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Flashcards in Acid base physiology Deck (83)
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1

Hydrogen ion

Single free proton released from a hydrogen atom
- H+ exists in solution bound to water (H2O)

2

Acid

Molecule that releases hydrogen ions in solution
- HCl

3

Base

Molecule that can accept H ions in solution
- calcium carbonate

4

Hydrogen ions are very _____

Reactive!!
- alter structure and function of virtually every protein and enzyme in the body

5

Homeostasis requires control of _____

H+

6

Metabolic acidosis causes

- decreased myocardial contractility
- vasodilation
- reduced responsiveness to catecholamines
- impaired coagulation
- decreased cell function

7

Respiratory acidosis causes

Cerebral edema via vasodilation

8

H+ concentration is kept ____ relative to other ions

Very low
- 0.00004 mEq/L (pH 7.4)

9

pH formula

log (1/[H+]) = -log[H+]
- high [H+] = low pH
- low [H+] = high pH

10

Normal blood pH is ____

7.4 (7.35=7.45)
- arterial blood is 7.4
- venous blood is 7.35 (contains more CO2, which acts as an acid)

11

Physiologic limits of blood pH

6.8-8.0

12

Intracellular fluid pH is ____ than blood

Lower (6.0-7.4
- cellular metabolism produces H+

13

Urine pH

4.5-8.5

14

What are the 3 primary systems that regulate changes in [H+]?

- buffers: seconds (weakest)
- lungs (ventilation): minutes (stronger)
- kidneys: hours to days (strongest)

15

Is the body more efficient at dealing with acids or bases?

Acids

16

Buffer

Substance that can reversibly bind with H+
- accept or donate H+ to minimize changes in [H+] until balance can be restored

buffer + H+ Hbuffer

17

What are the 4 main buffers in the body?

- bicarb (extracellular)
- proteins (intracellular)
- phosphate (intracellular and renal tubules)
- ammonia (renal tubules) *most important in removing bicarb*

18

Bicarb buffer system

Consists of carbonic acid (H2CO3) and bicarb salt (NaHCO3)
- carbonic acid weakly dissociates
- bicarb salt almost completely dissociates
- carbonic anhydrase is abundant in lungs and kidney

19

Bicarb buffer system formula

CO2 + H2O H2CO3 H+ -HCO3

20

What happens if an acid is added to the bicarb buffer system?

Consumed by bicarbonate, driving the equation left
- carbon dioxide is produced (and exhaled)

21

What happens if a base is added to the system?

Consumed by carbonic acid, driving the equation to the right
- carbon dioxide is consume (and ventilation decreases)

22

The bicarb system is connected to the _____

Lungs
- both are dependent on each other
- ventilation (CO2) is required to keep the bicarb system working at max efficiency

23

Abnormalities in ventilation affect the _____

pH
- hypoventilation --> increased CO2 --> increased carbonic acid

24

The lungs thru ventilation, control extracellular [H+] and provides a second means to respond to changes in ____

[H+]

25

Minute ventilation

Tidal volume x respiratory rate

26

Ventilation has 2 main stimuli

- changes in blood carbon dioxide
- changes in blood oxygen

27

The body favors ___ control over ___

CO2; O2 control

28

The lungs are very effective at compensating for ____

Acidemia
- ventilation can be easily increased
- overall buffering capacity is 1-2x that of all other chemical buffers combined

29

The lungs are less effective at compensating for _____

Alkalemia
- if ventilation decreases too much, hypoxemia occurs
- the body won't starve itself of oxygen

30

Why are diseases that suppress ventilation life threatening?

The body has limited ways to immediately respond to the acid base effects of hypercapnea