L45. Water Balance and Electrolyte

Question 1

How is water gained and produced?

Answer 1

Gained through diet

Produced through metabolism

Question 2

How is water lost?

Answer 2

Via sweat, urine and faeces

Question 3

Do the gains of water outweigh the losses?

Answer 3

Gains = losses

Question 4

Name one of the only factors under homeostatic control.

Answer 4

Urine excretion

Question 5

Name the 5 components of the kidney.

Answer 5

Glomerulus
Proximal convoluted tubule
Loop of henle
Distal convoluted tubule
Collecting duct

Question 6

Give another name for ADH

Answer 6

vasopressin

Question 7

What does the glomerulus do?

Answer 7

Filters plasma

Question 8

What does GFR stand for and what is the value per minute?

Answer 8

Glomerular filtration rate

120ml/minute

Question 9

Give the net filtration pressure in the glomerulus.

Answer 9

10-15mmHg

Question 10

What happens in the proximal convoluted tubule?

Answer 10

60-70% of glomerular filtrate is reabsorbed. It secretes H+ for acid/base balance

Question 11

What happens in the loop of henle?

Answer 11

Ascending limb’s active transport pumps determine urine concentration
Henle loop length determines urine concentration

Question 12

What is the role of the distal convoluted tubule?

Answer 12

Resorption of water, Na+, Cl-

Its activity is controlled by hormones, eg aldosterone

Question 13

What happens in the collecting ducts?

Answer 13

Water resorption by ADH

Question 14

Where is ADH produced, released and what does it control?

Answer 14

Produced in hypothalamus
Released from posterior pituitary
Controls water

Question 15

Which 2 regions does ADH act on in the kidneys?

Answer 15

Distal convoluted tubules

Collecting ducts

Question 16

What can increase ADH secretion?

Answer 16

Decreased ECF volume

Question 17

What are electrolytes? Give examples.

Answer 17

Ions present in ICF and ECF, eg Na+, K+ etc

Question 18

What does the renin-angiotensin-aldosterone system promote, and where?

Answer 18

Reabsorption of Na+ and H2O in the distal convoluted tubule.

Question 19

Which hormone has the opposite effect to aldosterone meaning it increases Na+ and H2O secretion?

Answer 19

ANH

Question 20

Describe an incidence of ADH hyposecretion.

Answer 20

Diabetes insipidus - lots of dilute urine

Question 21

Describe an incidence of ADH hypersecretion.

Answer 21

Water retention

Question 22

Why are potassium salts used in some toothpastes?

Answer 22

They desensitise sensitive dentine

Question 23

Describe the thinking behind K+ ions in toothpaste.

Answer 23

Ions diffuse along tubules, depolarise nerves and inactivate channels. This prolongs the refractory period (membrane potential does not return to resting potential). Not a long-term solution as the K+ cannot build up.