Acid Base Regulation Flashcards
pH is a measure of ____ and is a function of ____
- acidity
- [H+]
pH range of ECF in body is…
6.8 - 7.8
Plasma pH is usually around…
7.35 - 7.45
Definition of acid:
substance that donates H+
Acidosis occurs when blood pH is…
< 7.35
Definition of base:
substance that removes H+ from body fluids
Alkalosis occurs when blood pH is…
> 7.45
Which factors produce changes in ECF pH?
- metabolic factors
- respiratory factors (CO2)
- changes in kidney excretion of bicarb and H+
How does metabolism of fats and carbs affect pH?
- large amount of CO2 is created
- volatile acid creates H+
- eliminated by lungs
How does metabolism of amino acids affect pH?
- creates sulfuric acid and HCl
- has nonvolatile acid (offset by production of HCO3-)
A meat containing diet will have a net acid production that is greater/less than HCO3-
greater than
Abnormal insulin levels leads to the production of…
ketoacids
How does CO2 have an effect on pH?
- inversely related to pH
- hypoxia -> increased acids
How does changes in kidney excretion affect pH?
- acid addition > excretion = acidosis
- acid removal > excretion = alkalosis
pH is regulated by…
- buffers
- respiratory rate and depth
- kidney excretion of H+ and bicarb ions
What is the first line of defense for changes in pH?
buffers: minimize change in pH when acids are added
- neutralizes acid or base but doesn’t eliminate it from body
T/F: ECF buffering occurs slowly
F, it’s instantaneous
Steps of bicarb buffering system:
- CO2 produced and reacts with ECF water to make carbonic acid
- carbonic acid dissociates into H+ and bicarb
- increasing ECF bicarb pushes reaction to the left to prevent H+ release
What is the rate limiting reaction in the steps of the bicarb buffering system?
hydration of CO2
- gets sped up by carbonic anhydrase
What is the principal ECF buffer?
bicarb
Normal bicarb concentration range:
23-25 mEq/L
Bicarb is regulated by both the…
lungs and kidneys
What does buffering processes create and remove?
- creates Na+ salts
- removes bicarb
How do the kidneys help with buffering?
- excretes acid salts
- returns bicarb to blood
How does the respiratory system help with buffering?
clears CO2 via respiration
- mostly intracellularly
Aside from bicarb, what are some other ECF buffers?
- phosphate
- plasma proteins
What is the second line of defense against changes in pH?
respiratory regulation of pH
- occurs because of changes to pCO2
What determines the pCO2 in the body?
ventilation rate
- increased = decreased pCO2
What are important regulators during respiratory regulation?
- blood pCO2
- pH
Blood pCO2 and pH are monitored by…
- central chemoreceptors (medulla for CSF)
- peripheral chemoreceptors (aortic and carotid bodies for plasma)
Effect of metabolic acidosis on ventilation rate?
- increased to clear CO2
- occurs after several minutes
Effect of metabolic alkalosis on ventilation rate?
decreased
What is the third line of defense against changes in pH?
renal regulation
- takes a few days to return to normal
Bicarb is _____ if body is basic, and ______ if body is acidic
- excreted
- reabsorbed
What is the primary urinary buffer?
phosphate
Phosphate is under regulatory control of…
- thyroid calcitonin (TCT)
- parathyroid hormone (PTH)
How does bicarb get formed?
- CO2 diffuses from plasma into PCT
2. carbonic anhydrase creates H+ and bicarb
How does glutamine produce new bicarb?
- systemic acidosis stimulates glutamine metabolism in PCT after bicarb loss
- 2 NH4+ created
- gets secreted and bicarb gets returned to circulation
How many bicarbs are created from metabolism of one glutamine?
2
Signs of metabolic acidosis:
- decreased [bicarb]
- decreased blood pH
- increased [anion]
Compensatory mechanisms for metabolic acidosis:
- buffers
- increase respiration rate
- kidney reabsorbs more bicarb
- increase urine [NH4+], which makes more bicarb
Signs of metabolic alkalosis:
- increased [bicarb]
- increased blood pH
How does metabolic alkalosis occur?
- vomiting
- ingestion of alkali
- hemorrhage
Compensatory mechanisms for metabolic alkalosis:
- buffers
- decrease in respiration
- increase excretion of bicarb by decreasing reabsorption
Signs of respiratory acidosis:
- increased pCO2
- decreased blood pH
How does respiratory acidosis occur?
- poor gas exchange across alveoli
- impaired gas diffusion
Compensatory mechanisms for respiratory acidosis:
- ICF buffering
- increased bicarb reabsorption
- increased NH4+ excretion
Signs of respiratory alkalosis:
- decreased pCO2
- increased blood pH
How does respiratory alkalosis occur?
increased gas exchange
Compensatory mechanisms for respiratory alkalosis:
- ICF buffering
- decreased excretion of bicarb
- decreased NH4+ excretion
