Acid and base physiology

Question 1

What is alkalemia vs acidemia?

Answer 1

1. arterial pH >7.45
   
   2. arterial pH <7.35

Question 2

What is Resp acid

Answer 2

CO2

Controlled by VA

Excreted by the lungs

Question 2

Metabolic fixed acids

Answer 2

All acids other then H2CO3

Excreted from kidneys

Question 3

Defences to imbalance

Answer 3

Chemical buffering

Respiratory control (arterial CO2)

Renal mechanism (H+ and HCO3)

Question 4

Wen do buffers bind vs release H+

Answer 4

1. bind when pH decreases
   
   2. release when pH increase

Question 5

Describe the bicarbonate buffer

(what)
(formula)

Answer 5

Predominant ECF buffer

Forms weak acid (pH only slight increase)

HA + NAHCO3 –> HCO3 + salt

Question 6

Describe the phosphate buffer

(what)
(formula)

Answer 6

Important ICF buffer

Forms a weak acid

HCL + NaHPO4 –> NAH2PO4 + NaCl

Question 7

Describe the protein buffer

(what)

Answer 7

AAs w organic acid groups (COOH) dissociate to release H+

Exposed groups can also accept H+

Question 8

What is the isohydric principle?

Answer 8

Change in one buffer = change in all

Question 9

What is the most important ECF buffer system?

Answer 9

CO2 + H20 <–> J2Co3 <–> H+ + HCO3-

Uses CA to catalyse

Question 10

What is the value of PCO2 at normal pH?

Answer 10

40

Question 11

What is the ratio of HCO3: H+ at normal pH?

Answer 11

20:1

Question 12

What is the normal HCO3 at normal pH?

Answer 12

24

Question 13

How long does resp response take and how does this compare to other acid bases responses?

Answer 13

Minutes to hrs (slower than chemical)

Question 14

What is the resp response to acid base imbalance?

Answer 14

Alterations in ventilation –> alter PCO2

Question 15

What is the resp response to acidosis?

Answer 15

Increased RR due to hypercapnia (central CRs stimulated) and metabolically activated H+ (peripheral CR activated)

Question 16

What is the resp response to alkalosis?

Answer 16

Decreased RR and breathing due to hypocapnia (Central CRs stimulated) and metabolic decrease H+ (peripheral CRs stimulated)

Question 17

What are the steps of the renal response?

Answer 17

H+ secreted in exchange for Na

H+ combines with Bicarbonate

CO2 reabsorbed and bicarbonate reabsorbed in blood

Question 18

How is HCO3 generated from the excretion of buffered H+?

Answer 18

Active H+ secretion

H+ held in tubular fluid via phosphate buffers

Bicarbonate reabsorbed

Question 19

How is HCO3 generated from excretion of buffered NH4?

Answer 19

Excrete acid

Generate 2 new bicarbonates

Question 20

What may cause:

a) Resp disorder

b) metabolic disorder

Answer 20

a) Primary changes in PCO2 levels

b) Primary change in [HCO3]

Question 21

What may cause respiratory alkalosis?

Answer 21

Excess CO2 excretion and hyperventilation

P- pain

P- panic

P- pregnancy

P- asPrin

P- hyPoxia

Question 21

What may cause respiratory acidosis?

Answer 21

Co2 Accumulation and hypoventilation

N- Neuromuscular

A- Airway obstruction

I- raised ICP

L- Lung pathology (COPD, Pneuomonia)

E- Epilepsy

D- Drugs (sedatives, analgesics, paralytics

Question 22

What causes metabolic acidosis?

Answer 22

Excess alcohol

Diarrhoea

Intense exercise

Starvation/ diabetic crisis

Question 23

What causes metabolic alkalosis?

Answer 23

Vomiting Excess antacids Constipation

Question 24

What does a Low HCO3 and PCO2 indicate?

Answer 24

= metabolic Aci or Resp Alk

Question 25

What does a High HCO3 and PCO2 indicate?

Answer 25

= metabolic alk or Resp Aci

Question 26

What does HCO3 and PCO2 going in opposite directions indicate ?

Answer 26

= mixed