Kin 191: Urinary System (Physiology)

Front 1

Describe the 3 needs of nephron in order to perform its filtering mechanism.

Back 1

1. semipermeable / selective membrane

2. two flow systems

i. fluid/solute in/out system

ii. waste out system

3. pressure (fluid) and concentration (solute) gradient

Front 2

List the 8 homeostatic kidney functions

Back 2

1. regulation of blood ionic composition

2. regulation of blood pH

3. regulation of blood volume

4. regulation of blood pressure

5. regulation of blood glucose level

6. maintenance of blood osmotic level

7. production of hormones

8. excretion of metabolic waste/foreign substances

Front 3

List the 3 ions that is regulated in blood composition

Back 3

- Na+

- K+

- Cl-

Front 4

Describe "obligatory mechanism", provide an example that occurs in the urinary system

Back 4

- a process where a substance is obligated to follow another substance

- ie: H2O following Na+ ; other substances following H2O

Front 5

How do we regulate blood pH?

Back 5

- through elimination of H+ or take up of HCO3- when blood pH is too acidic

- through elimination of HCO3- or take up of H+ when blood pH is too basic

Front 6

What is the relationship of blood volume and blood pressure?

Back 6

- directly proportional – therefore when we want to alter BP, we can alter BV (and vice versa)

- BP inc when BV inc; BP dec when BV dec

Front 7

What happens to blood volume during dehydration?

Back 7

- low blood volume and low blood pressure

Front 8

What is diuresis? What does it mean when a substance is diuretic?

Back 8

- excretion of H2O in urine

- a substance that causes excretion of H2O

Front 9

What enzyme is involved in regulation of blood pressure?

Back 9

- renin

Front 10

Define osmolarity

Back 10

- the concentration of a solution expressed as the total # of solute particles per L of the solution

Front 11

How can osmolarity be altered?

Back 11

- changing the # of particles (particle is unspecified – does not matter what kind of particle is altered, osmolarity still changes)

- changing the volume

Front 12

How is ionic concentration and osmolarity different?

Back 12

- osmolarity can be altered with non-specified particles

- ionic concentration can be altered with the respective ion

- ie: only inc/dec Na+ can alter the ion concentration of Na+ in blood whereas adding any particle can alter osmolarity of fluid

Front 13

What hormone is produced by the kidney for its homeostatic function?

Back 13

- erythropoietin (EPO)

Front 14

Briefly describe EPO

Back 14

- erythropoietin is involved in blood doping to increase O2-carrying blood cells – beneficial in sports

Front 15

Describe blood glucose regulation

Back 15

- can be indirect or direct via substances like amino acid glutamine

- direct regulation: determines how much we of certain substances are retained or excreted

- indirect regulation: occurs through conversion of amino acids to glucose (ie: glutamine –> glucose)

Front 16

What is gluconeogenesis?

Back 16

- formation of glucose from substances other than monosaccharides or glycogen

Front 17

What happens when we retain too much glutamine?

Back 17

- since glutamine produces glucose, too much glucose production may result into diabetes

- diabetes is detected through urine test when glucose is present in urine

Front 18

Provide examples of drugs or toxins that are excreted by the kidney

Back 18

- penicillin

- morphine

- histamine

Front 19

Provide examples of metabolic wastes or foreign substances that are excreted by the kidney

Back 19

- Nitrogen molecules: ammonia, urea

- creatine

Front 20

Name the 3 types of organs that the kidney can function as

Back 20

Kidney can function as:

- excretory organ

- regulatory organ

- endocrine organ

Front 21

What are the functions of the kidney as an excretory organ? (2)

Back 21

- excretion of waste and toxins

- excretion of excess water

Front 22

What are the functions of the kidney as a regulatory organ? (5)

Back 22

- regulations of:

1. blood ion composition

2. blood pH

3. blood volume or pressure

4. blood osmolarity

5. blood glucose level

Front 23

What is the function of the kidney as an endocrine organ? (1)

Back 23

- production of erythropoietin (EPO)

Front 24

What is the excretion equation?

Back 24

glomerular filtration + secretion - reabsorption

Front 25

What are the 3 basic functions of the nephron to maintain homeostasis of blood volume and composition?

Back 25

1. glomerular filtration

2. tubular reabsorption

3. tubular secretion

Front 26

Describe the operation of the nephron in maintaining homeostasis of blood volume blood composition. (3)

- Include the products of the process, and what they contain.

Back 26

1. Filtration from blood plasma into nephron

2. Tubular reabsorption from fluid into blood

3. Tubular secretion from blood into fluid

- Products:

a. Urine = contains secreted substances

b. Blood = contains reabsorbed substances

Front 27

Define: glomerular filtrate

Back 27

- the fluid or solute that enters the capsular space

- usually in volume

Front 28

What are the 3 principles of filtration?

Back 28

1. to force fluids and solutes through a membrane through pressure

2. filtration is the same in glomerular capillaries and bodily capillaries

3. however, there is more volume in glomerular capillaries than bodily capillaries

Front 29

Define: filtration fraction

Back 29

- the fraction of plasma in afferent arterioles that becomes the filtrate

- usually in %

Front 30

What are the 3 features that enhances glomerulus filtering capacity?

Back 30

1. large filtration surface area

2. thin and porous filtration membrane that makes it leaky

3. high level of glomerular capillary blood pressure

Front 31

What are the 3 main pressures involved in glomerular filtration?

Back 31

1. GBHP: Glomerular Blood Hydrostatic Pressure

2. CHP: Capsular Hydrostatic Pressure

3. BCOP: Blood Colloid Osmotic Pressure

Front 32

Define: GBHP (Glomerular Blood Hydrostatic Pressure)

Back 32

- the BP in glomerular capillaries

Front 33

Define: CHP (Capsular Hydrostatic Pressure)

Back 33

- the hydrostatic pressure against the filtration membrane by fluid already in capsular space

Front 34

Define: BCOP (Blood Colloid Osmotic Pressure)

Back 34

- the pressure due to proteins present in blood plasma

Front 35

Which of the 3 main pressure promotes glomerular filtration?

Back 35

- GBHP

Front 36

Which of the 3 main pressure opposes glomerular filtration?

Back 36

- CHP

- BCOP

Front 37

What is the product of GBHP, CHP and BCOP?

Back 37

- NFP: Net Filtration Pressure

Front 38

Describe NFP (Net Filtration Pressure)

Back 38

- an additive pressure (products of GBHP, CHP, BCOP)

- directly proportional to GFR (high NFP = high GFR)

- positive NFP: promotes filtration – fluid is leaving glomerular capsule

- negative NFP: does not favour filtration

Front 39

In what unit are GBHP, CHP, BCOP and NFP measured?

Back 39

- mmHg

Front 40

Describe what occurs when GFR is too high (high GFR = high systemic blood pressure)

Back 40

- substances pass renal tubules too quickly an are not reabsorbed

- transport maximums are reached and therefore there is no time to reabsorb

Front 41

Describe what occurs when GFR is too low (low GFR = low systemic blood pressure)

Back 41

- nearly all substances reabsorbed and some waste products not adequately excreted

- not enough fluid available to eliminate metabolic waste

Front 42

Define: GFR

Back 42

- Glomerular filtrate rate is the amount of filtrate formed by both kidneys each minute

Front 43

What requires kidneys to maintain a relatively constant GFR?

Back 43

- Homeostasis

Front 44

How do we control GFR? Name the 3 types of GFR regulation processes.

Back 44

- by controlling blood flow going into glomerulus

1. Renal Autoregulation

2. Neural Regulation

3. Hormonal Regulation

Front 45

Describe Renal Autoregulation. What are the 2 parts of RA?

Back 45

- RA is an intrinsic renal mechanism to maintain GFR despite changes in systemic blood pressure.

- RA allows the kidneys to adjust its own resistance to blood flow.

- 2 parts:

1. Myogenic mechanism

2. Tubuloglomerular feedback

Front 46

True or False: GFR can change over a day

Back 46

- False. GFR constant over a fairly wide range so normal day-to-day activities do not result in much change to H2O and solute excretion

Front 47

Which renal regulation is slower, which one is faster? Why?

Back 47

- Fast: Myogenic mechanism – it only requires afferent arterioles to respond to changing systemic blood pressure

- Slow: Tubuloglomerular feedback – because it involves more processes like receptors, JGA and afferent arterioles

Front 48

Describe: myogenic mechanism

Back 48

- smooth muscle cells in afferent arterioles respond to changing systemic blood pressure (SBP)

- the lumen of arteriole is altered depending on whether SBP is inc or dec.

- this mechanism responds within seconds of blood pressure change

Front 49

What happens in myogenic mechanism when SBP is increasing?

Back 49

- a.a. is stretched = constricted

- therefore, blood flow is restricted into glomerulus

Front 50

What happens in myogenic mechanism when SBP is decreasing?

Back 50

- a.a. is relaxed = dilate

- therefore, blood flow is increased into glomerulus

Front 51

What is the ultimate result whether SBP is increasing or decreasing in myogenic mechanism?

Back 51

- both results in maintained normal GFR

Front 52

Describe Renal Autoregulation from stimulus (high GFR) to negative feedback.

Back 52

1. Stimulus: increasing GFR due to high systemic blood pressure

2. Macula densa cells of JGA acts as the receptors which detects inc. of GFR (inc. of Na+, Cl- and H2O)

3. JGA decreases secretion of NO

4. low NO (a vasodilator) causes afferent arterioles to constrict

5. constricted a.a. decreases blood flow through glomerulus and therefore dec. GFR

6. eventually GFR returns to norm

Front 53

How does secretion of NO, afferent arterioles and blood flow change in Renal Autoregulation when the stimulus is high GFR? low GFR?

Back 53

High GFR:

- decreased secretion of NO

- constricted afferent arterioles

- decreased blood flow

Low GFR

- increased secretion of NO

- dilated afferent arterioles

- increased blood flow

Front 54

What causes the vasoconstriction in Neural Regulation?

Back 54

- norepinephrine released by Autonomic NS fibres

Front 55

What stimulation is required in Neural Regulation?

Back 55

- strong stimulation that can overcome renal autoregulation through exercise or hemorrhage

Front 56

Describe Neural Regulation

Back 56

1. strong stimulation through exercise or hemorrhage

2. ANS fibres release norepinephrine causing vasoconstriction of a.a.

3. constricted a.a. reduce urine output

4. since less blood is involved due to constricted a.a, more blood is available for other organs (shunting)

Front 57

What division of ANS is involved in Neural Regulation?

Back 57

- sympathetic only

*note: Neural Regulation is a one way pathway – only activates sympathetic division and only constriction of a.a. occurs

Front 58

What hormones are included in Hormonal Regulation? (2)

What are the functions of these hormones?

Back 58

1. Angiotensin II (A. II): since it's a strong vasoconstrictor, it constricts afferents and efferents, diminishing GFR

2. Atrial Natriuretic Peptide (ANP): relaxation of cells causes increasing capillary SA and GFR in response to stretch of the cardiac atria (blood volume increase)

Front 59

What is the function of secretion?

Back 59

- helps to manage pH and rid the body of toxic and foreign substances

Front 60

What is the function of reabsorption?

Back 60

- returns most of the filtered H2O and many of the filtered solutes to the bloodstream

Front 61

What types of transport mechanisms are present in reabsorption and secretion? (3 passive, 2 active)

Describe each mechanism.

Back 61

Passive (w/o energy):

1. Diffusion: moves substances from high conc. to low conc.

2. Facilitated Diffusion: diffusion that requires a membrane potential for movement

3. Osmosis: the movement of H2O from high conc. to low conc.

Active (w/ energy):

1. Primary Active Transport: the energy derived from ATP is used to "pump" a substance across a membrane

2. Secondary Active Transport: the energy stored in an ion's electrochemical gradient drives another substance across the membrane

Front 62

Define: Transport Maximum (Tm)

Back 62

- each type of transport has an upper limit on how fast it can work

Front 63

What are the two types of reabsorption routes?

Describe each route.

Back 63

1. Paracellular Reabsorption: passive diffusion; between adjacent tubule cells

- Pathway: tubule lumen –>interstitial fluid –> peritubular cap.

2. Transcellular Reabsorption: passive and active processes; through and individual tubule cell

- Pathway: tubule lumen –> tubule cell –> inst. fluid –> peritubular cap.

Front 64

What is the name of the symporter and anti-symporter in the PCT during reabsorption?

Back 64

- symporter: sodium-glucose symporter

- anti-porter: sodium-hydrogen anti-porter

Front 65

Describe the reabsorption mechanism of sodium and glucose

Back 65

1. Tubule Lumen –> PCT cell:

- Na+ and glucose (G) are pumped into PCT cell by Na+-G symporter on the brush border of PCT cell.

*Note: symporter is a paired mechanism – if Na+ can't get across, so will G (and vice versa)

2. PCT cell –> inst. fluid

- Inside the cell, Na+ is actively transported to the inter.fluid through Na+-K+ pump

- Inside the cell, G is passively transported to the inter. fluid through the glucose facilitated diffusion transporter

3. inst. fluid –> peri. cap.

- Na+ and G travel from inst. fluid and peri. cap. through diffusion

**NOTE: Na+ also travels paracellularly mainly for concentration gradient not electro; whereas, the transcellular mechanism described above is for electro purposes

Front 66

Where does the reabsorption of filtered glucose, amino acids, lactic acids, water-soluble vitamins and other nutrients take place? By what mechanism?

Back 66

- first half of PCT by Na+ symporter or anti-symporter

Front 67

Describe:

- reabsorption mechanism of bicarbonate, sodium and carbon dioxide

- secretion of H+

Back 67

-Reabsorption-

1. Tubule Lumen –> PCT cell:

- Na+ is transported inside the PCT cell through Na+-H+ antiporter

- CO2 gets into PCT through diffusion

2. PCT cell –> inst. fluid

- Na+ is actively transported to the inst. fluid through Na+-K+ pump

- Inside the cell, CO2 + H2O forms H2CO3, which catabolizes and breaks down into H+ and HCO3-

- HCO3- is passively transported to inst. fluid through HCO3- facilitated diffusion transporter

- H+ is transported back into the lumen through Na+-H+ antiporter

3. inst. fluid –> peri. cap.:

- Na+ and HCO3- both get across through simple diffusion into the peri. cap.

*4. peri. cap. –> PCT cell

- CO2 simply diffuses into PCT cell to contribute to the process that happens inside PCT cell

Front 68

What is the acid-base reaction that happens in the body? Where does it usually occur?

Back 68

Eq:

H2O + CO2 <–> H2CO3 <–> H+ + HCO3-

- an internal reaction @ PCT

Front 69

What is the equation to the neutralization of lactic acid?

Back 69

HLa + NaHCO3 <–> H2CO3 <–> H2O + CO2

Front 70

What are secreted during the reabsorption mechanism of bicarbonate, sodium and carbon dioxide in PCT?

Back 70

- H+

- NH4+ (ammonium)

- toxins

- drugs

Front 71

How can H+ in lumen fluid problematic?

Back 71

- H+ may bind with other ions and create unnecessary acids

- these acids may need to be neutralized through deriving reverse reaction such that we secrete H2O instead of acidic urine

Front 72

Describe the passive reabsorption in the late PCT. What substances are passively reabsorbed? (5)

Back 72

- all of Na+ movement draws H2O along via osmosis

- leaving H2O creates electrochemical gradient for other substances (ie: Cl- , K+ , Ca2+ , Mg2+ , urea) to move passively

- H2O follows reabsorbed solutes

Front 73

How does caffeine and alcohol affect reabsorption of Na+ in collecting duct?

Back 73

- inhibits reabsorption of Na+

- inc. GFR

- inc. urine output

Front 74

Define and provide hormones for: antidiuretic, diuretic

Define: diuresis and natriuresis

Back 74

- antidiuretic: water recoverer, dec. H2O output

ie: ADH, Aldo, A. II

- diuretic: water eliminator, inc. H2O output

ie: ANP

- diuresis: inc. urine volume

- natriuresis: excretion of large amt of Na+

Front 75

What hormone regulates Facultative H2O Reabsorption?

Back 75

- ADH by 10%

Front 76

Describe: ADH pathway when blood osmotic pressure is high (low blood volume)

Back 76

1. high BO/low BV stimulates hypothalamic osmoreceptors

2. osmoreceptors activate the neurosecretory cells that synthesize and release ADH

3. Nerve impulses liberate ADH from axon terminals in the post. pit. into the bloodstream

4. ADH target the ff. tissues:

a.) kidneys: retain more H2O through principal cells in collecting duct that open H2O channels for reabsorption which dec. urine output

b.) sweat glands: dec. H2O loss by perspiration from the skin

c.) arterioles: constrict which inc. BP

**Note: a.) and b.) act on BV; c.) acts on BP

Front 77

Describe: ADH pathway when blood osmotic pressure is low (high blood volume)

Back 77

1. Low BO/high BV inhibits hypothalamic osmoreceptors

2. Inhibition of osmoreceptors reduces or stops ADH secretion

Front 78

What is diabetes insipidus? What hormone causes diabetes insipidus?

Back 78

- Diabetes insipidus: large urine output from intense thirst even after drinking fluids

- caused by inhibition of ADH –> inc. urine output

Front 79

Describe ANP. What process is it responsible for? (Hint: I________ d_______)

Back 79

- inhibits water and sodium reabsorption in PCT and collecting duct

- suppresses section of Aldo and ADH

- responsible for immersion diuresis

Front 80

Describe what occurs in immersion diuresis.

Back 80

1. body immersed in H2O

2. causes narrowing of the blood vessels = vasoconstriction

3. vasoconstriction increases blood volume

4. inc. BV stretches atria and releases ANP which suppresses ADH

5. suppressed ADH causes increase in urine output

Front 81

How does the ureter transport urine? (3)

Back 81

- peristaltic waves

- hydrostatic pressure

- gravity

Front 82

True or false: there's a valve at the opening of the ureter into the bladder

Back 82

False – no anatomical valve

Front 83

How does the bladder prevent backflow of urine to ureters?

Back 83

- by compressing the ureteral openings

Front 84

Define micturition

Back 84

- urination or voiding

Front 85

Describe the involuntary and voluntary muscle contraction during micturition.

Back 85

Involuntary

- stretched bladder detected by stretch receptors

- spinal micturition reflex is triggered

- signals go to spinal cord

- spinal cord sends motor signals to bladder to contract and relax internal urethral sphincter

Voluntary

- external urethral sphincter relaxes

- urine is released

Front 86

True or false: Sensation of micturition reflex comes first than bladder fullness

Back 86

- False: bladder fullness sensation first then micturition reflex

Front 87

When do we learn to control micturition reflex? How do we control it throughout life?

Back 87

- learn control during childhood

- older children and adults may inhibit or initiate micturition voluntarily