Alterations in Acid/Base Balance

Question 1

What pH is Acid-base balance achieved?

Answer 1

pH - 7.37 to 7.43

Question 2

Define body fluids

Answer 2

formded as end products of cellular metabolism of carbohydrates, proteinsm fats as well as loss of base in stools

Question 3

Why is maintaining pH important?

Answer 3

Slight deviations from the normal range can result in pronounced, systemic and potentially fatal changes in metabolic activity

For example, Na/K pump works 50% less effectively when pH falls by 1 pH

Question 4

Define buffers

Answer 4

compounds that bind H ions when [H+] rises and releases them when the [H+] falls

• absorbs extra H+ and OH- significantly without changing pH

Two types of buffers
- proteins in the body and the bicarbonate buffer system

Question 5

Renal Buffering System

Answer 5

Distal tubule of the kidney

• secretion of H+ into urine
• reabsorption of bicarbonate (HCO3-)

Cellular ion exchange system

• reabsorption of K+ instead of H+ during states of acidosis
• reabsorption of H+ instead of K during states of alkalosis

Question 6

Electrolyte Homeostasis

Answer 6

Clinically measures plasma levels

• Plasma levels are the net result of:
• intake
• absorption
• distribution
• excretion

Question 7

Potassium Regulation

Answer 7

K+ balance is controlled in collecting ducts by changing the amount of potassium secreted into filtrate

• excessive K+ is excreted by collecting ducts
• when K + levels are low, amount of secretion + excretion is kept to a minimum
• K+ plasma levels determine secretion
• Aldosterone stimulates K+ secretion
• Collecting ducts: Na+ reabsorbed = K+ secreted

Increased ECF K+ around adrenal cortex causes:

• release of aldosterone
• K+ secretion
• K+ controls own ECF concentration via feedbkac regulation of aldosterone release

Question 8

Causes of Hypokalaemia

Answer 8

• Diarrhoea
• Diuresis
• Excessive aldosterone
• Dietary intake
• Treatment of diabetic ketoacidosis with insulin

Question 9

Effects of Hypokalaemia

Answer 9

• Interferes with neuromuscular function
• Parethasias “pins and needles”
• lower GI tract motility - loss of appetite
• severe K+ deficiencies - weak respiratory muscles
• cardiac dysrythmias - prolonged repolarisation
• renal failure - polyuria

Question 10

Causes of Hyperkalaemia

Answer 10

• Excessive oral intake
• renal failure
• deficit of aldosterone
• crush injuries or burns
• prolonged or severe acidosis

Question 11

Effects of Hyperkalaemia

Answer 11

• Muscle weakness
• paralysis
• impairment of neuromuscular activity
• Fatigue, nausea, paresthaesias
• ECG show cardiac dysrhythmias - cardiac arrest