Set 7 (Part II) Flashcards
What is the countercurrent of exchange mechanism important for?
To create a salty medulla
What does the countercurrent of exchange mechanism refer to?
The flow of the vasa recta is opposite to the flow of the fluid moving down the tubule
What kind of urine does ADH create?
Salty, small volume of concentrated urine
How does an increase in water uptake due to thirst affect blood pressure?
- Increases blood pressure
- Cardiovascular reflexes lower the blood pressure rapidly
Describe the mechanism of aldosterone.
1) Aldosterone combines with a cytoplasmic receptor
2) Initiates transcription in the nucleus
3) New protein channels are made + increase in Na+/K+ channels
4) Na+/K+ ATPase speeds up
5) Increased Na+ absorption and K+ secretion
What is the net result of aldosterone?
- Increased Na+ reabsorption
- Increased K+ secretion into the lumen of the distal tubule
Where does aldosterone act?
Principal cells in the distal tubule
What kind of receptor does aldosterone bind?
Cytoplasmic receptor
What must be monitored if the aldosterone system is modified by drugs?
Potassium
What happens when the body needs salt?
Aldosterone is secreted
What happens when there is low blood pressure?
Renin-angiotensin-aldosterone system (RAAS)
What constantly produces angiotensinogen?
The liver
What occurs in granular cells of the kidney when blood pressure decreases?
- Granular cells produce renin
- Renin activates angiotensinogen
What activates ANG I in plasma?
Blood vessel endothelial contains ACE (enzyme), which converts ANG I to ANG II in plasma
What is the function of ANG II on arterioles?
- Vasoconstriction
- Increases blood pressure
What is the function of ANG II on the cardiovascular control center in the medulla oblongata?
- Increase in cardiovascular response (increases depolarization to contract the heart more forcefully)
- Increases blood pressure
What is the function of ANG II on the cardiovascular control center in the hypothalamus?
- Increases vasopressin
- Increases thirst
- Increases volume and maintains osmolarity
What is the function of ANG II on the cardiovascular control center in the adrenal cortex?
- Releases aldosterone
- Increases Na+ reabsorption
- Increases volume and maintains osmolarity
How does aldosterone increase water retention?
Increase in Na+ reabsorption (and Cl- passive reabsorption) increases water-holding capacity
What happens when there is high blood pressure?
Atrial Natriuretic Peptide (ANP) increases water loss
What is ANP secreted by? In response to what?
- Atria of the heart
- In response to being stretched by Na+ retention, expansion of ECF volume, and increase in arterial pressure
How does ANP affect the distal tubule?
- Inhibits Na+ reabsorption
- Increases Na+ output in urine
- Increases water loss
How does ANP affect afferent arterioles?
- Afferent arteriole vasodilation
- Increase in GFR
How does ANP affect the kidneys?
Inhibits renin secretion
What would be a secondary disease to chronic high blood pressure?
- Kidney disease
- Increase in GFR puts a huge strain on the kidneys
How does ANP affect the sympathetic nervous system?
- Decrease in cardiac output and total peripheral resistance
- Decrease in arterial blood pressure
What are causes of renal failure?
- Infectious organisms
- Toxic agents
- Inappropriate immune responses
- Obstruction of urine flow
- Insufficient renal blood supply
How is Buerger’s disease related to the kidney?
Immune system attacks epithelial cells in the kidney, which leads to kidney failure
What hormones do the kidneys release?
- Erythropoietin
- Renin
What do the kidneys convert into its active form?
Vitamin D
Ion regulation is a key feature of kidney function. What happens to the resting membrane potential of a neuron if extracellular K+ levels decrease?
Hyperpolarizes (becomes more negative)
What happens to the force of cardiac contraction if plasma Ca2+ levels decrease substantially?
Force of contraction decreases
Describe the movement of blood in the renal portal system.
- Renal arteriole
- Glomerulus
- Efferent arteriole
- Peritubular capillaries
- Renal vein
If the net filtration out of glomerular capillaries occurs, then you know that capillary hydrostatic pressure must be (greater than/less than/equal to) capillary colloid osmotic pressure.
greater than
If net reabsorption into peritubular capillaries occurs, then capillary hydrostatic pressure must be (greater than/less than/equal to) the capillary colloid osmotic pressure.
less than
What is filtration?
The movement of fluid from blood into the lumen of the nephron
Where does filtration ONLY take place?
Renal corpuscule, where the walls of glomerular capillaries and Bowman’s capsule are modified to allow bulk flow of fluid
What is reabsorption?
Process of moving substances in the filtrate from the lumen of the tubule back into the blood flowing through peritubular capillaries
What is secretion?
Selectively removes molecules from the blood and adds them to the filtrate in the tubule lumen
Which process is more selective: secretion or glomerular filtration? Why?
Secretion is more selective that usually uses membrane proteins to move molecules
Which portion of the nephron is responsible for the isomotic reabsorption of solutes and water?
Proximal tubule
Which portion of the nephron is the primary site for creating dilute urine?
Loop of Henle
Amount excreted = amount filtered ___ amount reabsorbed ___ amount secreted
Amount excreted = amount filtered - amount reabsorbed + amount secreted
Name one way in which filtration and secretion are alike.
They both represent movement from ECF into the lumen
A water molecule enters the renal corpuscule from the blood and ends up in the urine. Name all the anatomical structures that the molecule passes through on its trip to the outside world.
- Glomerulus
- Bowman’s capsule
- Proximal tubule
- Loop of Henle
- Distal tubule
- Collecting duct
- Renal pelvis
- Ureter
- Bladder
- Urethra
Do molecules sent for filtration pass through the Bowman’s capsule or glomerulus first?
Glomerulus THEN Bowman’s capsule
What would happen to the body if filtration continued at a normal rate but reabsorption dropped to half the normal rate?
The body would run out of plasma in under an hour
What glomerular cells alter blood flow through capillaries?
Mesangial cells by contraction
What is the consequence of increased resistance of efferent arterioles?
- Decreases renal blood flow
- Increases hydrostatic pressure
- Increases glomerular filtration rate
What is the consequence of vasoconstriction of the afferent arteriole?
- Increases resistance
- Decreases renal blood flow
- Decreases capillary blood pressure (hydrostatic pressure)
- Decreases glomerular filtration rate
What are the two factors that determine glomerular filtration rate?
- Net filtration pressure (determined by renal blood flow and blood pressure)
- Filtration coefficient (determined by the surface area of the glomerular capillaries and the permeability of interface between the capillary and Bowman’s capsule)
What occurs to GFR if resistances increases in the afferent arteriole?
Decrease in GFR
What occurs to GFR if resistances increases in the efferent arteriole?
Increase in GFR
Why is the osmotic pressure of plasma in efferent arterioles higher than that in afferent arterioles?
Osmotic pressure is higher in efferent arterioles due to the same amount of protein in a smaller volume
Define the myogenic response.
The intrinsic ability of vascular smooth muscle to respond to pressure changes
What is tubuloglomerular feedback?
- Paracrine signaling mechanism
- Changes in fluid flow through the loop of Henle influence the GFR
What occurs in terms of the myogenic response when smooth muscle in the arteriole wall stretches because of increased blood pressure?
- Stretch-sensitive ion channels open and the muscle cells depolarize
- Depolarization opens voltage-gated Ca2+ channels and the muscle contracts
- Vasoconstriction increases resistance to flow
- Decrease in blood flow decreases filtration pressure in the glomerulus
How does a decrease in GFR influence blood volume?
Helps the body conserve blood volume
How is neural control of GFR mediated?
Sympathetic neurons that innervate both the afferent and efferent neurons
What occurs to GFR if systemic blood pressure drops sharply?
Sympathetically induced vasoconstriction of the arterioles decrease GFR and renal blood flow
If systemic blood pressure remains constant but the afferent arteriole of a nephron constricts, what happens to renal blood flow and GFR in that nephron?
Renal blood flow and GFR decrease
A person with cirrhosis of the liver has lower-than-normal levels of plasma proteins and consequently a higher-than-normal GFR. Explain why a decrease in plasma protein concentration causes an increase in GFR.
With fewer plasma proteins, the plasma has lower-than-normal colloid osmotic pressure opposing GFR, so GFR increases
What is the primary driving force for most renal reabsorption?
The active reabsorption of Na+
What kind of transport does urea reabsorption utilize? Where?
- Passive reabsorption in the collecting duct
- Only if there is a urea concentration gradient
Why does the net pressure gradient favour reabsorption in peritubular capillaries?
Because the hydrostatic pressure that exists along the entire length of the peritubular capillaries is less than the colloid osmotic pressure
What kind of transport is secretion?
Active because it requires moving substances against their concentration gradients
Give an example of net reabsorption and net secretion.
- Net reabsorption: urea clearance
- Net secretion: penicillin clearance
Differentiate the internal and external sphincter.
- Internal sphincter: continuation of the bladder composed of smooth muscle
- External sphincter: skeletal muscle controlled by somatic motor neurons
At any given time, what percentage of cardiac output goes to the kidneys?
20-25%
Name the three filtration barriers that solutes must cross as they move from plasma to the lumen of Bowmen’s capsule. What components of blood are usually excluded by these layers?
- Glomerular capillary endothelial
- Basal lamina
- Epithelium of Bowman’s capsule
- Blood cells and plasma proteins are excluded
What force promotes glomerular filtration? What forces oppose it?
- Capillary hydrostatic pressure promotes filtration
- Fluid pressure in Bowman’s capsule and colloid osmotic (oncotic) pressure of plasma oppose it
In which segment of the nephron does most reabsorption take place?
Proximal tubule
If a solution is filtered and not reabsorbed from the tubule, where does it go?
Excreted in urine
What solute that is normally present in the body is used to estimate GFR in humans?
Creatine
What is micturition?
Urination
Which of the following is UNLIKELY to be a consequence of kidney disease?
A) electrolyte imbalance
B) hyperglycemia
C) edema
D) anemia
B) hyperglycemia
The ability of the nephron to filter substances based on size and charge is NOT due to the __________.
A) epithelium of Bowman’s capsule
B) capillary endothelium
C) hydrostatic pressure
D) basal lamina
C) hydrostatic pressure
Glucose reabsorption from the renal filtrate is due to __________.
A) active transport along the descending loop of Henle
B) osmotic pressure in the glomerular capillaries
C) sequential active transport and facilitated diffusion by the cells of the proximal tubule
D) osmosis and simple diffusion along the distal tubule
C) sequential active transport and facilitated diffusion by the cells of the proximal tubule
If clearance of a substance is greater than GFR, the substance is __________.
A) net secreted by the kidney
B) net reabsorbed by the kidney
C) glucose
D) both secreted and reabsorbed
A) net secreted by the kidney
What are two systems that compensate for acid-base disturbances?
A) respiratory and cardiovascular
B) renal and respiratory
C) cardiovascular and renal
D) renal and digestive
B) renal and respiratory
In a dehydrated person, the kidneys compensate for changes in extracellular fluid volume and osmolarity by __________.
A) increasing the amount of water that is reabsorbed from the collecting duct
B) increasing the rate of glomerular filtration
C) reducing vasopressin release
D) increasing the amount of water excreted
A) increasing the amount of water that is reabsorbed from the collecting duct
Which hormone acts as a form of reflex (systemic) control to increase the glomerular filtration rate?
A) angiotensin II
B) atrial natriuretic peptide
C) renin
D) aldosterone
B) atrial natriuretic peptide
Which is NOT true of thirst?
A) Thirst is a physiological mechanism for maintenance of fluid and electrolyte balance.
B) High osmolarity stimulates thirst.
C) Angiotensin II stimulates thirst.
D) Thirst (and drinking) can increase plasma volume.
A) Thirst is a physiological mechanism for maintenance of fluid and electrolyte balance.
High ECF K+ stimulates __________.
A) increased secretion of vasopressin and reduced sodium reabsorption
B) increased secretion of atrial natriuretic peptide
C) decreased secretion of renin
D) increased synthesis and secretion of aldosterone
D) increased synthesis and secretion of aldosterone
The primary function of the vasa recta is to __________.
A) maintain the medullary concentration gradient
B) promote sodium and water excretion in the nephron
C) establish the medullary concentration gradient
D) fine-tune water reabsorption in order to maintain body volume
A) maintain the medullary concentration gradient
Angiotensin II alters kidney function by __________.
A) decreasing the glomerular filtration rate and increasing sodium reabsorption along the distal tubules
B) increasing water reabsorption along the proximal tubule and increasing potassium reabsorption along the distal tubules
C) reducing thirst and reducing the water permeability of the collecting duct
D) decreasing sodium reabsorption along the descending loop of Henle and increasing the water permeability of the ascending loop of Henle
A) decreasing the glomerular filtration rate and increasing sodium reabsorption along the distal tubules
The effects of angiotensin II on the central nervous system are to __________.
A) increase thirst and increase the cardiac output and peripheral vasoconstriction
B) increase activity of the respiratory control center
C) inhibit secretion of vasopressin from the posterior pituitary gland
D) act on the medulla oblongata to decrease blood pressure
A) increase thirst and increase the cardiac output and peripheral vasoconstriction
An ACE (angiotensin-converting enzyme) inhibitor would be used to treat __________.
A) hypertension, since ACE inhibition will result in decreased secretion of vasopressin
B) hypertension, since ACE inhibition will decrease the rate of urine production
C) hypotension, since ACE inhibition will result in increased secretion of vasopressin
D) hypotension, since ACE inhibition will decrease the glomerular filtration rate
A) hypertension, since ACE inhibition will result in decreased secretion of vasopressin
Which of the following is appropriately linked to increased renin secretion?
A) increased secretion of atrial natriuretic peptide
B) increased formation of angiotensinogen
C) increased secretion of erythropoietin
D) increased sodium reabsorption in the distal nephron
D) increased sodium reabsorption in the distal nephron
Suppose that your company is developing a new drug that blocks aldosterone synthesis. You would expect that patients given this drug in clinical tests would respond with __________.
A) an immediate increase in blood pressure
B) hypernatremia (high plasma sodium) and hypokalemia (low plasma potassium)
C) a higher concentration of potassium in their urine than in patients given a placebo
D) a higher concentration of sodium in their urine than in patients given a placebo
D) a higher concentration of sodium in their urine than in patients given a placebo
In which of the following locations is the osmolarity of the filtrate the greatest?
A) the base of the loop of Henle
B) near the top of the ascending limb of the loop of Henle
C) at the end of the proximal tubule
D) near the top of the descending limb of the loop of Henle
A) the base of the loop of Henle
A vasopressin receptor antagonist would __________.
A) cause aquaporins to be inserted into the apical membranes of collecting duct cells
B) increase aldosterone secretion
C) prevent membrane recycling in collecting duct cells
D) cause vasoconstriction and increased blood pressure
C) prevent membrane recycling in collecting duct cells
Which part of the nephron always has low permeability to water, regardless of hormone levels?
A) descending loop of Henle
B) ascending loop of Henle
C) collecting duct
D) proximal tubule
B) ascending loop of Henle
