What artery carries blood to the kidneys?
Renal Artery
What 2 structures make up the renal corpuscle?
Glomerulus & Bowman’s Capsule
What structure brings blood to the renal corpuscle?
Afferent arteriole
What’s not filtered out in the formation of urine?
Red blood cells
Plasma proteins
How does the body regulate pressure to the renal corpuscle?
Smooth muscle of afferent and efferent arterioles
What is RPF?
Renal Plasma Flow; vol of blood plasma delivered to the kidneys per unit time
What is FF?
Filtration Fraction; proportion of fluid reaching the kidneys which passes into the renal tubules
What is the typical filtration fraction? Renal plasma flow?
FF= 20% RPF= 550 ml/min
RPFxFF=what?
GFR; glomerular filtration rate
Contracting the efferent arteriole would alter which factor: RPF or FF?
FF, would increase glomerular pressure
What are the 2 methods of altering RPF?
Increase cardiac output, dilate afferent arteriole
T/F: Fenestrae are small pores and slit pores are larger pores.
False: Fenestrae=large, slit pores=small
T/F: Excretion rates are less than filtration rates for most electrolytes like sodium, chloride, and bicarbonate.
True
T/F: Amino acids and glucose are completely reabsorbed from the tubules under normal conditions.
True
When excretion rate=filtration rate + secretion rate, what does this mean?
Solute is being excreted in large amounts in the urine, ex: drugs, organic acids & bases
What is the capillary filtration coefficient? (Kf)
Measure of permeability and surface area of the glomerular capillary
Normally functioning adults should have a ___ glomerular hydrostatic pressure, and a ___ filtration coefficient.
High glom HP, Large filtration coefficient
What is unique about the layers of the glomerular capillary membrane?
3 layers instead of normal 2; (endothelium, basement membrane, and epithelial layer of podocytes)
T/F: The positive charge of plasma proteins prevents it from exiting the glomerular capillary.
False: plasma proteins are negatively charged
The filtration barrier of glomerular capillary membrane is highly dependent on molecule __ and ____ ____.
molecule size and electrical charge
Albumin becomes filtered and is appearing in the urine, what is the likely cause?
Basement membrane lost it’s negative electrical charge and proteins were allowed to be filtered
Kf x Net filtration pressure equals what?
Kf (capillary filtration coefficient) x Net Filtration Pressure= Glomerular Filtration Rate (GFR)
What are the 4 determining pressures of GFR?
- Hydrostatic Pressure of Glomerular Capillaries
- HP of Bowman’s Capsule
- Colloid Osmotic Pressure of Glom. Capillaries
- COP of proteins in Bowman’s Capsule
What pressure should be 0 if the body’s working properly?
Bowman’s Capsule Osmotic Pressure
T/F: Osmotic pressure can also be called oncotic pressure.
True
Name 2 things that would decrease Kf thus decrease GFR?
- Decr amt of functioning glomerular capillaries
2. Incr thickness of capillaries
What happens to the GFR if you were to increase the pressure in the Bowman’s capsule?
Decr. GFR
T/F: If you incr. the glomerular colloid osmotic pressure, it would decr. the GFR.
True
When glomerular hydrostatic pressure is __, it promotes filtration and thus increases GFR.
Increased
T/F: If you dilate the afferent arteriole, glomerular capillary hydrostatic pressure increases.
True
What two things happen when you constrict the efferent arteriole?
Glomerular capillary hydrostatic pressure increases,
Glomerular Filtration Rate increases.
T/F: Manipulating the efferent arteriole is just as efficient as manipulating the afferent arteriole when it comes to changing GFR.
False: Manipulating AFFERENT much more effective, than manipulating efferent.
Where are the 3 places renal vascular resistance occurs?
Interlobular arteries
Afferent arterioles
Efferent arterioles
T/F: The renal cortex receives most of the blood flow into the kidney whereas the renal medulla only receives about 1-2%.
True
Sympathetic NS stimulation (and its hormones like epinephrine and norepinephrine) would have what effect of GFR?
Decreases GFR; try to hold onto our fluid
Endothelin is a vasoconstrictor released in response to injury, what would it do to GFR?
Decrease GFR
What 3 vasodilators would increase renal blood flow and increase GFR?
- Prostaglandins
- Bradykinin
- Endothelial-derived nitric oxide
What is the myogenic mechanism & what is it’s purpose?
Ability of individual blood vessels to resist stretching during increased arterial pressure;
Protects kidneys from damage during incr. BP
Glomerular Filtration - Tubular Reabsorption + Tubular Secretion = what?
Urine formation
What is the most vital aspect of determining excretion rate?
Tubular reabsorption
T/F: Tubular reabsorption is highly selective and glomerular filtration is non-selective.
True
T/F: Tubular reabsorption is both an active and passive process.
True
What is ultrafiltration?
Water and solutes moving in bulk flow thru the peritubular capillary wall into the blood
What are the 2 types of active transport?
Primary-coupled w/ hydrolysis of ATP
Secondary-coupled indirectly to the energy source
Na-K ATPase pump is an example of which active transport: primary or secondary?
Primary
T/F: Water is always absorbed via the passive mechanism called osmosis.
True
Sodium Glucose co-transporters (SGLT1 & SGLT2) are located where?
SGLT2-early part of proximal tubule (90% of glucose reabsorption)
SGLT1-later part of proximal tubule (remaining 10%)
What is a transport maximum?
The limit to the rate at which a solute can be transported during active reabsorption or secretion.
T/F: Sodium and glucose do not have transport maximums.
False: Sodium does NOT.
Glucose does!
T/F: Sodium transport in the proximal tubules obey gradient time transport principles.
True (meaning higher concentration of Na, more reabsorption or slower flow rate–>more Na reabsorbed.)
T/F: Almost all creatinine filtered at the glomerulus is excreted.
True
Where is the majority of water and sodium reabsorbed: Proximal tubule, Descending limb, Ascending limb, or Distal tubule?
Proximal Tubule (65% reabsorbed)
What 4 things are rapidly reabsorbed in the first half of the proximal tubule?
Sodium, glucose, amino acids, water
What sort of things are secreted into the tubules?
Organic acids & bases, drugs, toxins
What are the 3 parts of the Loop of Henle?
- Thin descending limb
- Thin ascending segment
- Thick ascending segment
20% of water is reabsorbed in what part of the Loop of Henle?
Thin descending limb
What is occurring in the thick ascending segment of the Loop of Henle?
Active reabsorption of Na, Cl, & K
The Na-H counter-transport mechanism is found where and what does it do?
Thick ascending segment; sodium reabsorbed and hydrogen secreted.
Which part of the Loop of Henle is impermeable to water?
Thick ascending segment, (concentrates the urine as needed)
How is the distal tubule divided?
First portion=macula densa
Next part=diluting segment
What two things is the diluting segment of the distal tubule impermeable to?
Water & Urea
Calcium, bicarbonate and magnesium are absorbed in the __ ___ limb in the Loop of Henle.
Thick Ascending
What 2 cells are found in the late distal tubule and cortical collecting duct?
Principal cells & Intercalated cells
Principal cells are responsible for __ reabsorption and __ secretion.
Na reabsorption, K secretion
What is the responsibility of intercalated cells?
H secretion, bicarbonate and K reabsorption
What hormone controls the reabsorption of Na and the secretion of K?
Aldosterone
Regarding the late distal tubule and cortical collecting duct, high ADH leads to a __ permeability to water.
high
What 2 substances may be reabsorbed in the medullary collecting duct that is responsible for urine concentration?
Water, Urea
Without ADH, we would excrete ___ quantities of ___ urine.
…large quantities of dilute urine.
Where is aldosterone secreted from?
Zona glomerulosa cells of the adrenal cortex
Incr extracellular K concentration–> __ angiotensin II levels, which leads to aldosterone being released.
Incr.
What is the function of ADH/vasopressin?
Conserve water by increasing water permeability in distal tubule and collecting duct
T/F: ANP inhibits reabsorption of water and sodium, increasing urinary excretion and lowering blood volume (thus lowering BP).
True
What effect does PTH have on tubular reabsorption?
Increases Ca reabsorption (Loop of Henle, Distal tubule)
Inhibit phosphate reabsorption (proximal tubule)
Increases Mg reabsorption (Loop of Henle)
Is angiotensin II present when there is high or low BP?
Low, increases Na and water reabsorption
Angiotensin II has what effect on efferent arterioles?
Constricts
The rate of what hormone secretion determines whether the kidneys excrete dilute or concentrated urine?
ADH
T/F: Osmolarity is held constant throughout the proximal tubule.
True
Which segment of the Loop of Henle is not permeable to water?
Thick ascending limb
Where does the change in osmolarity occur?
Leaving the Loop of Henle (goes from 300 mOsm/L to 200 mOsm/L)
What test is used to assess the concentration of urine?
Urine Specific Gravity Test
What does a high specific gravity indicate?
High concentration of urine
T/F: The range for a specific gravity test is about 1.002-1.028 g/ml.
True
What are the 2 basic requirements for forming a concentrated urine?
- High level of ADH
2. High osmolarity of the renal medullary interstitial fluid
What is the countercurrent mechanism useful for?
Creating a hyperosmotic renal medullary interstitial fluid
Osmoreceptor cells in the ___ ___ shrink causing it to fire and stimulate the __ pituitary to release ADH.
anterior hypothalamus, posterior
ADH affects which 3 areas to become more permeable to water?
Late distal tubule
Cortical collecting tubules
Medullary collecting ducts
What is the anteroventral region of the 3rd ventricle also referred to as?
AV3V region
What are cells in the AV3V region stimulated by?
Stimulated by a small increase in extracellular fluid osmolarity
A decrease in arterial pressure causes a(n) ___ in ADH.
increase
T/F: Nausea, hypoxia, and drugs all decrease ADH secretion.
False: …increase ADH secretion
Is alcohol an inhibitor of ADH secretion?
Yep
Decreased blood volume and decreased BP has what effect on thirst?
Increases thirst
T/F: Gastric distention decreases thirst.
True
What is the obligatory urine volume loss?
The amount of urine that needs to be excreted in order to rid the body of waste products.
