Physiology 4 (easy)

Question 1

How much urea is reabsorbed?

Answer 1

50%

Question 2

How much amino acid reabsorbed?

Answer 2

100%

Question 3

How much creatine reabsorbed?

Answer 3

0%

Question 4

Roughly how many mls filtered fluid is reabsorbed in the proximal tubule?

Answer 4

80ml/min

Question 5

What is reabsorbed in the PT?

Answer 5

Sugars
Amino acids
Phosphate
Sulphate
Lactate

Question 6

What is secreted in the PT?

Answer 6

H+
Hippurates
Neurotransmitters
Bile pigments
Uric acid
Drugs
Toxins

Question 7

What is primary active transport?

Answer 7

Energy is directly required to operate the carrier and move the substrate against its concentration gradient

Question 8

What is secondary active transport?

Answer 8

The carrier molecule is transported coupled to the concentration gradient of an ion (usually Na+)

Question 9

What is facilitated diffusion?

Answer 9

Passive carrier-mediated transport of a substance down its concentration gradient

Question 10

Which transporter at basolateral membrane essential for Na+ reabsorption?

Answer 10

Na+/K+ ATPase

Question 11

How is glucose reabsorbed?

Answer 11

Luminal: co-transport
Basoalteral: facilitated diffusion, and also in exchange for K+ (might be primary active transport)

Question 12

Renal threshold for glucose reabsorption

i.e. Tm (transport maximum)

Answer 12

10-12 mmol/l

clearane of reabsorbed substance is not constant once Tm reached

Question 13

Percentage of all salt and water reabsorbed in the proximal tubule

Answer 13

67%

Question 14

Na+ reabsorption also drves reabsorption of what through the paracellular pathway?

Answer 14

Cl- !!!

Question 15

Is the tubular fluid iso-osmotic when it leaves the proximal tubule?

Answer 15

Yes (i.e. 300mosmol/l)

Question 16

Which part of the nephron is responsible for creating a cortico-medullary solute concentration gradient?

Answer 16

Loop of Henle

Question 17

Is urine hypotonic or hypertonic?

Answer 17

Hypotonic

Question 18

Which part of the loop of henle reabsorbs Na+ and Cl-?

Answer 18

Ascending limb

(thick - active transport
thin - passive)

Question 19

This part of loop of henle does not reabsorb NaCl and is highly permeable to water

Answer 19

Descending limb

Question 20

Is fluid entering the distal tubule iso-osmotic or hypo-osmotic?

Answer 20

Hypo-osmotic

Question 21

Where is urea absorbed etc?

Answer 21

50% of urea diffuses passively into the loop of Henle

• distal tubule not permeable to urea
• Collecting ducts absorbs 50% urea

Question 22

Effect of ADH on urea absorption?

Answer 22

ADH promotes urea absorption

Question 23

What is the purpose of the countercurrent multiplier?

Answer 23

-Concentrates the medullary interstitial fluid and enable the kidney to produce urine of different volume and concentration according to the amounts of circulating antidiuretic hormone (ADH = vasopressin)

Question 24

Vasa recta and the loop of henle

Answer 24

Blood osmolality rises as it dips down into the medulla (i.e. water loss, solute gained)

Blood osmolality falls as it rises back up into the cortex (i.e. water gained, solute lost)

Question 25

Purpose of the vasa recta

Answer 25

Passive exchange across the endothelium preserves medullary gradient - blood equilibrates at each layer.
Ensures that the solute is not washed away

Question 26

The high medullary osmolarity allows the production of hypertonic urine in the presence of

Answer 26

ADH

Question 27

What creates the medullary osmotic gradient?

Answer 27

The countercurrent multiplier and the urea cycle

the countercurrent exchanger (vasa recta) preserves that gradient