Acid Base Balance

Plasma has a similar composition to interstitial fluid/Intracellular fluid?

Plasma is in continuous contact with interstitial fluid, therefore similar make up

Salt

An ionic compound consisting of a cation other than hydrogen and an anion other than a hydroxide ion

pH formula for weak acids

A- is a base
HA is an acid
Ka is the acid dissociation constant

Does a strong acid have a high/low Ka and a high/low pKa

Strong acid: High Ka, Low pKa

Does a weak acid have a high/low Ka and a high/low pKa

Weak acid: Low Ka, High pKa

What does each buffer system buffer? Primary role?
(i) H2CO3:HCO3- buffer system
(ii) Protein buffer system
(iii) Haemoglobin buffer system
(iv) Phosphate buffer system

(i) ECF buffer
(ii) ICF (&ECF) buffer
(iii) Carbonic acid buffer
(iv) Urinary (&ICF) buffer

What are the 1st and 2nd lines of defence against a pH shift?

1st line: Chemical buffer system
- bicarbonate
- phosphate
- protein
2nd line: Physiological buffer system
- respiratory (CO2 excretion)
- renal (H+) excretion

Where & how do protein buffers (incl haemoglobin) work?

They work in the blood and the ICF
To buffer bases carboxyl groups on proteins give up H+
To buffer acids amino groups on proteins accept H+
Work almost immediately

How do respiratory buffer mechanisms work?

Body pH can be adjusted by changing rate and depth of breathing.
Exhalation works on volatile acids only.
Increased respiratory rate increases pH
(Takes several minutes to hours)

How do the kidneys buffer pH

Most effective pH regulator but takes hours to days
Excretes large amounts of acids & bases
Conserves & produces bicarbonate ions
If kidneys fail, pH balance fails

What pH levels = acidosis & alkalosis?

pH< 7.35 acidosis
pH > 7.45 alkalosis

When are respiratory/metabolic compensation used

If underlying problem is metabolic, hyperventilation or hypoventilation can help : respiratory compensation.
If problem is respiratory, renal mechanisms can bring about metabolic compensation.