1 - Renal 02 Flashcards
Urea is essential in allowing the kidney to:
develop concentrated urine
this is why people with high protein diets can concentrate urine better
The _______ serve as countercurrent exchangers, minimizing the washout of solutes from the medullary interstitium.
vasa recta
An increase in medullary blood flow would have what effect on urine concentration?
Decreased ability to concentrate urine d/t decreased solute load
Why does a decrease in ADH lead to a less concentrated renal medulla?
Less urea is being reabsorbed in the medulla
Why is tubular fluid in the thick ascending loop so dilute?
the loop is completely impermeable to water
BUT
all of the sodium, chloride etc is sucked out, leaving dilute tubular fluid
In the late distal tubule and cortical collecting tubules, the osmolarity of the tubular fluid depends on:
the amount of ADH
How can you tell if DI is nephrogenic or central?
Give desmopressin
If it gets better, it has to be caused by decreased ADH (central)
If it doesn’t get better, the problem is that the kidneys can’t respond to ADH
Plasma osmolarity can be roughly calculated by:
multiplying serum sodium by 2.1
A more exact calculation for plasma osmolarity would be:
POSM = 2.1 [PNa + PGluc + PUrea]
How does increased plasma sodium concentration stimulate ADH secretion?
Causes osmoreceptor cells in the hypothalamus to shrink
Shrinkage of these cells causes them to fire
Action potentials are conducted to the posterior pituitary
ADH is released
What effect does nausea have on ADH levels?
Increases ADH levels for up to an hour after vomiting
Name six stimulants of ADH
- Increased osmolarity
- decreased blood volume
- decreased blood pressure
- nausea
- hypoxia
- Morphine and Nicotine
Name three drugs that decrease ADH stimulation
clonidine
haldol
alcohol
Name five things that increase thirst
increased plasma osmolarity
decreased BP
decreased blood volume
increased angiotensin II
dry mouth
What effect do aldosterone and angiotensin have on sodium plasma concentration?
None! They control the total body sodium. Not sodium concentration.
Name four factors that cause potassium to shift into cells
Insulin
Aldosterone
B-adrenergic stimulation
alkalosis
Name 7 factors that cause potassium to shift out of cells
insulin deficiency (diabetes)
Aldosterone deficiency (addison disease)
B-adrenergic blockade
Acidosis
Cell Lysis
Exercise
Increased plasma osmolarity
Most of the daily potassium reabsorption and excretion occurs where?
the late distal and cortical collecting tubules
Which cells in the late distal and cortical collecting tubules secrete potassium?
Principal cells
In patients with Addison’s disease, serum potassium levels are:
extremely high
In a high-sodium diet, aldosterone would be low, so you’d think potassium would be high. But it isn’t. Why?
the low aldosterone decreases the amount of K secreted, but the high tubular flow rate that results from being fluid overloaded increases potassium excretion, so the balance stays pretty much the same
Acute acidosis ______ potassium secretion
reduces
How is most calcium excreted?
feces
Hypocalcemia causes ________ excitability
Hypercalcemia causes _______ excitability
increased
decreased
Why are patients with alkalosis more susceptible to hypocalcemic tetany?
hydrogen ion concentration alters calcium binding. When there’s a high hydrogen ion concentration, more calcium is free (ionized). When there’s a low hydrogen ion concentration, less calcium is free (ionized), which means less calcium is technically available for use
Name six factors that decrease calcium excretion
Increased PTH
decreased BP
decreased blood volume
Increased plasma [phos]
Alkalosis
Vit D
Name five factors that increase Ca excretion
Decreased PTH
increased blood volume
increased BP
decreased plasma [phos]
acidosis
Name four factors that increase Phos excretion
increased dietary intake
PTH
metabolic acidosis
HTN
Name four factors that decrease Phos excretion
decreased intake
Vit D
Alkalosis
Thyroid Hormone
Magnesium concentration is directly related to _______ concentration
calcium
as calcium excretion increases, magnesium excretion increases (and vice versa)
What is pressure natriuresis?
As blood pressure increases, sodium excretion increases
what is pressure diuresis?
An increase in BP increases diuresis
Why do so many patients in heart failure need ACE inhibitors?
under normal circumstances, angtiotensin II causes a large amount of water and sodium to be reabsorbed
BUT with a normal heart, this results in almost no change in ECF volume BECAUSE the increased volume causes increased pressure diuresis.
BUT in a sick heart, it can’t pump effectively enough to increase pressure in the kidney and cause pressure diuresis. So angiotensin II is still retaining Na, but the kidney isn’t compensating via pressure diuresis.
Water accumulates and causes CHF
Which does ADH effect more: ECF volume or plasma [Na]?
Plasma sodium concentration
ADH actually causes very little ECF overload, even when present in large amounts BECAUSE of pressure natriuresis
BUT excess ADH creates ECF that is extremely low in sodium, because sodium is not being reabsorbed with the water
AND sodium excretion is increased by pressure natriuresis
destruction of ______ causes an inability to create ADH
supraoptic nuclei
Why does blood volume increase as a woman becomes more pregnant?
As vascular capacitance increases (due to the constant formation of new blood vessels), the kidneys retain salt and water to add volume to essentially fill a bigger tank
Why are the kidneys more resilient to ischemia than other organs?
As perfusion decreases, so does the GFR, which means the kidney is expending WAAAYY less energy reabsorbing sodium
What causes acute glomerulonephritis?
abnormal immune reaction that damages the glomeruli
occurs 1-3 weeks after infection d/t antibody production
What kind of pathogen is usually the instigator of glomerulonephritis?
Group A Beta Strep
What is tubular necrosis?
destruction of the epithelial cells of the tubules
What causes Acute Tubular Necrosis?
Either severe ischemia or toxins/meds
In CKD, serious symptoms aren’t seen until the number of functional nephrons decreases to ______
20-25% of normal
What is the most common cause of ESRD?
Diabetes
Why does lupus often lead to kidney failure?
Causes chronic glomerulonephritis
minimal-change nephropathy is:
protein loss with no visible defect in the basement membrane
most common in children aged 2-6
What is isosthenuria?
inability of the kidney to concentrate urine
What is renal tubular acidosis?
Inability of the tubules to secrete H results in a severe loss of bicarb
What is Fanconi Syndrome?
increased urinary excretion of virtually all amino acids, glucose, and phosphate
What is Bartter Syndrome?
Decreased Sodium, Chloride, and Potassium Reabsorption in the Loops of Henle
Impaired NCCK
What is Liddle Syndrome?
Increased sodium reabsorption
autosomal-dominant disorder resulting from various mutations in the amiloride-sensitive epithelial sodium channel (ENaC) in the distal and collecting tubules
Renal glucose release is stimulated by _____ and inhibited by ______
epinephrine
insulin
_______ suppresses glucose release in both the kidneys and liver
insulin
All glomeruli are located in the _______
cortex
The structural unit of the kidney is the ______
the functional unit of the kidney is the _______
lobe
nephron
How many lobes are there in each kidney?
14
Each lobe is composed of:
a medullary pyramid and the overlying cortex
______ cells create a matrix and support the glomerular capillaries
mesangial
Podocytes are responsible for forming:
filtration slits that modulate filtration
The endothelium, basement membrane, and podocytes are covered with ______ to prevent proteinuria
anionic protein molecules
juxtaglomerular cells are located in the ______ and release ________ in response to ______
Afferent arteriole
renin
sodium changes in the macula densa
the wall of the ______ is the only surface in the nephron that contains microvilli
proximal convoluted tubule
Compare the ascending and descending thin loops of henle
Descending: no active transport, highly permeable to water
Ascending: permeable to ions, impermeable to water
The distal tubule extends from the ______ to the _____
macula densa
collecting duct
Principal cells and intercalated cells make up the epithelium of the:
distal tubule
Principal cells reabsorb _____ and secrete ______
sodium and water
potassium
The ________ is the only blood supply to the medulla
vasa recta
closely follows the loop of henle
What is the function of the uroepithelium?
lines the entire urinary tract
maintains barrier between water and solutes in the urine and the blood supply
What is the trigone?
smooth triangular area lying between the openings of the two ureters and the urethra
the internal urethral sphincter is made of:
the external is made of:
smooth muscle
striated muscle (under voluntary control)
Which nerves innervate the external urethral sphincter?
somatic motor neurons in the pudendal nerves
Where does blood that is not filtered through the glomerulus go?
Through the efferent arteriole into the peritubular capillaries
What effect does parasympathetic stimulation have on renal perfusion?
There’s almost no parasympathetic innervation to the kidneys
What is the role of prostaglandins in regulation?
dampen vasoconstriction caused by sympathetic nerves and angtiotensin II
Prevent harmful vasoconstriction and renal ischemia
Low serum plasam levels will ______ the GFR
decreases the effective oncotic pressure that would normally keep fluid in the glomerular capillaries instead of flowing into the capsule (being filtered)
increases GFR
High serum plasma levels will ______ the GFR
decrease
Keeps fluid in the glomerular capillaries instead of being filtered into the glomerulus
How are chloride, water, and urea absorbed?
passively
but linked to the active transport of sodium
What is the primary function of the proximal tubule?
active sodium reabsorption
everything else is cotransported with sodium and water is reabsorbed by osmosis with sodium concentration
How does the structure of the loop of henle alter the efficiency of water conservation?
The longer the loop, the greater the ability to concentrate urine
