Urinary System 3

Question 1

Osmotic Pressure

Answer 1

Solutes/Solution

Question 2

What is reabsorbed in the Descending Loop of Henle?

Answer 2

Water - 15%

Question 3

What is Obligatory water reabsorption?
How much is absorbed in the Proximal Tubule and DL of Henle?

Answer 3

Obligatory water reabsorption – water that moves following solutes
* 65% in proximal tubule.
* 15% in the descending loop of Henle.
* Total: ~80%

Question 4

What is reabsorbed in the Ascending Loop of Henle?

Answer 4

Ascending loop of Henle:
Reabsorption
* Sodium – 25%.
* Chloride – 35%.
* Potassium – 25%.
* Water – no movement
(Need all 3 elements for reabsorption to take place)
(Potassium is active - low to high)
See Diagram

Question 5

What is reabsorbed and discreted in the Distal tubule and collecting duct?

Answer 5

Distal tubule and collecting duct:
Reabsorption
* Sodium – 6-9%.
Secretion
* Potassium – variable amount; adjusted for dietary intake, aldosterone hormonal levels
* no Potassium channel on the basolateral membrane, only on apical
* Sodium - facilitate diffusion

Question 6

What is the RAA System?

Answer 6

Renin – angiotensin – aldosterone

Question 7

What Occurs in Part 1 of the RAA System?
(4)

Answer 7

Part 1 – formation of angiotensin II in blood:
* Several pathways to juxtaglomerular (JG) cells secretion/release of renin

• Liver releases Angiotensinogen (inactive) into blood continually.
• Converted to active angiotensin I under the influence of renin.
• Angiotensin I to II by angiotensin converting enzyme (ACE)*

Question 8

dehydration(9)

Answer 8

Part 1 of RAA

Question 9

What does renin do?

Answer 9

converts inactive angiotensinogen to angiotensin I

Question 10

What converts angiotensin I to angiotensin II?

Answer 10

angiotensin-converting enzyme (ACE)

mainly from lung/kidney endothelial cells

Question 11

What Occurs in Part 2 of the RAA System?

Answer 11

Part 2 – secretion/release of aldosterone into blood:
* Increase of Angiotensin II and K+ in blood stimulates adrenal gland (adrenal cortex outer layer)

Secretion/release of aldosterone.
* Binds collecting duct cells.
* Increases apical membrane channels and
basolateral primary pumps.
* More ion movement and more water following sodium

Question 12

part 2 of RAA map

Answer 12

Question 13

What is Facultative Water absorption?

Answer 13

Facultative water reabsorption – adapting to need
* Variable amount (range from 0 – 19.8%); hormone-regulated.
* Under normal hydration conditions:
* 19 % reabsorption
* 1 % urinary excretion (1 – 2 L/day)

Question 13

What is Antidiuretic hormone?
(aka vasopressin)

Answer 13

Antidiuretic hormone (ADH) is a hormone that regulates the body’s water balance by increasing the reabsorption of water in the kidneys, leading to the concentration of urine and a decrease in urine volume.

• Number of aquaporins in distal tubule and collecting duct variable; virtually absent in this part of renal tubule unless ADH present.
• ADH causes the insertion of aquaporins on the apical membrane of the distal tubule and collecting duct

Question 13

How much Water is reabsorbed/Urinary Secretion when we are Overhydrated/Dehydrated?

Answer 13

Dehydration – 19.8% water reabsorbed
(0.2% urinary excretion);
largely due to ADH presence increasing the number of aquaporins.

Overhydration – as low as 0% water reabsorbed
(20% urinary excretion);
largely due to ADH absence decreasing number aquaporins

(never 0% urinary secretion)

Question 14

what would happen in an individual with no or minimal ADH?

Answer 14

not enough water movement due to a lack of pathways

Question 15

How are Water Reabsorption and Excretion affected by ADH during Dehydration and Sweat Loss?

Answer 15

Question 16

How are Water Reabsorption and Excretion affected by ADH during Overhydration?

Answer 16

slide 9

Question 17

What can inhibit the secretion of ADH?

Answer 17

Caffeine, alcohol: inhibit secretion of ADH. (more piss)

Diabetes insipidus: failure to secrete, release, respond to ADH (urine output up to 25L/day)

Question 18

What is Diabetes insipidus?

Answer 18

Diabetes insipidus: failure to secrete, release, respond to ADH (urine output up to 25L/day)

Question 19

Atrial Natriuretic Peptide (ANP) effect on Sodium

Answer 19

• Altered plasma volume will alter the distention (stretch) of atria.
• Distension controls ANP secretion and release.
• Decrease sodium reabsorption mainly in kidney proximal tubules and collecting ducts.
• Will increase urinary water excretion as water follows sodium.
• Can also inhibit the release of aldosterone and ADH

Question 20

How does increase in activity affect sodium regulation?

Answer 20