physiology final Flashcards
What is the job of the kidneys?
maintain the constancy of the body’s internal environment
How do they accomplish this?
By regulating the volume and composition of extracellular fluids
What do they use to excrete metabolic end products?
Nephrons
What else are the kidneys involved with?
regulation of the total amount of many important substances in the extracellular matrix.
What are the 7 main functions of the kidneys?
1- regulation of the concentration of numerous ions. 2- excretion of organic compounds. 3- fluid balance. 4- acid-base balance. 5- blood pressure regulation. 6- erythrocyte volume regulation. 7- Vitamin D activation
How do the kidneys accomplish #1? (from previous ?)
excretion or preservation of Na, Cl, K, Ca, PO4 - balance their intake, production or excretion through other routes
How is #2 accomplished?
1) elimination of substances like urea and creatinine in amounts equaling their production rates. 2)elimination of drugs, FO, and toxins
3?
1)regulate water. 2) regulate osmotic pressure of EC fluids. 3) produce urine
4?
excretion of H+ or HCO2 as needed
5
renin-angiotensin system and renal-body fluid balance system
6>
through formation and release of erythropoetin
7?
vitamin D hydroxylation to render it useful.
How much more salt than water do humans typically consume each day?
20-25%
How is that excess salt/water disposed of?
Urine
What sensors determine how much is to be excreted?
water volume sensors, salt sensors, osmolality sensors,
How do these sensors instruct the kidneys on what to do?
via hormones.
Where does all the action in the kidney take place?
Nephrons
What is a nephron encased in?
a maze of peritubular capillaries
What are the components of a nephron?
1) Glomerular capsule, 2) PCT, 3) loop of Henle, 4) DCT, 5) collecting duct
What are the components of the vasculature of a nephron?
1) intralobular artery. 2) afferent arteriole 3) glomerulus 4) efferent arteriole 5) peritubular capillaries 6) venule and intralobular vein
What are the 3 versions of a nephron?
1) superficial. 2) mid-cortical. 3) juxtamedullary
What 3 activities do kidneys engage in?
1) filtration 2) reabsorption 3) secretion
Where is the bulk of the work done?
in glomeruli and PCTs
What remains in the final end of the tubules?
urine
How does blood enter the kidney and nephron?
through Renal artery
What does the blood return to circulation through?
renal vein
The nephron is said to “clear” what?
the blood of unwanted substances - removes unwanted agents from the plasma
What is clearance?
the amount of plasma cleared of a given substance
How can glomerular filtration rate be measured?
by looking at the clearance of something that is freely filtered and not reabsorbed at all.
How can you measure cortical perfusion?
by looking at the clearance of something that is secreted from the peritubular capillaries into the nephric tubules
What establishes a natural filtration and absorption process?
normal blood pressure and osmotic drives
How does blood pressure move water?
creates a hydraulic “push”
How does osmotic drive move water?
osmotically active solutions “draw” water toward them.
What happens to pressure through the nephron?
steadily falls
What are two critical locations for pressure ?
1) Glomerular capillaries. 2) peritubular capillaries
What happens in glomerular capillaries?
High BP like arteriole end of a system capillary
What happens in the peritubular capillaries?
Low BP like venule end of systemic capillary
What do high pressure beds create?
net outward flow (loss)
What do low pressure beds create?
net inward flow (gain)
What order does fluid flow through PCT and Peritubular cap beds?
PCT first, then into peritubular.
How does osmolality and glomerulus set up return of water?
glomerulus loses fluid but keeps cells and proteins, peritubular caps are very osmotically active - draws fluid back from nephric tubules.
Does water resorption become easy or difficult?
Increasingly difficult.
What is glomerulonephritis?
disorder of renal glomeruli - collection of diseases that effect the glomerular membrane.
What is the most common subtype?
inflammatory processes - diffuse proliferative form
What is the most common cause?
Post-streptococcal glomerulonephritis
What are the clinical features?
Oliguria (decreased urine output. Edema. HTN. Foamy urine. Brown urine
Lab findings?
Glomerular caps appear damaged. Hematuria. Proteinuria. Immunofluorescence shows granular deposits.
What does chronic form lead to?
renal failure - steady loss of glomeruli
What does renal function begin with?
production of glomerular filtrate
What is the overall strategy in the urinary system?
filter huge amounts of blood and recover nearly all of the good stuff.
How much renal blood flow is there?
1000 - 1200 ml/min to kidneys
How much cardiac output does this equal?
20-25%
What is this known as?
The renal fraction
What is glomerular filtrate?
the amount of plasma “lost” from blood volume when delivered to glomeruli
how much is produced from glomeruli filtation?
160 - 180 l/day (2x ones body weight)
How much is recovered after glomeruli filtration?
1 -2 l/day leaves as urine. = recovery rate of 99%
What type of membrane is on glomeruli?
consists of type 2 capillaries and a visceral bowmans capsule covering of podocytes`
describe the permeability of glomeruli capillary beds?
several hundred times more permeable than the typical type 1 kind
What does this allow for?
Substantial filtering
What determines what passes through?
size, molecular shape and charge.
what does the endothelium block?
formed elements fenestrations much smaller than platelets
What does the basement membrane block?
proteins negatively charges basement membrane materials repel negatively charged plasma proteins
what are slit pores?
space between pedicels that allows the remains to flow through.
What is glomerular filtration a function of?
pressure across the glomerular membrane.
what is the capillary blood pressure?
60 mmHg = outward force
What is the colloidal osmotic pressure?
32 mmHg = inward force
What is the capsular pressure of filtrate?
18 mmHg = inward, backward force
is capillary force higher or lower than systemic capillary blood pressure?
very high
When does colloidal osmotic pressure rise?
as filtration continues
What is the net driving force?
adding up forces 60 + (-)32 + (-)18 = 10 mmHg OUT
what is total filtration?
NDF x Kf (filtration coefficient) = GFR
what is the GFR
glomerular filtration rate
What would the GFR be for the above info?
12.5 ml/min/mmHg X 10 mmHg = 125 ml/min
What would the GFR be for an entire day?
125 ml/min X 60 min X 24 hr = 180 liters/day
What would affect this total?
increased or decreased glomerular pressure.
How do fluctuations in BP alter GFR?
They probably don’t alter it much. (unless it’s an extremely dramatic change)
What is the autoregulation range?
when MAP is between 80 and 180 mmHg
What kind of innervation is significant to the kidneys?
Sympathetic
Is it more extensive to afferent or efferent?
afferent
What substances can cause renal arterial vasoconstriction?
Angiotensin 1. vasopressin/ADH, epi, norepi, thromboxane A2, endothelin
which cause vasodilation?
Acetylcholine, ANP, dopamine, histamine, nitric oxide, some prostaglandins
What does an increase or decrease in plasma colloidal osmotic pressure cause?
in hypoproteinemia it causes edema in systemic capillaries
What happens with an increase of decrease in bowmans capsule pressure?
tubule obstructions or severe kidney stones will cause fluid to back up and increase pressure
what happens with an increase or decrease in glomerular capillary permeability?
thickening or plugging of membrane pores
What happens with an increase or decrease in glomerular capillary total surface area?
glomerular destruction will decrease available membranes for GFR. (seen with nephric disease that remove functional tissue.
What is final Glomerular filtrate normally similar to?
Plasma minus its proteins.
What is glomerulonephritis?
a disorder of renal glomeruli usually due to inflammatory processes, most commonly as a diffuse proliferative form
What does post-streptococcal glomerulonephritis result in?
deposition of circulating immune complexes that further attract neutrophils
What happens to the G membrane?
becomes clogged and inflammatory reaction make it worse
What are the clinical features?
oligouria due to loss of filtration. Edema and HTN due to fluid accumulation
What are the lab findings?
G capillaries appear damaged -> hematuria. Foaming of urine from proteinuria. Thickening of G membrane
Is there treatment?
yes. Mild can heal on own. Eliminate HTN. dialysis
What is Fanconi’s syndrome?
a collection of very uncommon diseases that involve the kidneys
What do all forms affect?
The behavior of the nephron, especially PCT
What does this result in?
deficient renal tubular excretion
What are common sources of this problem?
alteration in transporters. Disturbances in cellular energy metabolism. Changes in permeability
Clinical signs?
in children: polydipsia, malnutrition, infection. Adults: pain in weight bearing joints, dehydration
Lab findings?
aminoaciduria, cystinuria, glycosuria, phosphaturia. Hypokalemia, metabolic acidosis, hypercalciuria
What is the principle activity in the nephric tubules?
recovery of most filtrate.
What is the primary function of the rest of the nephron?
reabsorption of glomerular filtrate
What are the 4 mechanisms of tubule exchange?
1) some substances actively resorbed. 2) some actively secreted. 3) some passively resorbed 4) some passively secreted
What is the flow rate of G filtrate suggestive of?
where most of the work is done.
Where is flow rate highest?
PCT
2nd highest?
Loop of Henle
3rd highest?
DCT
4th highest?
collecting duct
What does flow rate begin and end at within the PCT?
125 ml/min and falls to 45 ml/min
What does flow rate fall to at end of DCT?
15 ml/min
What does flow rate fall to at end of CD?
0.7 ml/min
How much urine does this work result in each day?
1 l/day. (0.7 X 60 X 24)
How much nephric flow takes place in PCT?
2/3 of all flow. (70% of water resorption)
What 3 kinds of basic solutes does the kidney process in the tubules?
1) Nutritionally important substances. 2) ions/electrolytes 3) metabolic end-products
What does the recovery of specific filtered solutes reveal?
reveals what part of the nephron does what.
How are nutritionally important solutes absorbed?
to completion
What kind of transport is the basic mechanism of glucose?
secondary active transport
What is co-transport of Na+ and GLU made possible by?
Na+/K+ exchange pump (requires ATP)
How does GLU moves across the basal side into the ECM?
facilitated diffusion. (with GLUT2 protein)
What does GLU transportation require?
Energy
What is total GLU absorption a function of?
The number of transporters. (which is a function of surface area)
How much is normally absorbed?
All of it. Absorbed to completion
What is TMG?
total glucose that can be absorbed… tubular transport max
What does this represent?
The number of funtioning nephrons.
What is the estimated amount?
350 mg/min
What is this AKA?
tubular absorption capacity.
What does this mean?
tubules can reabsorb 350 mg of glucose every minutes
Where is it done?
PCT
What is the renal threshold of glucose?
where glucose might appear in urine
How can renal threshold be calculated?
by using TMG (375..round up from 350?). a GFR of 125. and plasma glucose concentration of 100 mg/100ml = (375/1)x(1min/125ml)x(100/100) = 300mg/100ml of plasma.
Is this quantity higher or lower than normal plasma glucose levels?
higher.
What does that mean?
no glucose should be in the urine.
What does this say about the kidneys?
That they are not meant to control the concentration of blood glucose.
What happens to the amount of GLU resorbed compared to filtered load?
they match up…. to a point
When will excretion happen?
When the TMG is reached.
What is the actual renal threshold for glucose?
180 - 200 mg/dl
What is this number due to?
splay or bending in the theoretical curve.
What does splay represent?
nephron variability
What is there a specific transporter for?
each kind of sugar and for each kind of facilitated diffusion on the basal surface
Where are larger carbohydrates broken down?
PCT
What enzyme does this?
surface amylase. (and maltase)
What are they broken down to?
simple sugars
How are some large carbohydrates brought across the tubule wall, and what is their fate?
Pinocytosis.. lysosomal destruction
How are amino acids moved across?
similar to simple sugars (and glucose). By secondary active transport.
Where are larger peptides broken down?
PCT.
What breaks them down?
surface peptidases
What are they broken down to?
to amino acids.
What are all the previous substances considered to be?
nutritionally important.
Where have all of the previous substances been reabsorbed, and to what extent?
in the PCT and to completion
When do the rest of the tubules become important?
When processing substances that the PCT did not complete
What is the average intake of salt per day?
8-15 g/day
What is the most common cation of the ECM?
Na+
Why are there multiple methods for Na+?
because it is linked to the cotransport of many solutes.
Wherre does the Na+/K+ exchange pump move Na+ to?
exterior of the cell on the basal surface.
Why does Cl- generally follow Na+?
for electrogenic reasons.
How much Na+ and Cl- are resorbed in the PCT?
65 percent
Where else, and how much, are they resorbed?
25% in asc. Limb of loop of henle. 5% in DCT. 5% in CD.
What does the amount of resorption equal?
the amount of salt intake (until there is excess)
How can reabsorption be INDIRECTLY controlled?
by body osmolality
What hormone controls this?
aldosterone
What does aldosterone work through to achieve this?
BP regulatory scheme.
What does increase aldosterone lead to?
increased Na+ resorption
What does decreased aldosterone lead to?
decreased Na+ resorption
How does aldosterone work?
it works on DCTs by altering the number of Na+/K+ exchange pumps and their activity
What kind of regulation is this?
Distal nephron function
What else does Na+ (and Cl-) effect?
the macula densa
When does it effect the macula densa?
as filtrate passes through the DCT (the densa cells communicate with JG cells)
What does increased Na+ do to JG cells?
stimulates them to decrease secretion of renin (and angiotensin) and decrease aldosterone
What does decreased Na+ do to JG cells?
stimulates them to increase secretion of renin (and angiotensin) and increase aldosterone
What does changing Na+ intake do? (big picture)
alter water retention, lead to changes in BP, and CV changes that will lead to altering Na+ retention
What are the kidneys the prime regulators of?
body sodium (and chloride) content
What is ANF?
atrial natriuretic factor (or peptide… ANP)
What does it do?
its a hormone from the right atrium and has a potent effect on kidneys. Acts as a diuretic.
When is it released?
with atrial stretch.
What does a release of ANF cause?
increased production of urine and thereby decrease blood volume
What else does this hormone cause?
decreased renin release. Decreased aldosterone secretion
What is potassium?
a potentially dangerous cation
Where is K+ processed?
It is variably processed by nephric tubules.
What much match K+ intake?
urinary excretion
Where is 98% of K+ found?
inside cells (internal K+ balance)
What factors effect K+ balance within cells?
many factors: notably, stimulants and acid/base chemistry of the ECF
What factors increase K+ levels in the ECF? And what do they lead to?
hyperosmolarity, cell lysis, exercise, acidosis. They lead to Hyperkalemia
What factors decrease K+ levels in the ECF? What does this lead to?
Hypo-osmolarity, insulin, alkalosis. Leads to Hypokalemia
What are two kinds of alpha and beta adrenergic agonists?
norepi and epi.
How do norepi and epi have variable effects on cells?
they enhance or inhibit the Na+/K+ exchange pump.
What do some alpha antagonists cause?
decrease in plasma K+ levels
What do some beta antagonists cause?
increase in plasma K+ levels (propanolol)
How is processing of K+ accomplished?
By way of active pumps and simple channels.
How much resorption of K+ is done in PCT?
70 percent
Where else is it resorbed and how much?
20% in loops of henle, and 10% in DCT (and upper CD)
What mechanism for K+ resorption is used in PCT?
passive. With NaCl and water
Where does the critical action of resorption of K+ take place?
DCT
What does the primary mechanism for K+ resorption depend on?
the DCT cell sub-type.
What are the two sub-types?
Alpha-intercalated and principle.
What determines which sub-type is used?
body needs. And electrochemical gradient that drives K+
which sub-type is used with decreased K+ intake?
Resorption = alpha-intercalated cells
which sub-type is used with increased K+ intake?
Secretion = principle cells
Which is the main action?
principle cells
What factors affect the principle cells?
Dietary K+, Aldosterone, Acid-base, flow rate, luminal anions
What does this insure?
that K+ levels do not rise too high in the blood
What does increase aldosterone cause with K+? and how?
decrease K+. by minimizing secretions in DCT
What is the prime regulator of the body’s K+ content?
the kidneys, duh
How much more H2O does the average human consume than is needed?
20-25%
What is the average intake of H2O per day?
2.5 Liters
Which is tougher to manage -> H2O disposal, or H2O retentions?
Retention
How much H2O is resorbed in the PCT?
70%
Where else is H2O resorbed?
15% in loops, 5% in DCT, 10% in CD
How does the nephron adjust body water levels?
By producing either a dilute or concentrated urine
What kind of urine does excess body water lead to?
dilute urine… increased urine volume
What kind of urine does lack of body water lead to?
concentrated urine… decreased urine volume.
What is osmolality?
measure of the tendency of a solution to induce osmosis.
What is the average body fluid osmolality?
300 mOsm… body/blood osmolality
Which portion of the tubules is relatively impermeable to water?
CD
What is the average osmolality in the PCT?
300 mOsm
What is the average osmolality in the DCT?
100 mOsm
What about in the CD?
can fall to 50 mOsm (very dilute, but not 0 because of regular waste)
What does this mean?
Whatever is left in the DCT will probably flow out with urine
What has to happen to the CDs to maintain renal concentration?
they need to become more permeable to give water a reason to want to leave.
Where does the bulk of water recovery happen?
in the PCT and into peritubular capillaries.
What do the medullar peritubular capillaries recover?
The resorbed water from the CD
How many nephrons are JM?
15%
Do animals with high urine concentration ability have more or less JM nephrons?
much higher…. i.e. hopping mouse has 85% JM
What is related to renal concentration ability in animals?
loop number and length.
What are counter-current systems?
pipes that double back on itself. - they have special properties.
What do counter-current systems involve?
allowing a tubule to communicate with itself.
How is this communication accomplished?
through the loops of henle!
In kidneys, instead of heat (his analogy for CC systems) what is magnified?
osmolality
What about loops of henle make this possible? (specific feature)
thick ascending segments and counter-current flow
What is possible through the thick ascending loops?
actively pumping NaCl into the interstitium
Step 1:
filtrate goes through thick ascending loops and pumps NaCl out to interstitium (CC multiplier)
Step 2:
after increase in NaCl , new filtrate enters descending limb - H2O leaves to saline interstitium = further concentrates tubule
Step 3:
Subsequent filtrate reach thick asc loops, NaCl pumping out still, Solute REENTERS desc limb = further concentrating it
Step 4:
Subsequent filtrate in thin limb has vigorous H2O removal (hypertonicity). = Thin limbs equilibrate with interstitium
Step 5
Dilute tubular fluid passes to distal nephron. Exposed to hypertonic medullary interstitium. = Powerful osmotic drive for H2O to leave.
Step 6:
ADH present. H2O leaves to interstitium = concentrated urine in tube. Antidiuresis now makes concentrated urine.
What determines the degree of hypertonic medullary interstitium (high osmolality)?
the length of the loops
What is the saltiest place in the human body?
Medullay pyramids.
What important structures insure all of this happens?
The vasculature in the area.
What do vasa recta do?
serve to preserve and accentuate the effect. Also recover NaCl from filtrate
Step 1:
blood descends in medullary interstitium. H2O leaves and NaCl enters = Increase in osmolality of vasa recta blood.
Step 2:
Blood returns from deeper medulla is high concentrated and loses its NaCl to the upper interstitium and H2O enters.
What do ascending vasa recta do?
Serve to capture resorbed H2O from CDs
Where do they send this?
to the body
Why is ADH critical?
changes the permeability of the CDs.
What does an increase in ADH cause?
water recovery ? increased urine
What does decreased ADH cause?
water loss ? decreased urine
Where is ADH synthesized?
in neuro-secretory cells of the paraventricular nuclei and supraoptic nuclei of the hypothalamus
Where do they project axons to?
posterior pituitary
Where does ADH land on the kidneys?
receptors (V2) of the CD
What does this cause?
insertion of reserve pools of cytoplasmic aquaporin-2 proteins.
What is increased when this happens?
increases permeability of these cells. Also increases synthesis of aquaporins
What do the membranes of epithelial cells lack in tubules that are relatively impermeable to water?
aquaporins.
What is diabetes insipidus?
failure of ADH
What does it cause?
excessive excretion of large amounts of dilute urine. Excessive thirst.
What are the causes of diabetes insipidus?
insufficient secretion of ADH, inheritance of mutated gene for ADH V2 r/c, inheritance of mutated gene for aquaporin-2
How much filtrate could be lost each day with DI?
20 liters
What is pyelonephritis?
an infection of the kidneys; more common in adult females.
What causes pyelonephritis?
bacteria condition of the renal medullary pyramids originating from reflux in urine from bladder.
What are the acute symptoms of pyelonephritis?
fever. Burning urine. Aching ab pain.
What kind of urine do you find in pyelonephritis?
dilute urine…
Why?
Invasion of bacteria in the medullary pyramids lessen their ability to produce hypertonic osmolality.
What is urine concentration and diuresis determined by?
changes in body chemistry
What is water diuresis?
common experience involving increased urine output due to water causing the posterior pituitary to lessen the amount of secreted ADH.
What is water intoxication?
When water intake exceeds the bodies ability to expel it
What is the normal max diuresis?
About 16 ml/min.
What is considered too much intake of water?
when intake exceeds a sustained rate of 1 l/hour.
What can happen at this point?
brain edema ? convulsions, death
What kind of urine is produced with diabetes mellitus?
sweet urine!
Why is it sweet?
because the Tmg of the PCTs is exceeded.
How much urine is produced in diabetes mellitus?
a large amount due to osmotic load on the nephrons. (known as osmotic diuresis)
What is hydrogen disposed as?
as an acid
What 3 mechanisms manage hydrogen concentration?
Blood plasma buffers. Respiratory ventilation. Renal excretion of an acid or alkaline urine.
How does blood plasma buffers manage H concentration?
rapidly- taking seconds to accomplish , with minimal gain due to temporary binding of hydrogen
How does respiratory ventilation manage [H]?
Slower taking minutes to an hour with higher gain due to change in plasma chemistry (as HCO3)
How does renal excretion of an acid or alkaline urine manage [H]?
slow, taking hours to days with the highest gain since it results in true elimination from body.
How do the kidneys regulate [H+]?
by increasing or decreasing [HCO3]
Where is filtered bicarbonate primarily resorbed?
in the PCT
Where is resorption of bicarbonate finished?
in the distal nephron
Where is the final acidity completed?
in the distal tubules. Therefore it is the most important determinant in the final pH of the urine.
What actively secretes H+?
the nephron
How is H+ ultimately lost?
as H2O in urine
Is urine normal acidic or basic? And why?
slightly acidic because all the HCO3- is resorbed, leaving the urine with a lower pH
What is the normal pH of urine?
6.5 - 7 can vary
What is the range of pH urine could be within?
4.5 - 8.5
Why won’t it fall below 4.5?
That is the level when active secretion is exceeded.
What are acids and acidifying salts as diuretics?
some of these supply nephrons with a filtered acid load that counteracts the ability to secrete H+
What does this lead to?
ability to exchange Na+ is somewhat compromised (also, with increased Na+ comes increased H2O loss)
What is acidosis?
increase in H+ (decreased pH)
What does this cause?
as H+ rises it exceeds available HCO3- to titrate against ? acid urine
What is alkalosis?
increasesd HCO3-
What does it lead to?
as HCO3- rises it exceeds available H+ secretions ? alkaline urine
What 2 chemical systems handle the buffering of H+ in distal nephron?
phosphate buffer. Ammonium buffer.
What is the phosphate buffer?
HPO4-2 + H+ ? H2PO4-
What is the ammonium buffer?
NH3 + H+ ? NH4+
Where is ammonia produced?
from glutamine in the nephron
Why does urine sometimes smell like ammonia?
ammonia ion being converted back to ammonia when exposed to air (has to sit in open air for a long time)
What is urea?
a common waste molecule from the end-stage of protein catabolism.
Why does urea use the aquaporin channel?
To diffuse in the collecting ducts.
How quickly does urea move through the tubule cells?
much slower than water…. so it tends to just pass out with urine.
What is BUN?
Blood-urea-nitrogen. Measure of urea in blood. (higher than normal shows abnormal renal function)
Where is calcium found?
extracellular
Where is phosphate found?
intracellular fluid
How is calcium balanced?
With net loss from body.
What normally regulates calcium?
parathormone in the parathyroid gland.
What does calcitonin make the kidneys do?
excrete Ca2+
What do the kidneys have a natural tendency to do with calcium and phosphate?
keep (reabsorb) PO4-2 and excrete Ca+2
What is this modified by?
parathormone in the parathyroid gland.
What does regular PTH secretion lead to?
kidney keeps Ca2+ and lets PO4-2 go
What is the net effect of this?
increase serum Ca2+
What do all forms of Fanconi’s syndrome affect?
the normal behavior of the nephron
Which portion of the nephron is mostly affected?
PCT
What do the diseases that produce this result in?
abnormal renal tubular excretion (as electrolytes and nutrients spill into the urine)
What are the clinical signs and symptoms of Fanconis in children?
children: polydipsia, malnutrition, susceptibility to infection.
What are the clinical signs and symptoms of Fanconis in adults?
pain on weight-bearing joints, dehydration, polyuria.
If left untreated what might this lead to?
Muscle-wasting and death
What does pyelonephritis do to the medulla?
fould the ability of the ascending loops to do their job.
What is the result?
failure of the renal concentration mechanism. ? large volume dilute urine.
What does hemostatic maintenance of the ICF involve?
stabilized with appropriate nutrient delivery, waste removal, and ionic/osmotic balance.
What surrounds this compartment?
ECM, which also has to be maintained.
What maintains the ECF?
The blood
What is the average percent of body fluid in adults?
60%
What is it in infants?
80%
What about in the elderly?
40-50%
Which compartment decreases with age?
interstitial compartment
Which compartments remain fairly stable throughout life?
Plasma, and intercellular compartments.
Why do women have less water than males in their body?
Because they have more fat which is low in water.
Where does our water intake come from? And how much from each?
Drink = 50%, food = 35%, oxidation = 15%
How does water exit our body? And how much from each?
Urine = 60%, sweat & ventilation = 35%, stool/feces = 5%
What do the kidneys do in response to diarrhea?
conserve fluid as to balance the body.
what kind of urine would the distilled water group produce?
large volume dilute
What kind of urine would the isotonic solution group produce?
balanced isotonic urine
What kind of urine would the 10% salt water group produce?
decreased volume, concentrated urine.
What does the body do when the osmolality of blood rises or falls?
manages concentrations of salt and water to correct the change
What hemostatic mechanisms are activated when osmolality of blood rises?
Secretion of ADH. Thirst. Lesser players
What are the lesser players?
decrease renin ? decrease aldosterone ? decrease Na+ reabsorption; and decrease ANF ? decrease renal flow.
How is ADH released?
neurons from the supra optic nuclei emanate from hypothalamus to post. Pituitary
What are these neuronal cell bodies sensitive to?
osmolality of blood.
What happens to these neurons when osmolality of blood rises?
secrete ADH. ADH enters blood. Goes to renal CDs. Lands on V2 r/c. Cells add aquaporin. ? promotes H2O reabsorption into vasa recta.
What happens to the osmolality of urine when the above takes place?
it goes up.
what happens to the osmolality of the blood at this point?
Returns to normal.
What else do these neurons stimulate?
the thirst center
What is the blood volume and systemic BP like when osmolality of blood is rising?
both are low.
THUS ?
increase osmolality ? increase ADH secretion ? water retention (anti-diuresis)
the opposite is also true ?
decrease osmolality ? decrease ADH ? water loss (diuresis)
What can a water deficit be caused by?
excessive sweating or osmotic diuresis.
What might this result in?
fluid shifting from intracellular to extracellular compartment
What can water excess be caused by?
Excessive drinking, excessive ADH
What might this result in?
fluid shifting from extracellular to intracellular compartment.
What homeostatic mechanisms are activated when blood volume falls?
secrete ADH, secrete renin angiotensin and aldosterone, decrease ANF ? decrease renal flow.
What else will a fall in blood volume cause?
fall in BP
What 2 things will a rise in renin cause?
increase angiotensin 1&2 ? systemic constriction ? increase BP. AND increase aldosterone ? increae Na+ reabsorption in distal nephron ? decrease fluid loss
THUS ?
decrease blood volume ? increase renin/angiotensin & aldosterone ? increae BP and decrease water loss
Salt deficit from vomiting, diarrhea, excessive sweating results in what?
fluid shifting from extracellular to intracellular compartment.
Salt excess from excessive intake can result in?
fluid shifting from intracellular to extracellular compartment
What is incontinence?
The failure to store urine when desired
What is incontinence a disorder of?
involving a lack of control of the urinary bladder
When does renal function end?
when there is an accumulation of urine in the bladder. (after having left the renal calyces, pelvis, and ureters.
What kind of reflex is micturation?
autonomic spinal cord reflex though it can be inhibited.
What happens to pressure as urine accumulates in the bladder?
internal pressure rises
When do ramp signals begin in the bladder?
When fluid reaches 30-50 ml. - rises rapidly when over 300-400 ml
When does active signaling begin?
100 ml, but very strong by 300 ml
What is the secondary nerve associated with micturation?
pudendal n
What does the pudendal do during micturation?
inhibits internal urethral sphincter.
What neurophysiological or anatomical factors can cause incontinence?
destruction of sensory fibers to CNS. Crush injury to sacral region of spinal cord. Injury to region above sacral region.
