Exam III Flashcards
What are the three components of the filtration barrier?
Endothelium
Basement membrane
Podocytes
What is the glomerular filtration rate determined by?
osmotic and hydrostatic forces.
capillary filtration coefficient
What is the daily glomerular filtration rate
125 mL/min or 180 L/day
What are some diseases that lower the glomerular filtration coefficient?
diabetes, hypertension
What is minimal change nephropathy?
A loss of negative charge in the basement membrane
What is hydronephrosis?
Distension and dilation of renal pelvices
How is glomerular filtration rate calculated?
GFR = K1(Pg-Pb-Lg+Lb)
Pg = glomerular hydrostatic pressure Pb = Bowman's capsule hydrostatic pressure Lg = glomerular capilly coilloid osmotic pressure Lb = colloid osmotic pressure of Bowman's capsule
Increasing what factor will increase glomerular colloid osmotic pressure?
filtration fraction
What effect does arterial pressure have on GFR?
it increases it.
What effect does afferent pressure have on GFR?
It decreases it
What effect does efferent pressure have on GFR?
It increases it
What effect does activation of the sympathetic system have on GFR?
It constricts arterioles and decreases blood flow and GFR.
What hormones affect GFR?
Norepinephrine
Endothelin
Angiotensin II
Endothelial-derived NO
Prostaglandins and bradykinin
What is endothelin released by?
damaged vascular endothelial cells of the kidneys and other tisues.
What effect does endothelin have on GFR?
it leads to vasoconstriction and reduced GFR.
How does angiotensin affect GFR?
It constricts Efferent arterioles, which increases GFR.
Afferent arterioles are protected against the effects of angiotensin II.
What is the origin of nitric oxide?
endothelial cells.
What is the effect of nitric oxide on GFR?
It helps maintain renal vasodilation
What is the effect of prostaglandins and bradykinins on GFR?
It offsets effects of sympatheti and angiotensin II vasoconstrctor effects.
What does autoregulation refer to?
maintaining a relatively consant GFR and renal blood flow.
What are the two tubuloglomerular feedback mechanisms for autoregulation?
afferent
efferent
What are the comonents of the juxtraglomerular complex (autoregulation)?
macula densa cells
juxtaglomerular cells in afferent and efferent arterioles.
When GFR decreases, how is the flow rate affected?
The flow rate int he loop of Henle slows down. There is increased reabsorption of sodium and chloride ions here, and less at the macula densa.
Once the macula densa reabsorbs less sodium chloride, what does it signal?
increased renin release from the JG cells. This increases angiotensin and efferent arteriolar resistance.
Where is glucose absorbed?
proximal convoluted tubule
What receptor reabsorbs 90% of glucose in the early proximal tubule?
SGLT2 via secondary active transport
What is the difference between sodium absorption in the first and second half of the proximal tubule?
In the first half, reabsorption is via co transort along with glucose, amino acids, and other solutes.
In the second half, reabsorption is mostly with chloride ions.
How is sodium transported in the peoximule tubule?
via antiport with H+
What is the thin descending segment of the loop of henel highly permeable to?
water.
It is also moderately permeable to most solutes, including urea and sodium.
What is the thin ascending segment of the loop of Henle impermeable to?
water
What diuretics are used at the thick ascending segment of the loop of Henle?
furosemide
etacrynic acid
bumetanide
What is the distal tubule impreameble to?
water and urea
Where are principal and intercalated cells found?
In the late distal tubule and collecting tubules
What do principal cells reabsorb and secrete?
reabsorb Na+, secrete K+
What diuretics are used at the principal cells?
spironolactone, eplerenone, amilrodie, triameterene
What do intercalated cells reabsorb and secrete?
reabsorb potassium, secrete hydrogen ions.
It also reabsorbs water in the presence of ADH
What is the permeability to water in the medullary collecting duct controlled by?
ADH
what does the collecting duct reabsorb and secrete?
reabsorb: Na, Cl, H2O (in the presence of ADH), urea, HCO3
secrete: H+
What is the source of aldosterone?
adrenal cortex
What is the functon of aldosterone?
increase sodium reabsorption and stimulate potassium secretion.
Where is the site of actionof aldosterone?
the principal cells of cortical collecting ducts
An increase of what ionin the extracellular fluid causes the secretion of aldosterone?
potassium
What happens in Addison’s disease?
A marked loss of sodium and accumulation of potassium due to the absence aldosterone.
What syndrome involves the hypersecretion of aldosterone?
Conn’s syndrome
What does angiotensin II directly stimulate?
sodium reabsorption in proximal tubules, loops of Henle, distal tubules and collecting tubules.
What is he source of ADH?
posterior pituitary
What is the function of ADH?
to increase water reabsorption
Where does ADH bind?
to V2 receptors in late distal tubules, collecting tubules and collecting ducts.
It increases the formation of cAMP
What is the source of ANP?
cardiac atrial cells in response to distension
what is the function of ANP?
to inhibit reabsorption of sodium and water.
What is the source of PTH?
parathyroid glands
What is the function of PTH?
increases calcium reabsorption
How much water can be excreted by the kidneyes per day when there is a large excess of water in the body?
20 L/day
What is the maximal urine concentration that the kidneys can produce?
1200 - 1400 mOsm/L
What are the requirements for forming concentrated urine?
presence of ADH
High osmolarity of the renal medullary interstitial tubule.
What is the obligatory urine volume, and why is it necessary?
0.5 L/day; it is excreted in order to get rid of waste products of metaolism and ions that are ingested.
Where in the kindey tubule are most of the filtered electrolyetes reabsorbed?
in the proximal tubule.
What is the descending loop of Henle permeable to?
water
When does the tubular fluid become more dilute?
as it moves up the thin ascending loop of Henle. Sodium chloride is reabsorbed here.
What is the role of the osmoreceptor ADH feedback mechanism?
It controls extracellular fluid sodium concentration and osmolarity.
When the extracellular fluid osmolarity is high, what effect does this have on osmorecetor ells in the anterior hypothalamus?
The cells shrink. ADH is then released, which increases water permeability in distal nephron segments.
When does extracellular osmolarity increase?
When therei s a deficit in water. This causese ADH secretion and subsequent water reabsorption.
What is the extracellular fluid potassium concentration?
4.2 mEq/L
What is the relationship between insulin and potassium?
Insulin stimulates potassium uptake by cells.
What is the relationship of aldosterone and potassium?
Aldosterone increases potassium uptake by cells.
what is the disorder that involves an excess secretion of aldosterone?
Conn’s syndrome
What is the disorder that invovles a deficiency in aldosterone secretion?
Addison’s disease
What is the relationship between beta-adrenergic stimulation and potassium?
epinephrine stimulates potassium uptake by cells.
What is the relationship between metabolic acidosis and extracellular potassium?
extracellular potassium increases in metabolic acidosis due to reuctionin activity of the Na/K ATPase pump.
What are the effects of hyperkalemia?
cell lysis
strenous exercise
increased extracellular fluid osmolarity
What is a buffer?
A substance that can reversibly bind H+.
What are three important buffer systems?
bicarbonate
phosphate
proteins as buffers
What is the most important extracellular buffer system?
bicarbonate buffer system
What is metabolic acidosis?
a decreased concentration of bicarbonate
What is metabolic alkalosis?
an increased concentration of bicarbonate
What is respiratory acidosis?
an increased concentration of carbon dioxide
What is respiratory alkalosis?
a decreased concentration of carbon dioxide.
What role does the phosphate buffer system play?
It biffers renal tubular fluid and intracellular fluids
What is the primary method for removing nonvoltaile acids?
by excretion.
In order to reabsorb bicarbonate, what must happen to it?
It must react with secreted hydrogen ion to form carbonic acid before it can be reabsorbed.
What are the three ways that extracellular H+ is regulated?
Reabsorption of filtered bicarbonate ions
Secretion of hydrogen ions
Production of new bicarbonate ions.
Where in the kidney tubules does hydrogen ion secretion and reabsorption occur?
Hydrogen ion secretion occurs via secondary active transport in all parts of the tuules except the descending and ascending limbs of the loops of Henle.
Where does primary acive hydrogen secretion begin?
In thelate distal tubules (intercalated cells)
Where does the majority of bicarbonate reabsorption occur?
proximal tubule
How are acidosis and alkalosis corrected?
via incomplete titration. Each time a hydrogen ion is formed in the tubular epithelial cells, a bicarbonate ion is formed and released back into the blood.
How does the tubular epithelium secrete hydrogen?
via primary active transport
How does the proximal tubule secrete hydrogen?
via secondary counter-transport.
What is the lower limit of pH that can be achieved in normal kidneys?
4.5
The loss of bicarbonate ions is the ___ as adding hydogen ions to the extracellular fluid.
same
Why can only a small partof the excess hydrogion secrete be excreted in the ionic form in urine?
Because the minimal urine pH is about 4.5.
How are excess hydrogen ions eliminated?
Through binding with phosphate or ammonia ions.
How can the kidneys correct alkalosis?
by failing to reabsorb all the filtered bicaronate ion
When does acidosis occur?
when the ratioof bicarbonate ion to carbon dioxide in extracellular fluid decreases.
What is the primary compensatory resonse of respiratory acidosis?
Increase in plsam bicarbonate ion
What is the primary compensatory response for metabolic acidosis?
increase ventilation rate
When does alkalosis occur?
When there is an increase in the ratio of bicarbonate to hydrogen ion concentration.
What is the primary compensatory response of alkalosis?
reduction in plasma bicarbonate ion concentration caused by renal excretion of bicarbonate ion.
what is the primary compensatory response of metabolic alkalosis?
decreased ventilation\
Increased renal bicarbonate ion excretion.
What is total lung capacity?
the maximum volume of gas the lungs can hold.
What is tidal volume?
the volume of air that is inspired or expired with each breath at rest. 500 ml
What is insiratory reserve volume?
Volume f air that can be inspired in addition to tidal volume with forceful inspiration. 3000 mL
What is expiratory reserve volume?
Additional volumeof air that can be expired at end of tidal volume by forceful expiration. 1100 mL
What is residual volume?
volume of air remaining in lungs after force expiration. 1200 mL.
What vital capacity?
The sum of all the volumes that can be insired or exhaled. 4600 mL
What is total lung capacity?
The sum of all the volumes = vital capacity plus residual volume. 5800 mL.
What is inspiratory capacity?
The sum of all volumes above resting capcity = tidal volume plus inspiratory reserve volume. 3500 mL
What is functional residual capcity?
2300 mL. The sum of volumes below resting capacity = expiratory reserve volume + residual volume.
What is minute ventilation?
Total volume of gases moved into or out of the lungs per minute; calculated as breaths per minute x tidal volume.
What is alveolar ventilation?
Total volume of gases that enter spaces participating in gas exchange per minute. Calculated as breaths per minute x (tidal volume - dead space).
What is anatomic dead space?
trachea, bronchi and bronchioles
What is physiological dead space
anatonmic dead space + ventilated alveoli with poor or absent perfusion.
What is the total dead psace in a normal individual?
0.15 L.
How is alveolar ventilation calculated?
0.35 x breathing rate.
What is pleural presure?
pressure of the fluid between parietal pleura and the visceral pleura.
What is alveolar pressure?
Pressure of the air inside the alveoli
What is transpulmonary pressure?
Difference between the alveolar pressure and the pleural pressure.
What is compliance?
The extent to which lungs will expand for each unit increase in the transpulmonary pressure. it is a measure of the expansibility of the lungs and trachea.
How is compliance calculated?
increase in volume/increase in pressure
What is surfactant produced by?
type II alveolar ells.
Why does a saline-filled lung expand more easily than an air-filled lung?
beacuse there is an absence of surface tension forces. Therei s no air-fluid interface.
What happens if air passages laeading from the alveoli are blocked?
the surface tension in he alveoli collapses the alveoli.
What would happen if there were no surfactant?
Pressure would be about 4.5 times as great in the lungs.
What is the high pressure, low flow irculation?
thoracic aorta to bronchial arteries
What is the low pressure, high flow circulation?
pulonary artery and branches to alveoli.
There is high compliance.
What is pulmonary arterial pressure?
24/9 mm H
What is mean pulmonary arterial pressure?
15 mm Hg
What is let atrium pressure?
8 mm Hg
What is the pressure gradient in the pulmonary system?
7 mm Hg
How does failure of the left side of the heart affect pressure?
pressure builds up in pulmonary circulation. Blood volume and pressure are increased.
What is a physiologic shunt?
it contains blood that has bypassed the pulmonary capillaries.
What occurs when oxygen concentration in the alveoli is 70% or more below normal?
adjacent vessels constrict. Those alveoli that are poorly ventilated get even less blood while those with adequate ventilation get more blood.
What is the flow in zone 1?
no blood flow
What is the flow in zone 2
intermittent blood flow only during systole
What is the flow in zone 3?
continuous blood flow
What flow is found in the apices?
zone 2 flow. Exercise can convert apices from zone 2 to zone 3 flow.
What is the result of obstructing blood supply to one normal lung?
blood flow through the other lung is doubled. The pulmonary pressure in the other lungs is only slightly increased.
What are agents that constrict pulmonary arterioles?
norepinephrine
epinephrine
angiotensin II
some prostaglandins
What are some agenst that dilate pulmonary arterioles?
isoproterenol
acetylcholine
What is the result of sympathetic vasoconstriction in the pulmonary system/
pulmonary blood flow is decreased by 30%, and blood is mobilized from pulmonary reserves.
Pulmonary arterial pressure rises little during maximum exercise. Why is this so?
becaue capillaries open and flow rate increases.
In left heart failure, what occurs at the left atrium?
blood begins to dam up.
What is the mean filtration pressure in the lungs?
1 mm Hg
What is the most common cause of pulmonary edema?
left sided heart failure or mitral valve disease.
Damage of pulmonary blood capillary membranes can also occur.
What happens if the pressure in the lungs becomes positive (greater than -4 mm Hg)?
the lungs tend to collapse.
What are causes of pleural effusion?
blockage of lymphatic drainage from pleural cavity
Cardiac failure
Reduced plasma colloid osmotic presure
Infection/inflammation
How does hypoxia affect presure in the pulmonary artery?
pressure is increased due to prostaglandins.
What are the results of a bronchial obstruction?
Decline in pH and vasoconstriction of pulmonary vessels.
What is the most abundant gas in air?
nitrogen
What is daltons law?
Ptotal = sum of partial pressures
What is Boyle’s law?
P = 1/V
What is Henry’s law?
the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
What is pressure directly proportional to?
the concentration of the gas molecules.
How is partial pressure calciulated?
partial pressure = [dissolved gas]/sol. coefficient
What is the relationship between vapor pressure and temperature?
as vapor pressure increases, temperature increases.
What factors affect the rate of gas diffusion in a fluid?
solubility of gas in the fluid
Cross sectional area of the fluid
Distance through which the gas must diffuse
Molecular weight of the gase
Temperature of the fluid
What is oxygen concentration in the alveoli controlled by?
rate of absorption of oxygen into the blood
rate of new oxygen entry into the lungs
Carbon dioxide concentration is controlled by what factors?
rate of carbon dioxide excretion
alveolar ventilation
What factors determine how rapidly a gas will pass through the respiratory membrane?
membrane thickness
surface area
diffusion coefficient of gas
partial pressure difference of gas between two sides of the membrane.
What does the Va/Q ratio refer to?
alveolar ventilation/blood flow
When Va/Q = 0, what type of obstruction i spresent?
an airway o bstruction. There is no ventilation, but there is perfusion. The blood gas composition remains unchanged.
When Va/Q = infinity, what type of obstruction is present?
a vessel obstruction. There is ventilation, but no gas exchange.
A physiologic shunt is made.
What is physiologic dead space?
shunted blood + anatomic dead space
When diffusing capacity increases during exercise, what happens in the lungs?
There is a more ideal V/Q ratio
There is increased surface area of capillaries participating in diffusion.
What factors determine tissue PO2?
Rate of oxygen transport to the tissues
Rate of oxygen consumption by the tissues
When PO2 is ___, oxygen binds with hemoglobin
high
When PO2 is ___, oxygen is released from hemoglobin.
low
What factors cause the oxygen-hemoglobin curve to shift to the right?
increased hydrogen ions
increased CO2
Increased temperature
increased BPG
What direction is the oxygen-hemoglobin curve shifted when there is an increase in carbon dioxide and H+ ions?
to the right
What direction is the oxygen-hemoglobin curve shifted when there is a decrease in blood carbon dixode and H+ ions?
to the left
How is carbon dioxide transported?
A small amount is dissolved in the blood
70% is transported as carbonic acid
Remainder is transported as carbamino hemoglobin
What is the bohr effect?
An increase in blood carbon dioxide causese oxygen to be displaced from hemoglobin. This shifts the oxygen-hemoglobin curve to the right.
What is the Haldane effect?
Binding of oxygen with hemoglobin displaces carbon dioxide from blood. The binding of oxygen cauese hemoglobin to become a stronger acid, and more acidic hemoglobin ha less of a tendency to bind with carbon dioxide.
What two respiratiory groups are located in the medullary respiratory centers?
dorsal respiratory group
ventral respiratory group
What respiratory groups are located in the pontine respiratory centers?
apneustic center
pneumotaxic center
What is the functionof the dorsal respiratory group?
It sets the basic rhythm of respiration.
What respiratory group establishes the ramp signal?
dorsal respiratory group
How is respiration controlled?
by limiting the point at which ramp suddenly ceasese. The earlier ramp ceases, the shorter the duration of inspiration and respiration.
What does a strong PRG signal result in?
30 - 40 breaths/minute
A weak PRG signal results in 3-5 breaths/minute.
What does the pneumotaxic center conrol?
the rate and depth of breathing.
The loss of function of what respiratory center causese prolonged inspiratory gasping?
apneustic center
What respiratory group is inactive during normal quiet respiration?
ventral respiratory group
What complex generates the timing and length of the respiratory rhythm?
the pre-botzinger complex
What is the Hering-breuer inflation reflex?
Stretch receptors in muscular portions of walls of bronchi and bronchioles activate dorsal respiratory group neurons. This inhibits the inspiratory ramp signal.
What is the relationship between chemoreceptors and hypoxia/hypercapnia?
chemoreceptors increase their rate of activity when hypoxia or hypercapnia occur.
Where are central chemoreceptors located?
on the ventral surfae of the medulla. They are indirectly sensitive to carbon dioxide levels int he blood.
Where are peripheral receptors located?
in the aortic arch. They are sensitive to concentrations of oxygen, carbon dioxide and hydrogen ions.
What are central receptors sensitive to?
H+.
Sensitivty to increased levels of carbon dioxide lasts for several hurs, but then begins to decline. This is due to adjustments by what organ?
The kidneys.
They increase bicarbonate levels in the blood.
Where are most peripheral receptors located?
in the carotid bodies at the bifurcation of the common carotids.
What are the two types of carotid body cells?
type I (glomus) and type II (sustenacular cells)
What effect does decreased PO2 have on channels?
It closes channels and results in a depolarization that opens calcium channels, leading to neurotransmitter release.
Where are slow-adapting stretch receptors located?
within the airways of the lungs.
What do signals from the slow adapting stretch receptors do?
terminate inspiration
prolong expiration
What are signals for the slow adapting stretch receptors important for?
controlling respiration in infants and adults during exercise.
What is the function of rapidly-adapting pulmonary stretch receptors?
eliciting a cough.
Where are J receptors located?
in the alveolar wall.
What are J receptors sensitive to?
pulmonary edema
What does the stimulation of J receptors elicit?
a cough and tachypnea
What is Cheyne stokesbreathing
hyperpnea
gradual decrease
apnea
repeat of pattern
What factors can cuase Cheyne-Stokes breathing?
A long delay in the transport of bood from the lungs to the brain.
Increased negative feedback.
