BIOL 431 Unit 4 Lecture Exam

Urinary System & Fluid, Electrolyte & Acid-Base Homeostasis

kidney functions (6)

ion homeostasis

waste excretion

regulate blood pH

produce hormones

gluconeogenesis

regulate blood volume, pressure & osmolarity

3 main passageways of urinary tract

ureter

urinary bladder

urethra

nephron

structural & functional unit of kidney

2 main parts of nephron

renal corpuscle

renal tubule

2 parts of renal corpuscle

glomerulus

Bowman’s capsule

renal corpuscle function

produce filtrate

4 components of renal tubule

proximal convoluted tubule

loop of Henle

distal convoluted tubule

collecting duct

proximal convoluted tubule function

reabsorption of water, ions/electrolytes & all organic nutrients

loop of Henle components

ascending & descending limbs

loop of Henle function

sets up concentration gradient

descending limb function

reabsorption of water

ascending limb of the loop of Henle function

active transport; reabsorption of Na & Cl

distal convoluted tubule function

secrete ions, H+, drugs & toxins

variable reabsorption

collecting duct function

variable water reabsorption

secretion of Na, K, HCO3-, H+ based on needs

Types of nephrons

cortical nephron (80-85%)

juxtamedullary nephron (15-20%)

cortical nephron characteristics

short loops of Henle

surrounded by peritubular capillaries

juxtamedullary nephron characteristics

long loops of Henle

surrounded by vaso recta

establishes concentration gradient

juxtaglomerular apparatus (2 main cells & characteristic/function)

juxtaglomerular cells of affarent arteriole (modified smooth muscle)

macula dense cells of distal convoluted tubule (detect filtrate osmolarity for tubuloglomerular feedback)

juxtaglomerular apparatus function

regulates blood entry into glomerulus (to be filtered into filtrate)

glomerular filtration rate

rate at which blood is filtered to produce filtrate per time

reabsorption

movement of substances from filtrate back into the blood

secretion

movement of substances from blood into filtrate

excretion

urine flow rate

excretion formula

excretion = filtration - reabsorption + secretion

filtration membrane components

glomerular endothelial cells with fenestrations

basal lamina

podocytes with pedicels

glomerular endothelial cells with fenestration function

present passage of large substances (RBC, WBC, platelets)

basal lamina function

filters out large proteins

slit membrane between pedicels of podocyte function

prevents passage of medium sized proteins

filtration depends on (4)

size of substances

surface area available for exchange

diffusional distance

pressure gradient

4 pressure components for net filtration

glomerular blood hydrostatic pressure

blood colloid osmotic pressure

capsular hydrostatic pressure

filtrate colloid osmotic pressure

glomerular blood hydrostatic pressure & value

blood pressure pushing out (promotes filtration)

55 mmHg

blood colloid osmotic pressure & value

pulls fluid into blood

30 mmHg

Capsular hydrostatic pressure & value

pressure of fluid pressing against capsule

15 mmHg

filtrate colloid osmotic pressure & value

protein in suspension in filtrate taht causes osmotic pressure

0 mmHg

net filtration pressure equation & normal value

net filtration pressure = glomerular blood hydrostatic pressure - blood colloid osmotic pressure - capsular hydrostatic pressure

10 mmHg

glomerulonephritis/renal failure

damaged capillaries allow proteins into Bowman’s space

increases filtrate colloid osmotic pressure, increasing net filtration pressure (increased filtration & decreased blood colloid osmotic pressure)

can lead to edema

3 regulators of glomerular filtration rate

renal auto regulation

neural regulation

hormonal regulation

renal auto regulation (2 types)

myogenic mechanism

tubuloglomerular feedback

myogenic mechanism

quick regulation of glomerular filtration rate

stimulus: increased systemic blood pressure

response: vasoconstriction of affarent arteriole

effect: decreased glomerular filtration rate

tubuloglomerular feedback of GFR

slow regulation of glomerular filtration rate

stimulus: increased glomerular filtration rate

response: inhibit release of NO from juxtaglomerular cells

effect: vasoconstriction of affarent arteriole & decrease blood in glomerulus

neural regulation of GFR

important for detecting extreme drops in blood pressure

sympathetic division (NE) used to vasoconstriction affarent arteriole

decrease GFR & urine output

increase blood flow to other tissue

hormonal regulation of GFR

angiotensin II (vasoconstriction affarent arteriole, decrease GFR)

atrialnatriuretic peptide (ANP) (relaxes mesangial cells, increase surface area available for diffusion & increases GFR)

reabsorption routes

paracellular reabsorption

transcellular reabsorption

paracellular reabsorption

reabsorption between cells

limited by tight junctions between cells

transcellular reabsorption

absorption across cell via transport proteins

transport maximum

max amount of substances transported per time due to transporter efficiency

3 P’s of diabetes mellitus

polyuria

polyphagia

polydipsia

proximal convoluted tubule (urinary transport processes)

reabsorption (65% obligatory water reabsorption, glucose, amino acid & ions)

glucose, amino acid & water soluble vitamins reabsorption in proximal convoluted tubule

set up Na+/K+ concentration gradient with primary active transporter

use secondary active transport/symport to bring Na+ & substance into cell

use facilitated diffusion to move substance into blood

H+ secretion/HCO3- reabsorption in proximal convoluted tubule

establish Na+/K+ concentration gradient with primary active transporter

use secondary active transport/antiport to bring Na+ in & pump H+ out

use facilitated diffusion to move HCO3- into blood

water reabsorption in proximal convoluted tubule

moves into cell via aquaporin I

moves into cell via aquaporin I

paracellular water reabsorption

thin descending limb of loop of Henle (urine transport process)

water reabsorption via aquaporin I

paracellular water reabsorption

thick ascending limb of loop of Henle (urine transport process)

impermeable to water

active reabsorption of Na+ & Cl- via NKCC (reabsorbs Na+ & 2 Cl-; secrete K+)

countercurrent multiplication

sets up concentration gradient at loop of Henle

countercurrent exchange

maintains established concentration gradient

late distal convoluted tubule/collecting duct (urine transport process); fxn & 2 cells it takes place at

fine tunes filtrate based on bodily need

principal cell & intercalated cell

principal cell (urine transport process)

reabsorbs Na+/secrete K+ (regulated by aldosterone)

water reabsorption (facultative water reabsorption; regulated by ADH)

intercalated cell (urine transport process)

reabsorbs HCO3- & secretes H+

regulated by acid/base balance

hormonal regulation (3 main hormones/process)

antidiuretic hormone (ADH)

renin angiotensin aldosterone (RAA) cascade

atrial natriuretic peptide

Antidiuretic hormone (reflex arc)

stimulus: increased blood osmolarity

receptor: osmoreceptor (hypothalamus)

control center: released by posterior pituitary gland

effector: ADH inserts aquaporin II in principal cells

effect: increased water reabsorption, decreased blood osmolarity & decreased urine output

Renin angiotensin aldosterone cascade

stimulus: decreased blood volume & blood pressure

receptor: juxtaglomerular apparatus (kidneys; produce renin); renin converts angiotensinogen (from liver) into angiotensin I ; lungs produce Angiotensin converting enzyme (ACE) to convert angiotensin I to angiotensin II

angiotensin effect: vasoconstriction of affarent arteriole (decreased GFR, decreased urine output, increased blood volume); increased systemic vasoconstriction, increased Na+, Cl- & water reabsorption; increased thirst; stimulate adrenal cortex to produce aldosterone

aldosterone effect: increased Na+ reabsorption & K+ secretion (increased water reabsorption & blood volume)

atrial natriuretic peptide (stimulus & effect)

stimulus: increased blood volume

atria detects & secretes atrial natriuretic peptide

decreased Na+ reabsorption, decreased water reabsorption, decreased aldosterone & ADH secretion, increased filtration rate

3 factors of medullary concentration gradient

countercurrent multiplication

urea recycling

countercurrent exchange

countercurrent exchange established by what & its specifics

established by loop of Henle

descending limb: obligatory water reabsorption

ascending limb: active Na+ & Cl- reabsorption

urea recycling

urea produced by deamination of proteins

collecting duct permeable to urea & concentrates in medulla

countercurrent exchange established by what & its specifics

vasa recta

increased blood concentration along gradient

urinalysis & its factors

volume (\~1 mL/min)

transparency (typically clear)

specific gravity (1.001-1.035)

pH (4.6-8; varies by diet)

color (changes with dilution/concentration)

odor (can vary with diet)

urination/micturition reflex (stimulus, receptor, control center, effectors & effect)

stimulus: stretch of urinary bladder (200-400 mL)

receptor: stretch receptor

control center: micturition center @ spinal cord

effectors: parasympathetic nervous system

effect: contraction of detrusor muscle, relaxation of internal & urethral sphincter

osmolarity of kidney from cortex to medulla

300 mOSM

600 mOSM

900 mOSM

1200 mOSM

how does filtrate osmolarity change as it descends from cortex into medulla

descending limb of loop of Henle; water reabsorption (from 300 mOSM to 1200 mOSM)

how does filtrate osmolarity change as it ascends from medulla into cortex

ascending limb of loop of Henle; active Na/Cl reabsorption & impermeable to H2O

makes filtrate 200mOSM less than surrounding interstitial fluid (1200 mOSM to 100 mOSM)

filtrate osmolarity in distal convoluted tubule

100 mOSM

to produce hypotonic urine

low ADH

decreased water reabsorption in collecting duct

urine: 100 mOSM

to produce hypertonic urine

high ADH

aquaporin II inserted into principal cells of collecting duct

increased water reabsorption

urine: 1200 mOSM

total body mass made up of fluids

55-60%

2 main categories of bodily fluids

intracellular fluid (2/3)

extracellular fluid (1/3)

extracellular fluid made up of

interstitial fluid (80%)

blood plasma (20%)

interstitial fluid and plasma separated by

capillary endothelial cells

intracellular fluid & interstitial fluid separated by

plasma membrane

water balance equation

water gain = water loss

water gain (\*main point of regulation)

ingested liquids\*

ingested foods

metabolic waters

water loss (\*main point of regulation)

kidneys (via urine) \*

skin (sweat)

lungs (breathing)

GI tract (fecal formation)

dehydration (causes, overall effect & symptoms)

water loss > water gain

causes: excessive perspiration, inadequate water intake, alcohol, vomit/diarrhea, diabetes mellitus, diabetes insipidus

overall effects: increased blood osmolarity & decreased blood volume

symptoms: sunken eyes/cheeks, decreased skin tumor, sunken fontanelle, few/no tears, dry mouth/tongue, sunken abdomen

over hydration (causes, overall effects & symptoms)

water gain > water loss

causes: excessive drinking of hypotonic solution/water, inability to eliminate water, endocrine disorder

overall effect: decreased blood osmolarity & increased blood volume

symptoms: water intoxication

increased osmolarity will result in what corrections (and their effects)

increased thirst

increased ADH (increases aquaporin II on collecting duct = increased water reabsorption)

decreased blood volume will result in what corrections (and their effects)

decreased atrial natriuretic peptide (increased sodium reabsorption)

increased renin angiotensin aldosterone (increased angiotensin II leads to increased thirst, increased sodium reabsorption, increased aldosterone & decreased GFR)

decreased blood osmolarity will leads to what corrections (and their effects)

decreased thirst

decreased ADH (decreased water reabsorption)

increased blood volume will lead to what corrections (and their effects)

increased atrial natriuretic peptide (decreased sodium reabsorption)

decreased angiotensin aldosterone (decreased thirst, decreased sodium reabsorption, decreased aldosterone & increased GFR)

important electrolytes

sodium

potassium

chloride

calcium

phosphate

magnesium

sodium (function, in excess, depleted & regulated by)

function: carry action potential, fluid & electrolyte balance

in excess: hypernatremia

depleted: hyponatremia

regulated by: ADH, ANP & RAA

potassium (function, excess, depleted & regulated by)

function: establish resting membrane potential & repolarization of action potentials

in excess: hyperkalemia

depleted: hypokalemia

regulated by: aldosterone

chloride (function, excess, depleted & regulated by)

function: anion balance & HCl production

in excess: hyperchloremia

depleted: hypochloremia

regulated by: ADH

calcium (function, excess, depleted & regulated by)

function: bone & teeth formation, blood clotting, neutrotransmitter release & muscle contraction

in excess: hypercalcemia

depleted: hypocalcemia

regulated by: calcitonin, parathyroid hormone & calcitriol

phosphate (function, excess, depleted & regulated by)

function: bone & teeth formation, buffer

in excess: hyperphosphatemia

depleted: hypophosphatemia

regulated by: calcitonin & parathyroid hormone

magnesium (function, excess, depleted & regulated by)

function: bone formation, cofactor for enzymes

in excess: hypermangesemia

depleted: hypomagnesemia

regulated by: N/A

main extracellular electrolytes

Na+, Ca2+, Cl-

main intracellular electrolytes

K+, Mg2+, HPO42-

normal blood pH

7\.35-7.45

more acidic blood found in

systemic veins (increased \[CO2\])

more basic blood found in

systemic arteries (decreased \[CO2\])