Lecture 10: Kidneys Flashcards
1) What is the main job of the kidneys? What is this important in?
2) They make up ___% of body weight but receive ___% of cardiac output
1) Help to regulate the extracellular fluid and keep it stable; homeostasis
2) 1%; 22%
1) Give 3 reasons why the kidneys are important to homeostasis
2) What innervates the kidneys? What happens if this is activated?
1) Stable fluid volume, electrolyte composition, solute concentration
2) Sympathetic nervous system; activation causes constriction of blood vessels
What supplies the kidneys with blood and removal of blood? Describe the anatomy of the artery/ arteries.
A single renal artery and vein
-Artery branches into anterior/posterior divisions; gives rise to 5 segmental arteries
1) How do the kidneys manage surplus electrolytes?
2) How do they manage electrolyte deficiency?
1) Increasing elimination in urine
2) Decreasing urinary losses
1) When it comes to the kidneys, managing ____[excess/deficit]____is easier than managing ____[excess/deficit]____.
2) Give an example
1) excess is easier than deficit
2) Ex: water: Even if the person is not consuming water, kidneys must put out about 500mL urine each day to remove waste
What would happen if a person stopped consuming water? Why?
-Even if the person is not consuming water, kidneys must put out about 500mL urine each day to remove waste
-Water in urine comes from plasma
-A person without water will eventually urinate to death as plasma volume falls to fatal level
List the 9 main functions of the kidneys
Water balance
Solute concentrations
Electrolyte balance
Plasma volume
Acid base balance
Eliminating waste
Producing renin
Producing EPO
Activating Vit D
1) What 2 main things are included in the urinary system?
2) Where is urine first collected and channeled?
3) Each ureter carries urine from the _________ to the single __________
1) Organs that form urine (kidneys) and structures that carry urine for elimination
2) Collects in central cavity, the renal pelvis, and is then channeled into the ureter
3) kidney; bladder
1) What is the bladder?
2) Compare female and male urethras
1) A smooth muscle sac that contracts to empty urine via urethra
2) Female urethra is short and straight, male urethra is long
1) Male urethra also serves as passageway for __________.
2) ___________ enlargement can occlude the ___________, obstructing urine flow
3) What part of the kidney is made of striated triangles called renal pyramids?
1) semen
2) Prostatic; urethra
3) Renal medulla
1) What is the functional unit of the kidney? How many is in each kidney?
2) The arrangement of nephrons gives rise to two distinct regions; what are they?
1) Nephron; 1 million
2) Renal cortex and Renal medulla
What are the two main vascular components of a nephron?
Small afferent arterioles (from renal a.) and glomerulus (capillaries)
1) What supplies each nephron with blood? Where does the blood go?
2) What is a glomerulus? Where does fluid go once it leaves a glomerulus?
1) A small arteriole, delivers to glomerulus
2) Ball-like tuft of capillaries that filters blood; fluid then passes through tubular component
Besides the capillary bed, glomerular capillaries also form what? What does this do?
Efferent arteriole, unfiltered blood leaves through it
What is only place in the body where capillaries drain into arterioles rather than veins?
Glomeruli of the kidneys
1) What forms the tubular component of the nephron?
2) What does it encompass?
3) Is it divided?
1) Single layer of epithelial cells
2) Extends from glomerulus to renal pelvis
3) Divided into segments
1) Where does the tubular component of the nephron begin? Define this structure and what it does
2) Where does it go next?
3) Where next?
4) What does its last segment pass between?
1) Begins with Bowman’s capsule, the cup that surrounds glomerulus and collects fluid
2) Passes into proximal tubule, lies in cortex
3) Loop of Henle, dips into medulla then ascends
4) Afferent and efferent arterioles
1) What does the tubular component of the nephron do at the Loop of Henle?
2) What does it do as it ascends?
1) Dips into medulla then ascends
2) Passes between afferent and efferent arterioles
1) What are the vascular and tubular components of the nephron combined called?
2) What is this specialized region made of?
1) Juxtaglomerular apparatus
2) Vascular and tubular cells
1) The distal tubule of a nephron (after loop of henle/ ascending pt) empties into what? What can this structure receive fluid from?
2) Where does this structure go and empty into?
1) Collecting duct; fluid drained from up to 8 different nephrons
2) Descends through medulla to empty into renal pelvis
1) What are the two types of nephrons?
2) Where do all nephrons originate?
1) Cortical (80%) and juxtamedullary
2) The cortex
Describe the two main differences between the two types of nephrons
1) Cortical nephron: glomerulus lies in outer cortex
-Loop of Henle barely dips into medulla
2) Juxtamedullary nephron: glomerulus lies in inner cortex
-Loops of Henle dips deep into medulla
1) Peritubular capillaries of juxtamedullary nephrons form ________ that run with ________________.
2) What are these _______ called?
1) loops; loops of Henle
2) Vasa recta (“straight vessels”)
1) Collecting ducts run parallel to loops of Henle in what kind(s) of nephrons?
2) This parallel arrangement does what?
1) Juxtamedullary nephrons
2) Gives striated appearance to renal pyramids
What are the 3 basic processes of forming urine?
1) Glomerular filtration
2) Tubular reabsorption
3) Tubular secretion
1) What does blood enter during glomerular filtration?
2) Where does 20% percent of plasma that enters this structure go?
1) Blood enters glomerular capillaries
2) Filtered into the Bowman’s capsule
1) __________ of filtrate is formed collectively each minute, and _________ per day.
2) Average plasma volume is __________.
3) Kidneys filter entire plasma _____ times per day.
1) 125mL; 180L
2) 2.75L
3) 65x
1) What is tubular reabsorption? i.e. where is blood when this happens and where does it then go?
2) Where do those structures then take the blood?
1) As filtrate flows through tubules, it undergoes reabsorption into peritubular capillaries
2) Return it to venous system
True or false: Tubular reabsorption is a selective process
True
Of the 180L of filtered plasma, ________ is reabsorbed
178.5L
What is tubular secretion?
Selective transfer from peritubular capillary blood into the tubular lumen
What is the body’s second chance to eliminate waste?
Tubular secretion
How do the kidneys help with acid base balance?
Will conserve or excrete specific ions
1) What is renin important for?
2) What does it turn into? List the next 2 steps
1) Blood pressure
2) Renin > angiotensinogen > angiotensin I > angiotensin II
List the 3 parts of the tubular component of the nephron
1) Bowman’s capsule
2) Proximal tubule
3) Loop of Henle
What is urine excretion made of?
Filtrate that is not reabsorbed passes through renal pelvis is ultimately excreted as urine
Fluid filtered from glomerulus into Bowman’s capsule passes through what 3 three layers?
1) Glomerular capillary wall
2) Basement membrane
3) Inner layer of Bowman’s capsule
What do the layers fluid filtered from glomerulus pass through to get to the Bowman’s capsule do? (3 things)
1) Function as molecular sieve
2) Retains blood cells and plasma proteins
3) Passes H2O and smaller molecules
1) What forms the glomerular capillary wall?
2) Glomerular capillary walls have many pores that make them _______x more permeable to H2O and solutes than ___________________________.
1) Single layer of flattened epithelial cells
2) 100x; anywhere else in the body
1) What is the basement membrane?
2) Where is it?
1) Gelatinous layer of collagen and glycoproteins
2) Between glomerulus and Bowman’s capsule
1) What is an important property of glycoproteins for the basement membrane?
2) What are 99% excluded from filtrate? What happens to the 1% that slips through?
1) Negatively charged and repel even small proteins
2) Plasma proteins; 1% that slip through are degraded into amino acids in proximal tubule and reabsorbed, thus normal urine is protein free
The inner layer of Bowman’s capsule is made of what? Define this structure
Podocytes; footlike projections that cup the glomerular capillary
True or false: No local energy is used to move fluid across the membrane into Bowman’s capsule
True
How is fluid moved across the membrane into Bowman’s capsule?
1) Passive physical forces
2) Via fluid dynamic principles that we have already discussed (with 2 differences)
1) How permeable are glomerular capillaries? What is the significance of this?
2) Filtrate occurs where in the glomerular capillaries?
1) Much more permeable, so much more fluid is filtered at a given pressure
2) Across entire length of capillaries rather than near the beginning
What are the 3 forces of glomerular filtration? State whether each opposes or encourages filtration
1) Glomerular capillary blood pressure
-Favors filtration
2) Plasma-colloid osmotic pressure
-Opposes filtration
3) Bowman’s capsule hydrostatic pressure
-Opposes filtration
1) What does Glomerular capillary blood pressure depend on?
2) What is it? Is it higher or lower than other capillaries?
1) Heart contraction and resistance in afferent and efferent arterioles
2) 55mmHg, higher than other capillaries
1) What causes plasma-colloid osmotic pressure?
2) Can this thing be filtered? What does this do?
3) What does the concentration gradient do?
4) What is the average osmotic force?
1) Unequal distribution of plasma proteins across glomerular membrane
2) No, so they are in glomerular capillaries, but not in Bowman’s capsule
3) Establishes tendency of water to move from Bowman’s capsule into glomerulus (opposing filtration)
4) 30mmHg
1) What is Bowman’s capsule hydrostatic pressure? What is its amount?
2) What does it tend to do?
1) Pressure exerted by fluid in Bowman’s capsule, about 15mmHg
2) Push fluid out of capsule (opposing filtration)
What causes GFR?
Forces acting across glomerular membrane not being balanced
-3 forces acting across glomerular membrane not being balanced cause GFR to exist. Describe each of them (what each pressure is in mmHg and where it goes).
-What is net filtration?
1) 55mmHg glomerular capillary blood pressure into Bowman’s capsule
2) 30mmHg plasma-colloid osmotic pressure opposing filtration
3) 15mmHg Bowman’s capsule hydrostatic pressure opposing filtration
Net filtration = 10mmHg into Bowman’s capsule
1) What does GFR depend on? (3 things)
2) What is it a measure of?
1) Net filtration pressure, glomerular surface area, and permeability of glomerular membrane
2) How much blood passes through glomeruli each minute
What can affect GFR?
Changes in the opposing physical forces can affect GFR
Give 2 examples of how changes in the opposing physical forces can affect GFR
1) Decrease in plasma proteins (burns) can increase GFR, increase in plasma proteins (dehydration) will lower GFR
2) Urinary tract obstruction (kidney stone, enlarged prostate) can increase Bowman’s capsule hydrostatic pressure (decreases GFR)
Why can a decrease in plasma proteins (burns) increase GFR, and an increase in plasma proteins (dehydration) lower GFR?
Plasma protein concentration affects plasma-colloid osmotic pressure
Urinary tract obstruction (kidney stone, enlarged prostate) can increase what?
Bowman’s capsule hydrostatic pressure
How does the body regulate GFR?
By adjusting glomerular capillary blood pressure
1) Body regulates GFR by adjusting glomerular capillary blood pressure; what will increases and decreases in this type of BP do?
2) What two things largely determine glomerular capillary BP?
1) Increases will increase GFR, decreases will decrease GFR
2) MAP and afferent arteriole resistance
1) Two control mechanisms regulate GFR by collectively doing what?
2) What are the 2 mechanisms?
1) Regulating radius (resistance) of afferent arterioles
2) Autoregulation (intrinsic) and sympathetic control (extrinsic)
1) Describe autoregulation (intrinsic)
2) What does it resist? What does this prevent?
1) Kidneys maintain constant blood flow (and thus constant glomerular capillary blood pressure) despite changes in arterial pressure by altering afferent arteriole radius
2) Spontaneous changes in GFR; prevents momentary changes in BP from changing GFR
1) How does sympathetic control (extrinsic) of GFR relate to autoregulatory responses?
2) How is this achieved?
1) Override autoregulatory responses
2) By baroreceptor reflex response
1) What two baroreceptors are involved in the baroreceptor reflex response for extrinsic GFR control?
2) What does the brainstem do and why?
3) What does this response include?
1) Carotid sinus and aortic arch baroreceptors detect fall in BP
2) Initiates sympathetic stimulation of heart and vessels to increase cardiac output and peripheral resistance
3) Resistance of afferent arterioles, which are more sympathetically innervated than efferent arterioles)
1) In the baroreceptor reflex response of extrinsic GFR control, what happens to radius, resistance, blood flow, GFR, and fluid loss?
2) What happens to this reflex with increased BP?
1) Decreased radius, increased resistance, decreased blood flow, decreased GFR, decreased fluid loss to mitigate initial decrease in BP
2) Vasoconstrictor sympathetic activity is reduced, leading to opposite effects
1) The body reabsorbs valuable substances so that they are not lost through ________________ filtration.
2) Substances are returned from _____________ into __________________ capillaries.
1) glomerular
2) tubular lumen; peritubular
In each minute, how much is filtered and how much is reabsorbed?
125mL; 124ml
Tubular reabsorption is highly selective, what percents of water, sugar, and creatinine are absorbed?
-99% water and 100% sugar reabsorbed
-0% creatinine absorbed (waste product of muscle metabolism)
In transepithelial transport [of tubular reabsorption], a substance must do what 5 things?
1) Leave tubular fluid by crossing luminal membrane of tubular cell
2) Pass through cytosol to the other side of the tubular cell
3) Cross the basolateral membrane of the tubular cell into IF
4) Diffuse through IF
5) Penetrate capillary wall to enter plasma
During transepithelial transport (during tubular reabsorption), a substance must:
1) Leave tubular fluid by crossing __________________________ of the tubular cell
2) Pass through ___________ to the other side of the ________________
1) luminal membrane
2) cytosol; tubular cell
1) During transepithelial transport (during tubular reabsorption), a substance must cross what to reach the IF?
2) What must it do once it reaches the IF?
1) The basolateral membrane of the tubular cell into IF
2) Diffuse through IF
During transepithelial transport (during tubular reabsorption), a substance must do what to enter the plasma after it diffuses through the IF?
Penetrate capillary wall
Is tubular reabsorption passive or active? Explain and give examples
Involves passive and active steps depending on if local energy is used for a particular substance
-Active: glucose, amino acids, electrolytes
1) In tubular reabsorption, Na+ reabsorption depends on what? Where?
2) 80% of the energy spent by kidneys is used for what?
1) Na-K ATPase pump in basolateral membrane
2) Na+ transport
True or false: Different segments of the tubules transport differing amounts of Na+
True
1) Na-K pump transports Na+ out of _______________ into ______________ where it builds up
2) What does the Na-K pump use energy to do?
3) Where does the Na+ go?
1) tubular cell; lateral space
2) Move Na+ against concentration gradient
3) Diffuses down concentration gradient into interstitial fluid and then peritubular capillary
1) Total Na+ in body is reflected by what?
2) Na+ and Cl- account for ____% of _______ osmotic activity
1) Fluid volume
2) 90%; ECF
1) Na+ and Cl- account for 90% of ECF osmotic activity, so what happens when Na+ load is high?
2) What about when it’s low?
1) It “holds” water and fluid volume expands
2) Fluid volume reduces
1) Expansion of plasma volume __________ BP, reduction _____________ BP
2) Na+ regulating mechanisms therefore regulate what?
1) increases; decreases
2) Arterial blood pressure
Most important system for regulating Na+ is what?
Renin-angiotensin-aldosterone system (RAAS)
1) Renin (hormone) is secreted by what in response to what three things?
2) What sense these things? (2 things)
3) What reflex also stimulates renin secretion?
1) Juxtaglomerular apparatus; falling NaCl, fluid volume, and BP
2) Cells are sensitive to NaCl changes and kidneys also have intrarenal baroreceptors
3) Baroreceptor reflex sympathetic activity
1) What is natriuresis?
2) What two things inhibit Na+ reabsorption? What produces these?
3) When are these two things released?
1) Excretion of large amounts of sodium in urine.
2) ANP/BNP; heart.
3) When heart muscles detect stretch (which is due to expansion of circulating plasma volume).
Why do heart muscles detect stretch? What happens when they do?
Expansion of circulating plasma volume; heart releases ANP/BNP
What can BNP tell you?
How bad heart failure is
1) Nutritionally important molecules are completely reabsorbed by what mechanisms?
2) What is involved in this process?
1) Energy dependent mechanisms
2) Plasma membrane (carries them)
1) Plasma membrane carriers are specific to what?
2) Reabsorption limited by what? What happens when the limit is reached?
3) The concentration at which tubular maximum is reached is called what?
1) Plasma membrane carriers are specific to the substance being transported.
2) Number each of carrier in tubular cells, once they are saturated (“tubular maximum”) the substance will escape into urine.
3) Renal threshold.
Once transported into tubular cell, nutritionally important molecules do what?
passively diffuse down gradients into plasma
List the 3 things that are passively reabsorbed thanks to Na+ reabsorption and what happens with each
Na+ reabsorption facilitates passive Cl-, H2O, and urea reabsorption:
2) Cl-: reabsorbed down electrical gradient created by Na+
3) H2O: osmotically follows Na+
4) Urea: waste product from protein breakdown
limited permeability of which only allows 50% of urea to be reabsorbed
1) What does Na+ reabsorption facilitate?
2) Where is Cl- reabsorbed?
1) Passive Cl-, H2O, and urea reabsorption
2) Down electrical gradient created by Na+
1) What does O2 do during passive reabsorption?
2) What is urea? Is it all reabsorbed?
1) Osmotically follows Na+
2) Waste product from protein breakdown; limited permeability which only allows 50% of urea to be reabsorbed
What is the second chance to eliminate waste? What happens during it?
Tubular secretion; transepithelial transport in reverse direction compared to reabsorption
What are the most important ions involved in tubular secretion? Which is tightly controlled by the kidneys?
1) H+, K+, organic anions and cations
-Renal H+ secretion extremely important in acid-base balance. Increased acidity increases H+ secretion.
-K+ is tightly controlled by kidneys.
[Regarding tubular secretion] What is the significance of renal H+ secretion?
Extremely important in acid-base balance; Increased acidity increases H+ secretion.
What organic ions are secreted by the kidneys? [tubular secretion]
Why?
1) Hormones like prostaglandin and epinephrine; need to be removed after they have served their purpose to avoid prolonged activity
2) Many foreign compounds are organic ions including food additives, drugs, environmental pollutants.
1) Of the ______filtered per day, ______ is excreted as urine
2) What does urine contain?
1) 180L; 1.5L
2) waste products and (spillover of excess quantities of substances that should have been absorbed)
At normal fluid balance, are body fluids hypotonic, hypertonic, or isotonic?
Isotonic
1) Define hypotonic
2) Define hypertonic
1) Too diluted; too much H2O relative to solutes.
2) Too concentrated; not enough H2O.
1) The kidneys have what kind of gradient? What does this allow?
2) How?
1) A vertical osmotic gradient, enables them to vary the concentration of the urine
2) Allows kidneys to eliminate excess H2O if body fluids hypotonic or preserve H2O if fluids are hypertonic
What allows the kidneys to eliminate excess H2O if body fluids are hypotonic or preserve H2O if fluids are hypertonic?
Vertical osmotic gradient
1) The vasa recta follow the same deep loops of Henle in what kind of nephrons?
2) Is flow in these nephrons forward or opposite? What is this related to?
1) Juxtamedullary nephrons
2) Opposite (countercurrent); vertical osmotic gradient
1) What establishes the vertical osmotic gradient? What preserve it?
2) What does this allow for?
1) The loops establish; vasa recta preserve
2) Water to be reabsorbed (urine concentrated)
Describe the permeability of the descending and ascending limbs of the loop of Henle
1) Descending: Permeable to H2O but not Na+
2) Ascending: Permeable to Na+ but not H2O
A positive feedback loop is created by the vertical osmotic gradient and continues “countercurrent multiplication” until when? Where?
Maximum concentration of 1200mOsm/L is reached at the bottom of the loop
1) What is vasopressin also called?
2) What creates it? What stores it? When is it secreted?
3) What two things are only permeable to H2O in the presence of vasopressin?
1) ADH
2) Created by hypothalamus, stored in posterior pituitary gland, secreted when ECF is too concentrated (H2O deficit)
3) Distal and collecting tubules
1) What condition in the body does the hypothalamus detect?
2) What secretes vasopressin?
2) What does vasopressin do? Where?
4) What gets reabsorbed to counter the condition the hypothalamus detects?
1) Hypertonicity
2) Posterior pituitary
3) Permits H2O permeability in distal/collecting tubules
4) H2O counters hypertonicity
1) Define micturition
2) Ureters carry urine to the bladder; what is the bladder lined with?
3) What is the important property of this lining?
1) Process of bladder emptying (urinating)
2) Smooth muscle which can stretch tremendously
3) Richly supplied with parasympathetic fibers which cause contraction which empties urine via urethra
Exit of urine is guarded by what two things?
What is one reinforced by? Which is the last part of the bladder?
1) Internal urethral sphincter; last part of bladder
2) External urethral sphincter; reinforced by pelvic diaphragm
What supplies the external urethral sphincter and pelvic diaphragm with innervation? When do they fire?
Motor neurons; continuously firing until they are inhibited
Micturition involves what two mechanisms?
1) Micturition reflex (spinal reflex)
2) Voluntary control
1) What activates the micturition reflex?
2) What during this reflex inhibits motor-neurons and what else does it cause?
1) Stretch receptors
2) Parasympathetic action; bladder contraction
1) Define voluntary control of micturition
2) What two things are tightened because of this?
3) Is there a limit on this?
1) A learned control mechanism of voluntary overriding of reflex inhibition
2) External sphincter and pelvic diaphragm
3) Yes, there is a limit to this before reflex inhibitory input becomes too strong
Renal failure has wide ranging consequences; list 8 of them
1) Uremic toxicity: retention of waste products causing a wide variety of toxic effects including platelet dysfunction, nerve damage, GI symptoms
2) Metabolic acidosis: inability to secrete H+
3) Potassium retention: increases cardiac and neural excitability
4) Sodium imbalance: blood pressure, edema (excess) or hypotension, shock (deficiency)
5) Electrolyte imbalances
6) Loss of plasma proteins
7) Anemia: decreased EPO
8) Immune depression: overwhelmed by accumulated waste
1) Define uremic toxicity and what it causes. Then give 3 examples of what it causes.
2) Define metabolic acidosis
1) Retention of waste products, causes a wide variety of toxic effects.
-platelet dysfunction, nerve damage, GI symptoms
2) Inability to secrete H+
What is the narrow range of ECF pH?
7.35-7.45
True or false: The cells of complex organisms are only able to survive within a narrow range of ECF composition
True
What pHs of ECF would you die at?
Below 6.9 or above 8.0
What is the “internal pool” of a substance?
the amount of that substance in the ECF
True or false: Input (from ingestion or metabolic production) must balance output (excretion or consumption)
True
1) What is the Balance Concept important in?
2) What is it?
1) Homeostasis.
2) Input (from ingestion or metabolic production) must balance output (excretion or consumption).
1) Define stable balance
2) Define positive balance
3) Define negative balance
1) Input equals output
2) Input exceeds output
3) Output exceeds input
1) What is the most abundant component in the body?
2) In a discussion of fluid balance, it is acceptable and common to use what two terms interchangeably?
1) Water
2) Fluid and water
1) What two substances is water distributed between in the body?
2) Describe this distribution
1) ICF and ECF
2) ICF composes 2/3rds of body water, ECF 1/3rd
1) ECF’s portion of water is further divided into what two categories?
2) What else is included? Why aren’t they a big deal?
1) Plasma and IF
2) Lymph and transcellular fluids (CSF, synovial fluid, pleural fluid, etc.).
-Minor considerations in fluid balance bc they’re an insignificant fraction of body H2O
1) ECF components (plasma and IF) are separated by what?
2) Plasma and IF are nearly identical in composition except for what thing?
1) Walls of blood vessels
2) IF lacks plasma proteins
H2O is freely and passively exchanged via what to maintain fluid balance?
Capillary walls
1) Transfer of H2O between plasma and IF is governed by what?
2) What is this called?
1) Imbalances across the capillary walls
2) Pressure or concentration gradients
1) ECF and ICF are separated by __________________
2) Define this structure
1) plasma membranes
2) Highly selective membranes with active and passive mechanisms
1) Transfer of H2O between ECF and ICF governed by ___________________
2) Describe the hydrostatic pressure of both ECF and ICF
1) concentration gradients
2) Both low and fairly constant
1) All exchanges of __________ between ________ and external world must occur through ECF
2) What is the fluid that is acted upon to control fluid volume and composition?
1) H2O; ICF
2) Plasma
1) What happens if plasma’s volume or composition is changed? Why?
2) What does this imply about control mechanisms acting on plasma?
1) The volume and composition of the IF is also changed; because of the free exchange of plasma across capillary walls
2) They indirectly regulate the IF (and therefore essentially regulate the entire ECF volume)
What are the two factors in regulating fluid balance in the body? Why is each regulated and what controls each?
1) ECF volume: Regulated to maintain blood pressure.
-Controlled by salt balance.
2) ECF osmolarity: Regulated to prevent swelling or shrinking of cells.
-Controlled by water balance
1) What is regulated to maintain BP? What controls it?
2) In other words, _______________________ = (_________________________)= BP reduction
1) ECF volume; controlled by salt balance.
2) ECF reduction = (plasma volume reduction) = BP reduction
1) What are the short term controls of ECF output (and thus BP)?
2) What are the long term controls?
1) Baroreceptor reflex, automatic fluid shifts between plasma and IF due to hydrostatic pressures
2) Kidneys regulate output, thirst regulates input
1) What primarily control ECF volume?
2) Is salt synthesized? Explain
1) Salt balance (increased Na+ reabsorption, passive Cl- reabsorption, increased H2O reabsorption)
2)Not synthesized; ingested and typically in quantities significantly higher than body’s need for replacing salt losses
1) What two things are by far the most abundant solutes in the ECF?
2) What two things are responsible for ICF osmolarity?
1) Na+ and Cl-
2) K+ and anionic proteins
1) Any change of H2O (that is not accompanied by a comparable change in solutes) will lead to a change in what?
2) Vasopressin regulates permeability of what to what?
1) ECF osmolarity
2) Renal tubule to H2O
1) Loss of ECF H2O will lead to _____________ ECF
2) Excess ECF H2O will lead to ______________ECF
1) Hypertonic ECF
2) Hypotonic ECF
1) Body must then regulate ECF osmolarity within narrow limits to prevent cells from doing what?
2) How does it do this?
1) Shrinking or swelling
2) By controlling water balance through fluid shifts
1) Describe the fluid shifts that help regulate ECF
osmolarity
2) What does vasopressin do for ECF osmolarity?
1) Water moving from area of low solute concentration to high solute concentration until osmolarity between the areas equilibrates
2) Regulates permeability of renal tubule to H2O
1) Define thirst
2) Where is the thirst center? What is this near?
1) Subjective sensation that drives an individual to ingest fluids
2) In hypothalamus near vasopressin-secreting cells
List 4 factors that affect fluid balance [which is the result of ECF volume and ECF osmolarity]
1) Thirst
2) Hypothalamic osmoreceptors
3) Left atrial volume receptors
4) Angiotensin II
1) What do hypothalamic osmoreceptors detect?
2) Increased ECF osmolarity (too little H2O) does what to thirst? What does that do?
1) Changes in ECF osmolarity
2) Increases thirst; increases vasopressin
1) Left atrial volume receptors respond to what?
2) What can this suppress/ stimulate?
1) Stretch caused by blood (reflects ECF volume)
2) Vasopressin and thirst
What two things does Angiotensin II stimulate?
Thirst and vasopressin
Sodium balance:
1) Kidneys conserve Na+ and limit excretion to what?
2) What increases Na+ excretion?
1) A small percentage of the initial sodium-filtered load
2) Elevated renal capillary hydrostatic pressure
Sodium balance:
1) Extracellular Na+ is regulated by what two things?
2) What do diuretics promote?
1) Renin-angiotensin-aldosterone system and atrial natriuretic peptide
2) Na+ excretion by the kidney
Potassium balance:
1) What is the potassium balance sensitive to? (4 things)
2) What is the major cause of K imbalance? What does this parallel changes in?
1) Blood chemistry, hormones, drugs, and pathological conditions
2) Abnormal renal K+ excretion
-Dietary K intake
Potassium balance:
1) True or false: Sodium deprivation does not lead to K+ loss by the kidneys
2) What does increased plasma potassium concentration do?
1) True
2) Increases aldosterone secretion and plasma aldosterone
Calcium regulation:
1) 99% of calcium is stored where? Where is the remaining stored?
2) What does Ca mainly come from?
1) In bones.
-Remaining in cells
2) Dairy products in the diet
1) Most of the __________ filtered through the glomeruli is reabsorbed in the proximal convoluted tubule
2) Control of the excretion of the above substance occurs in what two places?
1) Ca2+ filtered through the glomeruli is reabsorbed in the proximal convoluted tubule
2) Loop of Henle and distal nephron
Calcium regulation:
1) Calcium reabsorption is increased by what medications?
2) What hormone increases reabsorption?
1) Thiazide diuretics
2) Parathyroid hormone (PTH)
1) What percent of magnesium is in the bones? What percent is in the cells? What percent is in the ECF?
2) What is the the major site for the reabsorption of filtered Mg2+?
3) What percent is reabsorbed in the PCT?
1) 60% present in bone, 39% in cells, 1% in the ECF
2) The loop of Henle
3) 25% in the proximal convoluted tubule
1) What does low plasma Mg2+ cause?
2) What does high plasma Mg2+ cause?
1) Neuromuscular hyperirritability and cardiac arrhythmias
2) A sedative effect; may cause cardiac arrest.
Phosphate regulation:
1) Where is most phosphate stored? How much exactly?
2) What is the major site of its reabsorption?
1) 85% in the bone.
2) Proximal tubule
Phosphate regulation:
1) What is the significance of phosphate in the urine?
2) What inhibits phosphate reabsorption?
1) An important pH buffer
2) PTH
1) Chronic renal disease often leads to what?
2) What are the two reasons?
1) An elevated plasma phosphate
2) Decreased GFR and calcium lowers
