Renal Mechanism of Acid Base Balance Flashcards
Acid-Base Balance
- Acid-base balance is one of the most important of the body’s _______ mechanisms
- Acid-base balance refers to regulation of __________ ion concentration in body fluids
- Precise regulation of ___ at the cellular level is necessary for survival
- Slight pH changes have dramatic effects on cellular metabolism
homeostatic
hydrogen
pH
Acid-Base Balance
• Achieved by:
– Utilization of chemical buffers in ECF & ICF
– Respiratory mechanisms that excrete ____
– Renal mechanisms that reabsorb ___________ and secrete hydrogen ions
• Normal range of arterial pH is____-_______
CO2
bicarbonate
7.37 – 7.42
Acid Production in the Body
- CO2 - end-product of aerobic metabolism; ___________ acid
- Fixed Acid – non-volatile
volatile
Buffer Mechanism
- Buffers – are substances that prevent marked change in pH of solution when an acid or base is added to it; consist of weak acid (or its acid salt) and basic salt of that acid
- Buffer pairs present in body fluids – mainly _________ ______, proteins, hemoglobin, acid phosphate, and sodium and potassium salts of these weak acids
carbonic acid
Buffer Mechanism-1
Action of buffers to prevent marked changes in pH
Nonvolatile acids, such as hydrochloric acid, lactic acid, and ketone bodies, buffered mainly by _______ __________
sodium bicarbonate
Buffer Mechanism-2
Action of buffers to prevent marked changes in pH
Volatile acids, chiefly carbonic acid, buffered mainly by _______ salts of hemoglobin and oxyhemoglobin
potassium
Buffer Mechanism-3
Action of buffers to prevent marked changes in pH
The _____ shift makes it possible for carbonic acid to be buffered in the red blood cell and then carried as bicarbonate in the plasma
chloride
Buffer Mechanism-4
Action of buffers to prevent marked changes in pH
Bases are buffered mainly by ______ ________(when homeostasis at pH 7.4 exists)
carbonic acid
Buffer Mechanism-5
Action of buffers to prevent marked changes in pH
The Henderson-Hasselbalch equation is a mathematical formula that explains the relationship between __________ ion concentration of body fluids and the ratio of base bicarbonate to ______ ______
hydrogen
carbonic acid
Mechanisms of Hydrogen Ion Regulation
A. [H+] is precisely regulated at (pH range 7.2 - 7.4)
1. Body fluid chemical buffers (rapid but \_\_\_\_\_\_\_\_\_\_) 1- bicarbonate 2- ammonia 3- proteins 4 - phosphate
B. Lungs (____, eliminates CO2)
C. Kidneys (_______, powerful); eliminates non-volatile acids
- secretes H+
- reabsorbs HCO3-
- generates new HCO3-
temporary
rapid
slow
Buffer Systems in the Body x 4
___________ : most important ECF buffer
____________ : important renal tubular buffer
_________ : important renal tubular buffer #2
___________ : important intracellular buffers
Bicarbonate
Phosphate
Ammonia
Proteins
(____-______% of buffering is in the cells)
60-70
Importance of Buffer Systems
Normal H+ concentration = 0.00004 mmol/L
Amount of non-volatile acid produced ~ 60-80 mmol/day 80 mmol/42 L = 1.9 mmol/L
= 47,500 times > normal H+ concentration
Know
Bicarbonate Buffer System
Effectiveness of buffer system depends on:
- concentration of ___________
- pK of system and pH of body fluids
reactants
Respiratory Regulation of Acid-Base Balance
Feedback Gain = 1.0 to 3.0 (corrects 50 to ___%)
75
Bicarbonate Buffer System
Is the most important buffer in ________
fluid even though the concentration of the components are low and pK of the system is 6.1, which is not very close to normal extracellular fluid pH (7.4).
Reason: the components of the system (CO2 and HCO3-) are closely regulated by the _____ and the _________
extracellular
lungs
kidneys
Urinary Mechanism
- Reabsorption of HCO3-
- Excretion of fixed H+ produced from ________ and phospholipid catabolism
protein
Bicarbonate Reabsorption-1
Effect of filtered load of HCO3-
– ________ HCO3- exceeds the reabsorptive capacity
Excess
Bicarbonate Reabsorption-2
Effect of ECF volume
– ECF volume expansion ________ HCO3- reabsorption
– ECF volume contraction _________ HCO3- reabsorption
– Angiotensin II mechanism
inhibits
stimulates
Bicarbonate Reabsorption-3
Effect of CO2
– Increase in pCO2 = _________ in HCO3- reabsorption
– Decrease in pCO2 = _________ in HCO3- reabsorption
increase
decrease
Excretion of H+ as NH4+–1
Effect of acidosis on NH3 synthesis
– Acidosis increases _________ metabolism
glutamine
Excretion of H+ as NH4+—2
Effect of plasma K+ concentration on NH3
synthesis
– Hyperkalemia _______ NH3 synthesis, causing type 4 renal tubular acidosis
– Hypokalemia _________ NH3 synthesis
inhibits
stimulates
Acid-Base DISORDERS
- _________ acid-base disorders – primary disorders involving HCO3-
- _______ acid-base disorders – primary disorders involving CO2
- Therefore, there are four simple acid-base disorders.
- There can also be mixed acid-base disorders.
Metabolic
Respiratory
Plasma Anion Gap-1
- A measurement useful in diagnosis of acid- base disorders
- Based on principle of ________________
- Unmeasured anions = gap
- Normal range: 8-16 mEq/L
electroneutrality
Plasma Anion Gap-2
- Useful primarily in the differential diagnosis of ___________ diagnosis
- If HCO3- is replaced by unmeasured anions, the calculated anion gap is __________
- If HCO3- is replaced by Cl-, the calculated anion gap is normal
metabolic
increased
Anion Gap as a Diagnostic Tool
In body fluids: total ________ = total anions
Anion Gap – is defined as the difference between unmeasured anions and unmeasured cations
Normal anion gap = 8 - 16 mEq / L
Cations
Plasma Anion Gap-3
• Metabolic acidosis with ______ anion gap
– Diabetic ketoacidosis – Lactic acidosis – Salicylate poisoning – Methanol poisoning – Ethylene glycol poisoning – Chronic renal failure
increased
Plasma Anion Gap-4
• Metabolic acidosis with _______ anion gap
• No organic anion is accumulated
– Diarrhea
– Renal tubular acidosis
normal
Renal Compensation for Acidosis
Increased addition of HCO3- to body by kidneys (increased H+ loss by ________)
This can increase to as high as 500 mmol/day
kidneys
Renal Compensation for Alkalosis
HCO3- excretion can ______ markedly in alkalosis
increase
Renal Compensations for Acid-Base Disorders
- Acidosis:
- _________ H+ excretion
- increased HCO3- reabsorption - production of new HCO3- - Alkalosis:
- ___________ H+ excretion
- decreased HCO3- reabsorption - loss of HCO3- in urine
increased
decreased
Acid-Base Disturbances
Respiratory ________ :
- brain damage
- pneumonia
- emphysema
- other lung disorders
Acidosis
Acid-Base Disturbances
Respiratory __________:
- high altitude
- psychic (fear, pain, etc)
Alkalosis
Acid-Base Disturbances
Metabolic __________:
- increased base intake (e.g. NaHCO3) - vomiting gastric acid
- mineralocorticoid excess
- overuse of diuretics (except carbonic anhydrase inhibitors)
Alkalosis
