Integrative Physiology III Regulation of Acid Base Balance Flashcards by Olivia Bellantoni

what is the pH of arterial blood, venous blood and interstitial fluid

-arterial: 7.4
- venous: 7.35
- interstitial: 7.35

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why is pH in venous blood and intersitital fluid lower

higher concentration of carbon dioxide due to carbonic anhydrase reaction so more H+

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what is the normal ECF [H+]

0.00004 mEq/L

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what are the sources for hydrogen ion gain

generation of H+ from CO2
production of nonvolatile acids from the metabolism of proteins and other organic molecules
gain of H+ due to loss of HCO3- in diarrhea or other nongastric GI fluids
gain of H+ due to loss of HCO3- in the urine

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what are the sources of H+ loss

-utilization of H+ in the metabolism of various organic anions
- loss of H+ in vomit
- loss of H+ in urine
- hyperventilation

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how much do fixed acids add to acid production a day

80 mEq/day

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what are sources of fixed acid/non volatile production

-protein catabolism: sulfuric acid and HCL
- phospholipid catabolism: phosphoric acid
-exercsie, hypoxia: lactic acid
- post absorptive state, DM: acetoacetic acid and beta hydroxy butyric acids
- nucleoprotein metabolism: uric acid

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how are fixed acids filtered

all excreted by the kidneys

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what are the three primary systems that regulate the [H+] in body fluids

-chemical
-respiratory
- kidneys

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describe how chemically [H+] is regulated

-acid base buffer systems
-instantaneous
-does not add or remove H+ but keeps it tied up until balance can be re established

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what are the buffers of ECF and which is more powerful

-bicarbonate buffer system- more powerful
- phosphate buffer system

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what are CO2 and HCO3- regulated by

respiratory and renal systems

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what is the phosphate buffer system

H2PO4- -> H+ + HPO4(2-)

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what is the phosphate buffer system important for

buffering renal tubular fluids and ICF

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where does 60-70% of total chemical buffering occur

inside the cells

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how can H+ enter cells

-CO2
- produced: lactic, acetoacetic, beta hydroxyl butyric acid
- H+/K+ exchange

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what are the intracellular buffers

-proteins (Hb and deoxyHb)
- organic phosphates such as ATP, ADP, AMP, glucose-1-PO4, and 2,3 BPG

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how does the respiratory system regulate [H+]

-regulates removal of CO2
-changes alveolar ventilation
- occurs fast: seconds to minutes

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resting normal human produces _____ of CO2 per minute

200mL

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what 3 processes facilitate CO2 transport

-10% dissolved in plasma
- 25% binds to amino groups in Hb
- 65% carbonic acid in RBCs

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what does alveolar exchange do

removes CO2

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what do disorders of the respiratory system lead to

respiratory alkalosis or acidosis

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what can changes in alveolar ventilation function to restroe

pH following acid base disturbances

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how do the kidneys function to regulate [H+]

-excrete an acidic or alkaline urine
- slow: hours to days
-most powerful of the acid/base regulatory systems

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how do kidneys regulate pH

by altering plasma [HCO3-] -secrete H+ -reabsorb, produce, or excrete HCO3-

where does most HCO3- absorption and H+ secretion occur

proximal tubule

for each HCO3- reabsorbed _____ must be secreted

a H+

how is H+ secreted

by secondary active transport

where does secondary active secretion of H+ occur

PT, TAL, and early distal tubule

_____ of filtered HCO3- reabsorbed and requires _____ of H+ to be secreted

95%; 4000 mEg

where is HCO3- titrated with H+

in tubule lumen

what is the rate of tubule H+ secretion

4400 mEq/day

what is the renal load of HCO3- per day

4320 mEq/day

in alkalosis what is the relationship with HCO3- load and H+ secretion

HCO3- load > H+ secretion and excess HCO3- will be excreted

in acidosis what is the relationship between H+ secretion and HCO3- load

H+ secretion > HCO3- load and excess H+ is secreted

what is excess H+ excretion a function of

late DT and CD

what percentage of H+ secretion is late DT and CD responsible for

only 5% but its enough to create maximally acidified urine

what systems are used for excess H+ excretion

Phosphate and glutamine/NH4+

what does abnormal H+ production induce

renal compensation

where does primary active secretion of H+ occur

in the alpha intercalated cells of late distal and collecting tubules

where does the phosphate buffer system act in the nephron

PT, TAL, and early distal tubule

when does the phosphate buffer system come into play

when secreted H+ exceeds filtered load of HCO3-, H+ can bind to phosphate buffer system

what is the result of H+ combining with a buffer other than HCO3-

new HCO3- is added to the ECF

what happens to most filtered phosphate

it gets reabsorbed so theres only a small amount available to interact with H+ in filtrate

what is the maximum amount of excess H+ that can be buffered and excreted

500 mEq/day

describe the ammonia buffer system

-NH3 produced from protein metabolism in liver, converted into urea and glutamine -in PT,TAL, and DT, NH4+ is added to filtrate following glutamine metabolism and represents acid secretion - in CD, NH3 is secreted into lumen where it combines with H+ to form NH4+ -results in new HCO3- added to ECF

what percent of acid excreted and new HCO3- added to ECF does the ammonia buffer system account for

50% of each

H+ secretion by tubular epithelium is necessary for:

-HCO3- reabsorption -addition of new HCO3- to ECF - acid excretion -rate of secretion must be carefully controlled to maintain acid-base homeostasis

under normal conditions: acid secretion needs to be enough to:

- reabsorb almost all filtered HCO3- - rid the body of non-volatile acids produced during metabolism

why is acid secretion decreased during alkalosis

-not all filtered HCO3- is reabsorbed - HCO3- is excreted -No NH4+ or H2PO4-, no non-volatile acid excreted, no new HCO3- added

why is acid secretion increased during acidosis

- almost all filtered HCO3- is reabsorbed - NH4+ and H2PO4- generated, acid excreted, new HCO3- added

what are the two most important stimuli that increase H+ secretion by tubules

-increase in Pco2 of ECF - increase [H+]ECF

what factors increase H+ secretion and HCO3- reabsorption

-increase in Pco2 - increase H+ and decrease HCO3- - increase ANG II - increase aldosterone - hypokalemia - alkalosis

what factors decrease H+ secretion and HCO3- reabosrption

-decreased Pco2 - decreased H+ and increased HCO3- - decreased ANG II - decreased aldosterone - hyperkalemia - acidosis

what are the types of acid-base disturbances

- respiratory acidosis - metabolic acidosis - respiratory alkalosis - metabolic alkalosis

what happens in respiratory acidosis

- problems with ventilation or gas exchange: hypoventilation, PE, COPD -increased PCO2

what is the compensation for respiratory acidosis

- buffer of body -renal compensation -reabsorb all filtered HCO3- -secrete excess H+ and add new HCO3- to ECF ( increased glutamine metabolism and NH4+ excretion)

what is metabolic acidosis

- a decrease in pH not associated with an increase in CO2 levels

what happens in metabolic acidosis

- failure of kidney to excrete metabolic wastes (renal failure or addisons) - formation of excess amounts of metabolic acid (ketoacidosis) - increased input of metabolic acids - loss of base from body

what is the compensation for metabolic acidosis

-buffer of body -renal compensation: reabsorb all filtered HCO3-, secrete excess H+ and add new HCO3- to ECF -respiratory compensation: compensatory increase in alveolar ventilation in response to metabolic acid

what happens in respiratory alkalosis

- excessive ventilation leading to decreased PCO2 -rare

what is the compensation for respiratory alkalosis

-buffer of body -renal compensation: increased HCO3- excretion, decreased H+ excretion

what is metabolic alkalosis

-an increase in pH not associated with a decrease in CO2 levels

what causes metabolic alkalosis

- diuretics -excess aldosterone -excessive vomiting - ingestion of alkaline drugs

what is the compensation for metabolic alkalosis

- buffer of body -renal compensation: increased HCO3- excretion, decreased H+ excretion - respiratory compensation: compensatory decrease in alveolar ventilation in response to metabolic alkalosis

what is the primary abnormality in respiratory alkalosis and acidosis

CO2 change

what is the primary abnormality in metabolic acidosis and alkalosis

HCO3- change

what are the levels of H+, HCO3-, and CO2 in respiratory acidosis

-H+: high - HCO3-: high - CO2: high

what are the levels of H+, HCO3-, and CO2 in respiratory alkalosis

- H+: low - HCO3-: low -CO2: low

what are the levels of H+, HCO3-, and CO2 in metabolic acidosis

-H+: high - HCO3-: low - CO2: low

what are the levels of H+, HCO3-, and CO2 in metabolic alkalosis

-H+: low - HCO3-: high - CO2: high

what is the normal concentration of HCO3-

24 mEq/L

what is the normal concentration of PCO2

40 mmHg

Integrative Physiology III Regulation of Acid Base Balance Flashcards

(73 cards)