Renal Recap Flashcards
Label the Nephron
What is the difference between the Principal Cells and Intercalated Cells in the CD?
Principal cells have a few mitochondria, mostly function for NaCl reabsorption and K secretion.
Intercalated cells have a lot of mitochondria and function in acid-base regulation. Some IC secrete H+, some secrete HCO3-
What is the structure of the juxtaglomerular apparatus?
macula densa of thick ascending LH + extraglomerular mesangial cells + granular cells of afferent arteriole (manufacture, store, and secrete renin)
What is the function of the juxtaglomerular apparatus?
sense Na/pressure, involved in autoregulation of renal blood flow, GFR, systemic BP control
Increase in afferent arteriole pressure 🡪 increased glomerular pressure 🡪 increased GFR.
Increased Na/K delivery to macula densa 🡪 decreased renin. And viceversa.
Within what range of systemic BP is the (healthy) kidney able to provide auto-regulation of renal blood flow?
80-180 mmHg
What happens to renal blood flow and GFR with dilation of the afferent arteriole?
RBF: up
GFR: up
What happens to renal blood flow and GFR with Constriction of the afferent arteriole?
RBF: down
GFR: down
What happens to renal blood flow and GFR with Dilation of the efferent arteriole?
RBF: up
GFR: down
What happens to renal blood flow and GFR with constriction of the efferent arteriole?
RBF: down
GFR: up
Name the 3 main renal transport mechanisms:
- Passive transport (diffusion)
- Active transport
- Endocytosis
Describe passive transport (diffusion)
Movement down a concentration gradient or electrical gradient.
Includes solvent drag (movement of ions with water even if not with concentration gradient) and Facilitated diffusion (passive, but requires transport protein- uniport, smport, antiport, or secondary active transport)
Describe Active transport
coupled directly with energy (ATP)
Describe endocytosis
movement by invagination of plasma membrane, does require ATP
Draw and explain the basic mechanisms of electrolyte reabsorption/secretion in the kidneys.
This does not have to be a specific site or electrolyte.
- Active transport at the basolateral membrane (3Na/2K/ATPase pump) creates a gradient (Na out of cell into interstitium, K into cell)
- Passive transcellular transport at the luminal membrane driven by concentration gradient, partially created by the active pump (cotransporters, antitransporters) and partially created due to lower concentration of electrolytes in blood (highly filtered at glomerulus)
- Paracellular transport driven by transepithelial (transmembrane) potential difference (electrical charge)- lumen positive or lumen negative
Paracellular solute drag along with water (aids with reabsorption) - “Sink” effect from rapid tubular flow (aids excretion)
What is the PRIMARY function of the proximal tubule?
reabsorption of most water (67%) and solutes (Na, Cl, K, glucose, AA’s) linked to Na/K ATP-ase pump in basolateral membrane
What is the PRIMARY function of the thin descending LH?
H20 reabsorption through aquaporins with NO NaCl
What is the PRIMARY function of the thin ascending LH?
Na/Cl reabsorbed through passive diffusion, NO H20
What is the PRIMARY function of the Thick ascending LH?
Reabsorption of solutes via Na/K/ATPase in basolateral membrane. NO H20. “Diluting segment”- solutes out of tubule, H2O stays in.
What is the PRIMARY function of the distal tubule?
“Adjustment” of lytes but impermeable to H20
What is the PRIMARY function of the late distal tubule and the CD?
Principal cells: reabsorb Na/H2O, secrete K
Intercalated cells:
— α-intercalated cells secrete H+, reabsorb HCO3- and K+
— β-intercalated cells secrete HCO3-, reabsorb H+ and Cl-
Angiotensin II:
Major stimulus:
Nephon site of action:
Effect on transport:
Major stimulus: ↑ Renin
Nephon site of action:
Proximal tubule
Thick ascending limb
Distal tubule /Collecting duct
Effect on transport: ↑ NaCl and H2O reabsorption
Aldosterone
Major stimulus:
Nephon site of action:
Effect on transport:
Major stimulus: ↑ Angiotensin II
↑ [K+]p
Nephon site of action:
Thick ascending limb
Distal tubule /Collecting duct
Effect on transport: ↑ NaCl and H2O reabsorption
ANP, BNP, urodilatin
Major stimulus:
Nephon site of action:
Effect on transport:
Major stimulus: ↑ ECFV
Nephon site of action: Collecting duct
Effect on transport: ↓ H2O and NaCl reabsorption
Uroguanylin, guanylin
Major stimulus:
Nephon site of action:
Effect on transport:
Major stimulus: Oral ingestion of Nacl
Nephon site of action:
Proximal tubule
Collecting duct
Effect on transport: ↓ H2O and NaCl reabsorption
Sympathetic nerves
Major stimulus:
Nephon site of action:
Effect on transport:
Major stimulus: ↓ ECFV
Nephon site of action:
Proximal tubule
Thick ascending limb
Distal tubule /Collecting duct
Effect on transport:↑ NaCl and H2O reabsorption
Dopamine
Major stimulus:
Nephon site of action:
Effect on transport:
Major stimulus: ↑ ECFV
Nephon site of action: Proximal tubule
Effect on transport: ↓ H2O and NaCl reabsorption
ADH/AVP
Major stimulus:
Nephon site of action:
Effect on transport:
Major stimulus:
↑ Posm
↓ ECFV
Nephon site of action: Distal tubule /Collecting duct (aquaporins)
Effect on transport:↑ H2O reabsorption
Briefly explain RAAS
- Juxtaglomerular cells in the afferent arterioles synthesize and secrete renin
- Renin secretion is stimulated when:
– Perfusion pressure to the kidneys is reduced
– Sympathetic innervation to the kidneys is activated
– NaCl delivery to the macula densa is decreased - Renin converts Angiotensinogen (produced by liver) 🡪 Angiotensin I
– AT I 🡪 AT II by ACE in the kidneys and lungs
– AT II stimulates aldosterone secretion, vasoconstricts arterioles, stimulates ADH + thirst, and enhances NaCl reabsorption by the kidneys