Acid-Base and Electrolyte Balance

Question 1

What are electrolytes?

Answer 1

Minerals present in blood and other body fluids

They play a vital role in the functioning of the human body

Question 2

2 ways water is regulated by the body

Answer 2

1. Thirst center

2. ADH/Vasopressin

Question 3

Thirst center

Answer 3

In the hypothalamus

Senses an increase in osmolarity –> increases thirst and water intake –> restore osmolarity back to normal

Question 4

Antidiuretic Hormone

Answer 4

Released from the posterior pituitary gland in response to an increase in osmolarity or decrease in BP
Increases the number of aquaporins in the kidneys (increases water retention to restore balance)

Question 5

Most Na is reabsorbed in which 2 places?

Answer 5

Proximal convoluted tubule

Thick ascending limb

Question 6

Aldosterone

Answer 6

Released from the adrenal gland
Stimulates Na reabsorption in the distal convoluted tubule/collecting duct in exchange for K
Water follows Na

Question 7

Natriuretic peptides

Answer 7

Atrial and brain natriuretic peptides
Release from the heart
Activated by myocardial stretch
Decrease Na reabsorption in the DCT/collecting duct
Decrease renin (and hence aldosterone)
Net effect is a decrease in plasma Na and volume

Question 8

Na concentration

1. Extracellular
2. Intracellular

Answer 8

1. 135-145 mM

2. 4-10 mM

Question 9

Hyponatremia

Answer 9

When plasma [ ] is less than 135 mM

Can be from Na depletion, water excess, or Na and water retention (but more water than Na is retained)

Question 10

K concentrations

1. Extracellular
2. Intracellular

Answer 10

1. 3.5-5.0 mM

2. 150 mM

Question 11

3 things that can cause significant K shift

Answer 11

Acid base balance
Insulin
Beta-adrenergic agonists

Question 12

Normal H+ concentration in arterial blood

Answer 12

35-45 nmol/L

Arterial pH is slightly alkaline

Question 13

2 reasons for tight regulation of pH

Answer 13

Proper enzyme structure and function

H+ gradient between inner and outer mitochondrial membrane drives ox phos

Question 14

5 main acids produces by the body

Answer 14

Carbonic acid
Sulphuric acid
Phosphoric acid
Ketoacids
Lactic acid

Question 15

4 buffers in the body and which ones are the main intra or extra cellular ones

Answer 15

Bicarbonate (major extracellular buffer)
Phosphate
Protein
Hemoglobin (major intracellular buffer)

Question 16

For an arterial sample

1. Normal pH
2. Normal pCO2
3. Normal HCO3-

Answer 16

1. 7.35-7.45
2. 35-45 mmHg
3. 21-28 mmol/L

Question 17

Metabolic disorders are compensated by…

How fast?

Answer 17

Compensated by the lungs (change in ventilation rate)

Take effect within seconds to minutes of pH change

Question 18

Respiratory disorders are compensated by…

How fast?

Answer 18

Compensation by the kidneys (change excretion/reabsorption of H+/bicarb)
Requires hours to days to take effect