Flashcards in Renal: Tubular Reabsorption and Secretion Deck (61):
What is the most prevalent cation in the body?
What is the most prevalent anion in the body?
Creates concentration gradient as moves through medulla and has some reabsorption
Loop of Henle
Use a membrane protein to facilitate diffusion of ion from high to low concentration
Primary Active Transport
Rely on Na+ gradient by Na+ ATPase active transporter
Secondary Active Transport
What's the majority of ions in Extracellular Fluid?
What's the majority of ions in Intracellular Fluid?
True/False: Sodium always moves UP its concentration gradient
What transporter is on the Apical membrane?
Na+ - Glucose via Secondary Active Transport by Symport. Glucose moves UP its concentration gradient.
What transporters are on the Basolateral membrane?
Na+ - Potassium. Secondary Active Transport by Antiport ; GLUT-2. Sodium and Glucose goes into the blood. Potassium pumped back into blood and tubular lumen
Under normal conditions, Glucose is HIGHLY reabsorbed and freely filtered. What happens with Glucose in Diabetics?
High Blood Glucose level. Glucose is in the urine. Glucose is filtered but not reabsorbed, thus it is excreted.
Transporters' Maximum (Tmax) differs between Nephrons. Which have higher and lower Tmax?
Longer Prox. Tubule - More Transporters, Higher Tmax
Shorter Prox Tubule - less Transporters, Lower Tmax
What happens if Glucose levels are "below, at, and above" Tmax?
Below Tmax: No Glucose in urine
At Tmax: No Glucose in urine
Above Tmax: Glucose in urine
What helps with reabsorption in the Proximal and Distal Tubule?
Microvilli to increase surface area for reabsorption
What are the characteristics of Organic Substances (about 100% are all reabsorbed in Proximal Tubule)?
Reabsorbed similar way to Na+/Glucose
Have Secondary Active Transport
Use Transporters..exhibit Tmax
Has Specificity (D vs. L Glucose
Krebs cycle intermediates
above what is normally filtered
inhibitable by drugs and disease
NOT outside the proximal tubule
GFR X Px
Filtered Load (FL)
Ex: 180 L/day X 140 mEq/L=25,200 mEq
True/False: Sodium is reabsorbed in all parts of the Renal Nephron/Tubule
Chloride is an example of Para-cellular Pathway because?
Chloride (neg. charge) is pulled across tight junctions because of Na+ and other organic solutes' movement/reabsorption
Not reabsorbed across membrane
While sodium is reabsorbed along Apical membrane what follows it for re-absorption too?
Water. Every time sodium and organic ions are reabsorbed, water follows
Descending limb of Loop of Henle is permeable and impermeable to what?
permeable to water
impermeable to solutes
Ascending limb of Loop of Henle is permeable and impermeable to what?
permeable to solutes
impermeable to water
What are the cell types in the Distal Tubule?
Principal Cells - in latter DT (Aldosterone-mediated)
Intercalated Cells (alpha and beta) - in medullary collecting duct
Aldosterone (steroid) causes:
Increase Na+/K+ ATPases on Basolateral membrane
Open Na+ channels on Apical membrane
Open K+ channels on Apical membranr
Mechanisms at the Early part of Distal Tubule
Block Na+/Cl- transporter. Cause No re-absorption of water and sodium...increase urine
Mechanisms at the late part of Distal Tubule and Collecting Duct
Block Na+ channels on Apical membrane
Block Aldosterone function
Cause no re-absorption of water and sodium...increase urine
Concentration of Solutes
Potassium (consumed from diet) is stored where?
Stored inside cells
What is the net affect of Normal-High K diet on Distal Tubule and Cortical Collecting Duct?
What is the net affect of Low K diet on Distal Tubule and Cortical Collecting Duct?
Potassium, cation, is reabsorbed by "Bulk Flow" although a lot is not reabsorbed, it is not reabsorbed across membrane, but is not electrical charge dependent. What pathway and ion is similar?
Similar to being pulled like Chloride but isn't electrical charge dependent
Majority of Potassium is excreted where?
Least Potassium is excreted where?
Control of Potassium has what kind of feedback?
Aldosterone is impacted by what?
Blood Pressure Levels (thus, blood volume levels)
High Potassium levels cause Aldosterone to be _____?
Low Potassium levels cause Aldosterone to be _____?
What is blood volume (blood pressure) relationship to potassium?
Low BV, Low K+
High BV, High K+
Sequence of events to restore Low Blood Volume levels to normal:
Aldosterone release causes Increased Na+/H20 reabsorption which Increases BV, BP, and Potassium secretion levels
Relationship between plasma K+ levels and Aldosterone
Increased plasma K+ concentration, Increased Aldosterone Secretion
Decreased plasma K+ concentration, Increased Aldosterone reabsorption
Calcium is important for ______
Muscle contractility and 2nd messenger system
Vitamin D is essential for absorption of what?
Calcium is highly reabsorbed
Less than 5% of Calcium is in Urine
Calcium and Phosphate are always connected. They bind to one another in bones (shouldn't bind together in blood). Is Calcium active when bound to Phosphate?
What is Parathyroid Hormone (PTH) impacts on Calcium and Phosphate?
Increases calcium, Decreases Phosphate
Phosphate is more excreted than Calcium
3-20% of Phosphate is in Urine
When there's High Blood Calcium levels, Thyroid Gland releases______
Calcitonin to decrease blood Calcium levels
When there's Low Blood Calcium levels, Parathyroid Gland releases______
Parathyroid Hormone (PTH) to increase blood Calcium levels
In the Proximal Tubule, the trasnporter for Calcium reabsorption is UNKNOWN
What part of the Nephron has the most PTH receptors?
Majority of Calcium reabsorption is where in the Nephron?
Proximal Tubule. 60%
Impact of PTH at the Distal Tubule
Increases Calcium channels on Apical membrane
Increases Calcium ATPase on Basolateral Membrane
Overall, more Calcium reabsorption
Sequence of events for Hypocalcemia
Parathyroid releases PTH...Increases Calcium levels..Calcium resorption by Bones.. Increases Blood Calcium levels
Parathyroid releases PTH...Activate Vitamin D..Calcium reabsorption by GI system..Increases Blood Calcium levels
Aldosterone at the Distal Tubule/Collecting Duct impacts what?
Increases NaCl, water reabsorption
Increases K+ secretion
ADH at the Proximal Tubule, Distal Tubule, Collecting Duct impacts what?
Increases NaCl, water reabsorption
Increases H secretion
ANP (ANF) at the Distal Tubule/Collecting Duct impacts what? ANP = Atrial Natriuretic Peptide/Factor
Decreases NaCl reabsorption thus, Decrease Blood Volume
PTH at the Proximal Tubule, Thin/Thick Ascending Loop of Henle, Distal Tubule impacts what?
Increases Ca reabsorption