Lecture 32

Question 1

What are the three places where water is reabsorbed in the nephron?

Answer 1

PCT, descending limb on nephron loop, collecting duct

Question 2

How much water is reabsorbed in the PCT?

Answer 2

67%

Question 3

How much water is reabsorbed in the descending limb of the nephron loop?

Answer 3

25%

Question 4

How much water is reabsorbed in the collecting duct?

Answer 4

2-8%

Question 5

What is reabsorption of water in the collecting duct determined by?

Answer 5

Hydration level

Question 6

How much water is excreted?

Answer 6

<1 - 6%

Question 7

What type of water reabsorption occurs in the PCT and the descending limb of the nephron loop?

Answer 7

Bulk reabsorption via leaky epithelia

Question 8

How much of the total water reabsorption occurs by bulk reabsorption?

Answer 8

92% (does not change)

Question 9

What type of water reabsorption occurs in the collecting duct?

Answer 9

Regulated reabsorption via tight epithelia

Question 10

How much of the total water reabsorption occurs in the collecting duct, what is this regulated by?

Answer 10

2-8% - regulated by antidiuretic hormone (ADH)

Question 11

What are the four places where sodium is reabsorbed in the nephron?

Answer 11

PCT, ascending limb on nephron loop, DCT and collecting duct

Question 12

How much sodium is reabsorbed in the PCT?

Answer 12

67%

Question 13

How much sodium is reabsorbed in the ascending limb of the nephron loop?

Answer 13

25%

Question 14

How much sodium is reabsorbed in the DCT?

Answer 14

5%

Question 15

How much sodium is reabsorbed in the collecting duct?

Answer 15

2-3%

Question 16

How much sodium is excreted?

Answer 16

<1%

Question 17

What type of sodium reabsorption occurs in the PCT and the ascending limb of the nephron loop?

Answer 17

Bulk reabsorption via leaky epithelia

Question 18

How much of the total sodium reabsorption occurs by bulk reabsorption?

Answer 18

92%

Question 19

What type of sodium reabsorption occurs in the DCT and the collecting duct?

Answer 19

Regulated reabsorption via tight epithelia

Question 20

How much of the total sodium reabsorption occurs by regulated reabsorption, and what is this regulated by?

Answer 20

7-8% - regulated by aldosterone

Question 21

What drives and regulates body water homeostasis?

Answer 21

Distribution of water, osmolarity of solutions, chances in osmolarity, reabsorption of water and sodium in nephron and effects of osmotic & volume changes on the kidney

Question 22

What is water reabsorption in the PCT driven by?

Answer 22

Na+ reabsorption

Question 23

What transporter transports sodium across the apical membrane?

Answer 23

Sodium-glucose cotransporter

Question 24

What is the driving force for the Sodium-glucose cotransporter?

Answer 24

Sodium gradient

Question 25

How is chloride attracted across the epithelial cell?

Answer 25

The positive charge on the sodium attracts the negative charge on the chloride, allowing it to go down its concentration gradient via the paracellular pathway

Question 26

How does Na+ facilitate water reabsorption?

Answer 26

Na+ and Cl- in the peritubular fluid increases the osmolarity, attracting water through aquaporins

Question 27

What do juxtamedullary nephrons cause in the nephron loop?

Answer 27

A hyper-osmotic medullary gradient

Question 28

What are changes in ECF osmolarity detected by?

Answer 28

Osmoreceptors in the hypothalamus

Question 29

What do the osmoreceptors stilulate?

Answer 29

The posterior pituitary gland to secrete more/less ADH

Question 30

What does ADH do?

Answer 30

Alters water permeability of the collecting duct cells by delivering/removing aquaporins in the apical membrane of CD cells

Question 31

Explain what happens to water during dehydration

Answer 31

Increased osmolarity in ECF, stimulates more ADH secretion for kidneys to increase water reabsorption and increase ECF volume

Question 32

Explain what happens to water during hyper-hydration

Answer 32

Decreased osmolarity in ECF, stimulates less ADH secretion for kidneys to decrease water reabsorption and decrease ECF volume

Question 33

What is an increase in ECF volume detected by

Answer 33

Cardiac muscle cells (because e.g. increased volume (plasma) means more blood is being pumped into your heart per beat, therefore stretch receptors are stimulated)

Question 34

What do the cardiac muscle cells stimulate?

Answer 34

The release of ANP

Question 35

What does ANP do?

Answer 35

Acts on kidneys to increase Na+ and water loss in urine to decrease ECF volume

Question 36

What is a decrease in ECF volume detected by?

Answer 36

Kidneys

Question 37

What do the kidneys stimulate?

Answer 37

Activation of RAAS and an increased release of ADH

Question 38

What does RAAS do?

Answer 38

Increases the release of aldosterone from the adrenal gland and therefore the delivery of more sodium channels to the apical membrane

Question 39

What does the increased release of ADH and aldosterone cause?

Answer 39

Decreased Na+ and water loss in urine

Question 40

What is found in normal urine?

Answer 40

Water, creatinin, urea, uric acid, H+, Na+, medications and toxins

Question 41

What is found in pathological (abnormal) urine?

Answer 41

Glucose, protein, blood, haemoglobin, white blood cells and bacteria

Question 42

What does normal urine look like?

Answer 42

Clear to light or dark amber (yellow) colours

Question 43

What does pathological (abnormal) urine look like?

Answer 43

Orange, red, brown, blue/green colours

Question 44

What could abnormal urine taste like?

Answer 44

Sweet from the presence of glucose

Question 45

What would be the cause of 'fruity' smelling urine?

Answer 45

Ketones from fasting, diabetes, or chronic alcohol abuse

Question 46

What could be the cause of 'rotten' smelling urine?

Answer 46

Bacterial infection of tumour