart when K+ is high?
High K+ impairs heart function.
How can pH be maintained at a constant value?
In order for pH to be maintained at a constant value:
INPUT of H+ = OUTPUT of H+
What is the major source for H+ and what is its formula?
Carbonic acid formation = major source of H+. Formula:
CO2 + H2O H2CO3 H+ + HCO3-
Carbonic anhydrase enzyme
What 2 things in the body that are involved in the regulation acid - base?
CAPILLARIES AND LUNGS
Meat proteins contain 2 inorganic acids name them both…
Meat proteins contain Sulphur and phosphorus to produce sulphuric and phosphoric acids.
These are strong acids and produce lots of H+ ions.
What food neutalises acids?
Fruit and vegs produces bases to neutalise acids.
What are 3 organic acids?
FATTY ACIDS
AMINO ACIDS
LACTIC ACID.
What are the 2 ingested acids?
CITRIC ACID
ACETIC ACID
What are the 3 things that regulate pH?
1) CHEMICAL BUFFER SYSTEMS:
2) THE RESPIRATORY SYSTEM
3) KIDNEYS
What are chemical buffer systems?
First line of defence
Mops up’ H+ ions
Mixture of substances that minimise pH changes
One substance gives free H+ as H+ falls
Another substance binds to free H+ as H+ increases
What is a Carbonic acid - bicarbonate buffer and what happens when there is a fall in H+ and an increase in H+?
Most important buffer for extracellular fluid in buffering changes other than generated by CO2
If H+ is added (fall in pH) they bind with carbonic acid (HCO3-) to give (bicarbonate) H2CO3
If H+ is removed (increase in pH) H2Co3 gives H+ + HCO3-.
Where is carbonic acid (HCO3-) and (bicarbonate) H2CO3 abundant?
H2CO3 and HCO3- are abundant in the extracellular fluid.
What organ regulates carbonic acid (HCO3-)?
Kidneys
What organ regulates (bicarbonate) H2CO3?
Lungs regulate H2CO3 (via CO2)
What is the Henderson-Hasselbalch equation?
pH = pKa + log10 ([A-]/[HA])
What is the function of a protein buffer system (5 things)?
1)Intercellular proteins and plasma proteins
2)Main intracellular mechanism
3) High protein concentration in intracellular fluid
4)Have acidic and basic groups
5)Groups give up or accept H+
What is the function of the haemoglobin buffer system (5 things)?
1) Buffers H+ from metabolically produced CO2
2) Oxyhaemoglobin gives O2 to tissues
3) Deoxygenated haemoglobin accepts H+
Hb + H+ = H-Hb
4) H+ released in lungs as haemoglobin picks up O2 as it has a lower affinity for H+.
5) H+ combines with bicarbonate in lungs to produce CO2 and H2O which is exhaled.
H+ + HCO3- = H2CO3 = CO2 + H2O
What is the function of a phosphate buffer system?
1) Main urinary buffer
2) Made up of:
- Acid phosphate NaH2PO4 to donate H-
- Basic phosphate Na2HPO4 to accept H+
Na2HPO4 + H+ NaH2PO4 + Na+
3)Low in extracellular fluid so not important
4)Used intracellularly and in urine
5)If high phosphate is consumed it is put in urine.
6)Used to remove H+ in kidney tubule to make excretion more efficient.
What is the function of the respiratory system (5 things)?
1) Second line of defence after buffers
2) Controls rate of CO2 removal
3) Regulates plasma PH
4) Moderate speed of effect - acts in minutes
5) Respiratory abnormalities reduce effects
What happens when there is increased arterial H+ ions and what does it result in?
Increased arterial H+ ions:
- Simulates peripheral chemoreceptors (carotid and aortic bodies) and central chemoreceptors in medulla (respiratory centre)
- Increases pulmonary ventilation via increased frequency of ventilation and tidal volume.
Results in:
- Removal of CO2
- Removal of H2CO3
- Removal of H+
What happens when there is a decrease in arterial H+ ions and what does it result in?
Decreased Arterial H+ ions:
- Results in reduced pulmonary ventilation via reduced frequency of ventilation and tidal volume via chemoreceptors
Results in:
- Increased CO2
- Increased H2CO3
- Increased H+
What is the function of the kidney system for acid - base regulation?
1) 3rd line of defence
2) Takes hrs to days to have effect
3) Most potent of all regulators
4) Can return pH totally to normal values (respiratory system can only rectify to 50- 70%)
What is the function of the kidneys in acid-base regulation?
- Remove H+ from blood
- Remove or conserve HCO3- in blood
How is H+ excreted in the kidneys (6 things)?
1) Removes H+ originating from sulphuric, phosphoric and lactic acids.
2) Small amount of H+ is filtered into kidney tubule
3) Majority of H+ is secreted into proximal, distal and collecting tubules.
4) Tubule cells automatically adjust secretion rate
5) Requires CO2 which limits the rate of process.
6) H+ can’t be reabsorbed.
How is bicarbonate excreted?
H+ in plasma is buffered by HCO3-
How can kidney influence pH?
- Variable reabsorption of HCO3-
- Variable addition of new HCO3- to plasma
How is bicarbonate (HCO3) reabsorbed (7 things)?
1) Process of H+ section adds HCO3- into plasma
2) HCO3- can’t diffuse through tubule cell lumen membrane from tubule fluid.
3) Filtered HCO3- combines with secreted H+ to give CO2 + H2O
4) CO2 diffuses in cell then produces H+ + HCO3-
5) HCO3- is reabsorbed into peritubular capillary
6) More H+ is secreted then HCO3- is filtered so all HCO3- is reabsorbed from filtrate.
7) New HCO3- is added to plasma from CO2 obtained from metabolism of tubule cell.
What is the kidneys response to acidosis (3 things)?
1) More H+ secreted by kidney tubule into tubule fluid - so urine contains more H+
2) Less HCO3- is filtered as it exists in blood plasma as H2CO3
3) More new HCO3- is put in plasma
What is the kidneys response to alkalosis (3 things) ?
1) More HCO3- is filtered into kidney tubule
2) Less H+ is secreted by kidney tubule
3) HCO3- can’t all be reabsorbed
4) More HCO3- is excreted in urine.
What happens during urine acidity?
Urine acidity:
1) H+ transporters can only secrete until tubule fluid is 800x more acidic (pH = 4.5 - 1%) than inside the tubule cell.
2) Urine must be buffered to remove free H+
Uses:
1) Phosphate buffer system:
Na2HPO4 + H+ = NaH2PO4 + Na+
2) Ammonia secretion
What happens during ammonia secretion (6 things)?
Ammonia secretion:
1) Tubule cells secrete ammonia into tubule fluid
2) Ammonia reacts with H+ in tubule fluid to reduce acidity
NH3 + H+ NH4+
3) Tubules cells are impermeable to NH4+ so it is excreted in urine
4) Glutamine is used to produce ammonia in tubule cells
5) Diffuses into tubule fluid
6) Production is stimulated by H+
What is hyperventilation?
- Lung disease
- Respiratory depression through drugs or disease
- Respiratory muscle weakness
- Breath hold
What is the function of compensation in the kidneys?
- Buffers mop up H+
- Kidneys conserve all filtered HCO3-
- Kidneys add HCO3- to plasma
- Kidneys secrete and excrete H+
What are the causes of hyperventilation?
- Fever
- Anxiety
- Aspirin poisoning
- High altitude
How is compensation used in terms of hyperventilation?
- Buffers liberate H+
- Low CO2/H+ inhibits ventilation
- Kidneys excrete HCO3-
- Kidneys conserve H+
How does metabolic acidosis come about?
- Loss of HCO3- in diarrhoea (HCO3- absorbed in gut)
- Diabetes produces keto acids which produces H+
- Strenuous exercises produces lactic acid
- Uremic acidosis in renal failure where H+ is not excreted and HCO3- is not reabsorbed
How does compensation occur for metabolic acidosis?
Compensation (except uremic acidosis):
- Buffers mop up H+
- Lungs remove more CO2
- Kidneys conserve filtered HCO3-
- Kidneys add HCOS- to plasma
- Kidneys secrete and excrete H-
How does metabolic alkalosis come about?
-Vomiting produces loss of H+ in gastric
Juice but HCO3- still absorbed into plasma
- Alkaline drugs e.g. NaHCO3
- Buffers liberate H+
- Ventilation is reduced to conserve CO2
- Kidneys excrete HCO3-
- Kidneys conserve H+
