Phys 3

Question 1

Reabsorption in PCT

Answer 1

• location of most active reabsorption
• all glucose and aa
• 60-80% of Na+
• 75-85% of water
• K+
• Urea

Question 2

PCT

• overall change to filtrate
• secretion

Answer 2

• filtrate volume reduced by 80%

- secretion of nitrogenous wastes

Question 3

Descending loop of Henle

• permeability
• filtrate changes

Answer 3

• freely permeable to water
• not permeable to NaCl
• filtrate is concentrated by water resorption

Question 4

why does water exit descending loop of Henle?

Answer 4

exits based on osmotic gradient of cortical and medullary interstitial fluid

Question 5

Ascending loop of Henle

• permeability
• filtrate changes

Answer 5

• freely permeable to NaCl
• not permeable to water
• dilute filtrate formed

Question 6

Why does Na+ leave the Ascending loop of Henle, what does it contribute to

Answer 6

actively transported out

- contributes to high osmolarity of the medullary ECF

Question 7

DCT

• absorption
• secretion

Answer 7

selective absorption and secretion
Absorption
- HCO3-
- Na+ (under Aldosterone control)
- Water (ADH control)

secretion:
- NH4 and H+

Question 8

What happens to filtrate as it moves through DCT

Answer 8

becomes more concentrated as water is absorbed

Question 9

CD reabsorption & secretion

Answer 9

• urine is concentrated along medulla
• reabsorption/secretion to maintain blood pH (K+, H+, HCO3-, Cl-)
• urea diffuses via transporters to medulla, helps contribute to high osmolarity

Question 10

Tubular secretion

- functions

Answer 10

• dispose of unwanted substances not in filtrate such as drugs
• eliminate unwanted substances that have been reabsorbed by passive processes
• K+ elimination (via aldosterone)
• Control of blood pH

Question 11

How does tubular secretion change as blood becomes acidic

Answer 11

• actively secrete H+ into filtrate (acidify urine)

- reabsorb HCO3- and K+

Question 12

How does tubular secretion change as blood becomes alkaline

Answer 12

• HCO3- is secreted

Question 13

How is the flow of blood related to the flow through the nephron?

Answer 13

countercurrent

• creates opportunities for osmotic movement with help from highly osmotic gradient of medullary interstitium
• as blood flows past ascending limb absorbs ions, becomes hypertonic
• then when passes descending limb water easily moves into blood dt osmotic pressure of ions

Question 14

Vasa recta

- function

Answer 14

• maintain osmotic gradient
• deliver nutrient supply
• sluggish blood flow
• freely permeable to water and salt (vs. loop of Henle which is differentially permeable)

Question 15

Volume of water in

• the body
• ICF
• ECF

Answer 15

Total: 40 L
ICF: 25 L
ECF: 15 L (interstitial fluid and plasma)

Question 16

Composition of body fluids

• what maintains
• ICF ion
• ECF ion

Answer 16

• Na/K pump
• ICF: K+
• ECF: Na+

*bc osmolality is equal between ECF and ICF, the NET change between the two is zero even though lots of ion, etc. flow between

Question 17

Tonicity

definition

Answer 17

ability of a solution to change the tone of cells

Question 18

Isotonic

- example

Answer 18

Physiological saline soln (PSS)

- 0.9% sodium w/v, 308 mOsmol

Question 19

what happens to cells in solutions that are:
Hypotonic
Hypertonic

Answer 19

hypo: swell, lysis
hyper: shrivel, crenation

Question 20

What happens when there is a mismatch in osmolality of body fluids between electrolyte intake and loss

Answer 20

change in osmolality of body fluids - physiologic issues that must be fixed

Question 21

What two things happen when there is an increase osmolality of ECF?

Answer 21

• thirst: drink more water, dilute ECF

- ADH secretion: water retention, dilute ECF

Question 22

Thirst drive for water balance

- two stimuli

Answer 22

• decreased volume of ECF

- increased osmolality of ECF

Question 23

What happens when increased osmolality of ECF occurs?

Answer 23

• decreased saliva secretion
• dry mouth
• drink
• increased water = decreased osmolality

Question 24

what happens when decreased volume of ECF occurs

Answer 24

• stim osmorelceptors in hypothalamic thirst center
• sensation of thirst,
• drink
• increased water = increased volume

Question 25

ADH - released from what - why released?

Answer 25

- released from posterior pituitary | - in response to hypothalamic stimulus

Question 26

ADH | - 2 receptor types

Answer 26

Osmoreceptors - in hypothalamus - depolarize when >285 mOsm/kg Baroreceptors - great veins, L/R atria, PV - respond to low volume

Question 27

ADH | - what other stimuli cause release

Answer 27

- pain - nausea - surgical stress - Ang II in response to hypovolemia

Question 28

ADH | - principle effect

Answer 28

- water retention by kidney | - causes filtrate to become concentrated

Question 29

ADH | - receptor

Answer 29

- V2 receptor - on CD cells - stimulates insertion of aquaporin 2 into the apical membranes

Question 30

where are aquaporins stored

Answer 30

endosomes | - ADH causes rapid translocation to cell membrane

Question 31

ADH | - effects

Answer 31

- water enters hypertonic interstitum of renal pyramids, is reabsorbed - osmotic pressure of body fluids decreases - urine concentrates, volume decreases

Question 32

In conditions of good hydration and no ADH describe the - urine - water loss/gain

Answer 32

- urine is hypotonic to plasma - urine volume is increased - net water loss

Question 33

what is the most important determinant of ECF volume

Answer 33

Na+

Question 34

Sodium - regulation linked to what - regulated by what 3

Answer 34

- regulation linked to blood pressure and blood volume | - regulated by aldosterone, renin, natriuretic peptides (ANP, BNP)

Question 35

what regulatory molecule has the most influence over sodium in the ECF?

Answer 35

Aldosterone

Question 36

Aldosterone

Answer 36

- steroid hormone | - produced and released by adrenal cortex

Question 37

Aldosterone is released in response to (2)

Answer 37

1. renin from kidney (via angiotensin II) | 2. High serum K+

Question 38

Function of aldosterone

Answer 38

1. increase renal Na+ reabsorption and K+ secretion (water follows Na+) 2. receptors on DCT and CT

Question 39

Renin - released from what - in response to what

Answer 39

``` - released from juxtaglomerular cells in response to: 1. decreased stretch due to low volume/bp 2. decreased filtrate osmolarity 3. direct SNS stimulation ```

Question 40

What is the function of Renin/angiotensin system

Answer 40

- cleave angiotensinogen to release angiotensin I | - ACE action produces angiotensin II

Question 41

Functions (3) of Angiotensin II

Answer 41

1. vasoconstriction - increases peripheral vascular resistance (after load) - increases bp 2. aldosterone secretion from renal cortex - reabsorb Na+, increase blood volume and bp - secretion of K+ 3. feedback inhibition of renin

Question 42

Natriuretic peptides | - two types

Answer 42

1. ANP: atrial natriuretic peptide (atrial myocytes) | 2. BNP: B-type natriuretic peptide (ventricle)

Question 43

Natriuretic peptides | - released in response to what

Answer 43

stretch - increased blood volume/bp

Question 44

Natriuretic peptides | - action

Answer 44

- decrease blood volume/bp - kidney: * increase GFR dt vasodilation * inhibit Na+ reabsorption by tubules * decrease renin - inhibit aldosterone - vascular smooth muscle relaxation (vasodilation)

Question 45

Potassium - essential for what - other very important function

Answer 45

- essential for membrane potential, esp in heart | - important in pH buffering systems (H+ movement is balanced by K+ countermovement)

Question 46

What controls K+ balance

Answer 46

renal mechanisms under influence of aldosterone (directly sensitive to increased K+)

Question 47

How does body remove excess K+?

Answer 47

Aldosterone causes increased Na+ reabsorption by tubules | - concomitant secretion of K+ due to Na/K pump