Renal Control of Acid-Base Balance Flashcards

Question

**H2CO3 has a pKa at 6.1.** What does this mean?

Answer 1

* It is the pKa where the buffer is 1/2 saturated. * Meaning that 1/2 of the buffer exists as [**H2CO3**] and 1/2 is [**dissociated HCO3- and H+**].

Answer 2

CA is unstable and spontaneously depolarizes in either direction. CO2+ H2O ⇔ H2CO3 ⇔ H+ + HCO3- CO2 is made by aerobic metabolism and can be blown out by the lungs. HCO3 is made by anaerobic metabolism and ingested acids. It is slowly made and regulated by the kidneys . Normally, we have 600,000/free H+.

Answer 3

Increase CO2= increase H2CO3= Increase H+ and HCO3 (but a v small amount)= decrease pH

Answer 4

Decrease CO2= decrease H2CO3= decrease H+ and HCO3 (but a v small amount)= **increase pH**

Answer 5

The pKa is the pH at which the buffer, acting as a sponge, has sopped up half of the H+ it can hold. You will see small changes in pH in the buffer zone.

Answer 6

1. 70% is transported as bicarb 2. 23% is transported with Hb (HbCO2) 3. 7% is dissolved

Answer 7

The pH of the ECF is buffered because the ICF takes in H+ and exchanges it for a K+ (which has higher concentration inside of the cell).

Answer 8

The ECF is buffered because the ICF donates a H+ and takes in a K+ from the ECF.

Answer 9

allows us to **predict the pH** of a buffered solution, given its pK, the concentration of conjugate base, and the concentration of conjugate acid. pH =6.1 + log[HCO₃-]/[H₂CO₃] pH= 6.1 + log[HCO₃]/0.03 \* P_CO2 **_{Usually Pco2=40; [HCO3-]= 24}**

Answer 10

**20:1** ## Footnote Therefore, through our kidney and lungs, our body will try to keep the 20:1 ratio.

Answer 11

**acidosis** ## Footnote **(deficiency in HCO3-; excess of H+/CO2)**

Answer 12

**Alkalosis** ## Footnote **(Excess HCO3-, deficiency of H+/CO2)**

Answer 13

**Bicarb** is controlled by the kidneys, slow with large capacity. **CO2** is controlled by the lungs, fast with limited capacity.

Answer 14

**99%** of filtered bicarb is reabsorbed in the nephron. **85%** is reabsorbed in the PT, with a small amount being absorbed in the thick ascending lumb and a small "fine tuning" occuring in the DT and collecting duct.

Answer 15

* 85% of Bicarb is reabsorbed in the PT via **Na/H+ ATPase** * HCO3 in the lumen binds with H+ --\> carbonic acid * Carbonic anhydrase allows it to dissociate--\>CO2 and H20. * CO2 and H20 is uptaken passively into the cells of the proximal tubule where carbonic anhydrase reforms it into H+ and HCO3-. * The HCO3- is shuttled out of the cell through either a **Na/3HCO3- symporter,** or a **HCO3-/Cl- chloride antiporter**. * The H+ ion is shuttled back into the intratubular fluid via a Na/ H+ antiporter. The bicarbonate sodium symporter is an example of how the concentration gradient being created of bicarbonate within the cell carries the sodium against its concentration gradient (into the ECF) without having to use the Na/K ATPase.

Answer 16

1. Decrease in plasma HCO3- concentration --\> decrease in pH --\> increase H+ secretion 2. Increase in P_CO2 --\> decrease in pH –\> increase H+ secretion.

Answer 17

1. Increase in filtered load of bicarb will secrete more H+ so that we can reabsorb the HCO3-. 2. Decrease in ECF volume 3. Increase in angiotensin II--\> stimulates Na+/H+ exchange in the proximal tubule 4. Increase in aldosterone--\> stimulates H+ ATPase in the intercalated cells of the collecting duct 5. Hypokalemia

Answer 18

In intercalated A cells (active in acidic conditions), we want to remove H+ and reabsorb bicarb. 1. CO2 from the blood --\> intercalated A cells. 2. CO2+ H20--[CA]--\> H2CO3--\> H+ and HCO3-. 3. **H+ ATPase on the apical membrane** pushes H+ ions out of the cells. 4. In order to keep excreted H+ ions, we need to buffer it in the urine. Thus, NaHPO4 will bind a H--\> NaH2PO4--\> secrete it in the urine. 5. The NEW bicarb in the cells moves from the cell--\> blood via **HCO3-/Cl- exchanger.** ----Aldosterone will promote the reabsorption of HCO3- by increasing the activity of the H+ ATPase, which is located on the apical membrane and moves the H+ out----

Answer 19

**Reclaim HCO3-**

Answer 20

Glutamine has 2 ammonias. The kidney has a infinite amount of glutamine and can make as much as it needs to act as a buffer. 1. Cells in the proximal tubule rely on glutamine for energy, producing ammonia as a byproduct 2. NH3 and H+ from the Na+/H+ antiporter enters the lumen and combine, to create ammonium (NH4+) 3. At the thick ascending LoH, NH4+ is transported by Na, K and 2Cl in place of K--\> interstitium 4. In the interstium, it enters an equillbrium between ammonium (NH4+) and ammonia (NH3) 5. NH3 diffuses through cell of collecting duct and enters the lumen 6. In the tubular fluid, NH3 buffers H+--\> NH4+ 7. H+ is removed from the bicarb reabsorption loop and drags it into the urine. For every H+ removed, one HCO3- is freed **Thus, ammonia is used to reclaim bicarb.**

Answer 21

**Alpha intercalated cells--\>** _secrete H+_ and _reabsorbs HCO3-_ **Beta intercalated cells--\>** _reabsorb H+_ and _secrete HCO3-_

Answer 22

* H+ is secreted into the tubular fluid and combines with HCO3- to form CO2 and H20, which is then reabsorbed in the cell. * H+ can also be buffered by NH3--\> NH4+ and excreted, creating new bicarb, while bicarb is absorbed.

Answer 23

NAE = (U_NH4+ ✕ V) + (U_TA ✕ V) - (U_HCO3-✕ V) * *Net acid excretion* *is equal to the urinary concentration of ammonia times urine flow rate, plus the urinary concentration of titratable acids (primarily phosphate) times urinary flow rate, minus urinary concentration of bicarbonate times urinary flow rate.* * It must be equal to production of non-volatile sources of H+ ions (anaerobic breakdown of glucose, oxidation of cystein and oxidation of phosphoproteins)

Answer 24

TA- Salts that are mainly phosphate, but can be other constituents of urine, such as creatine. They make up ~1/3 of NAE

Answer 25

* No. It has a high pK, meaning that no H+ can be removed when titrating to a pH of 7.4. * It is responsible for about 2/3 of net acid excretion

Answer 26

**little**

Answer 27

**Causes of acidosis:** * Decrease in (HCO3-) * Increase in acid (H+) **---pH decreases--** Two things will happen: 1. **Respiratory compensation (lungs)** 1. Hyperventilation--\> decrease P_CO2--\> decrease CO2 and H20--\> Decrease in H2CO3--\> decrease in H+--\> increase pH 2. **Renal correction (kidneys)**- will do what they can to make more bicarb and secrete more H+ 1. Increased acid titration--\> 1. Increased buffering of H: [NH3+ H+--\> NH4+] and [HPO4 + H+ ---\> H2PO4] 2. Increases bicarb regeneration and increases acid excretion **---increase pH---**

Answer 28

**Anion gap= Na+ - (Cl- + HCO3-)** ## Footnote Anion gap is the value of unmeasured anions in the plasma. It is normally 8-16 mEq/L.

Answer 29

**MUDPILERS** ## Footnote 1. **Methanol** 2. **Uremia** 3. **DKA/alcoholic KA** 4. **Paraldehyde** 5. **Isoniazid** 6. **Lactic acidosis** 7. **EtOH/Ethylene Glycol** 8. **Rhabdo/renal failure** 9. **Salicylates**

Answer 30

**HARDUPS** ## Footnote **1. Hyperalimentation** **2. Acetazolamide** **3. Renal tubular acidosis** **4. Diarrhea** **5. Utero-pelvic shunt** **6. Post-hypocapnia** **7. Spironolactone**

Answer 31

* In type I renal tubular acidosis, the alpha intercalated cant secrete hydrogen. * --\> decreases the ability of NH3 and HPO to buffer that hydrogen creating "new" bicarbonate. * **Plasma K is usually low.**

Answer 32

* Impaired HCO3 reabsorption in the **proximal tubule.** * K is usually low.

Answer 33

* Mild acidosis is asymptomatic. However, when pH is \<7.10 (or higher if it developed rapidly), it can cause **nausea, vomiting and malaise.** * Respiratory compensation: large, deep breaths without dyspnea

Answer 34

**Causes of metabolic alkalosis** 1. Increase in HCO3- 2. Decrease in H+ **---Increase in pH---** **Respiratory compensation** * Hypoventilation--\> increase in P_CO2--\> Increase in CO2 +H20--\> increase in H2CO3--\> increase in H+--\> decrease pH **Renal Correction** * Decrease reabsorption of HCO3- --\> increases excretion of HCO3- --\> decreases pH * Decrease acid titration--\> decreases acid loss by down-regulating the binding of H+ to NH3 and HPO4- * (-) in binding of H+ to NH3--\> decreases acid excretion--\> decreases pH * (-) bind binding of H+ to HPO4- --\> decreases in bicarb regeneration--\> decreases pH **---decrease pH---**

Answer 35

**CLEVER PD** ## Footnote 1. **Contraction** 2. **Licorice** 3. **Endo: (Conn, Cushing, [Bartter])** 4. **Vomiting** (loss of H+, HCO3- remains in the blood, maintained by volume contraction, hypokalemia) 5. **Excess alkali** 6. **Refeeding alkalosis** 7. **Post-hypercapnia** 8. **Diuretics** (volume contraction increases HCO3- reabsorption d/t increase angiotensin II and aldosterone)

Answer 36

**Mild**: signs and symptoms of underlying disorder **More severe**: increase HCO3- in the blood--\> HCO3- can begin to bind calcium --\> hypocalcemia. * Hypocalcemia will cause neuromuscular excitability, delirium, tetany, and seizures. * Hypocalcemia can also cause arrhythmias, much the same as hypokalemia.

Answer 37

**Cause: decreased ventilation** * Increased P_CO2 * Increased H2CO3 * Increased H+ **---Decreases pH---** **Renal compensation** (increases production of NH3 and HPO4- to make more bicarb) * Increased acid titration * [NH3- + H+--\> NH4]--\> increased acid excretion * [HPO4- +H+ --\> HPO4-]--\> increased bicarb regeneration **---Increase pH---**

Answer 38

**Acute: _CANS_** 1. CNS depression 2. Airway obstruction 3. Neuromuscular disorders 4. Severe pneumonia, embolism, edema **Chronic** 1. COPD 2. Anything chronic that leads to impaired ventilation **---they're selling acidic air in CANS---**

Answer 39

Acute (neurological issues) * HA, confusion, anxiety, drowsiness, stupor, tremors, convulsions, coma If slowly developing, stable * may be well tolerated

Answer 40

**Cause: increased ventilation** * Decrease P_CO2 * Decrease H2CO3 * Decrease H+ **---Increase pH---** **Renal Compensation** * Decreased acid titration * Decrease buffering of H+ by NH3- --\> decreased acid excretion * Decreased buffering of H+ by HPO4- --\> decreased bicarb regneration **---decrease pH---**

Answer 41

**CHAMPS** ## Footnote 1. **CNS disease** 2. **Hypoxia\* (high altitude)** 3. **Anxiety** 4. **Mechanical ventilators** 5. **Progesterone** 6. **Salicyclates and sepsis**

Answer 42

1. Acute respiratory alkalosis--\> light headed, confusion, crapms and syncome due to change in cerebral blood flow and pH 1. Tachypnea or hypernea is often the only sign 2. Severe- carpopedal aspasm due to decreases levels of hypocalcemia 2. Chronic--\> usually asymptomatic; no signs

Renal Control of Acid-Base Balance Flashcards

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