Renal System Physiology 2 - Teel Flashcards
Renal Blood flow (RBF) ratios in cortex and medulla
RBF = __% cardiac output
90% to cortex, 10% to medulla
20% cardiac output
Changes in renal blood flow and renal plasma flow affect GFR
When Ra increases (resistance of afferent arterioles), what happens to renal blood flow?
When Re increases (resistance of efferent arterioles), what happens to renal blood flow?
Ra increasing = afferent arterioles are constricting, causing a decrease in renal blood flow.
GFR then decreases due to decreased PG (pressure from glomerulus)
Re increasing = efferent arterioles constricting, causing buildup of pressure before, which is where glomerulus is. GFR and PG both increase. Renal blood flow still decreases.
How to measure Renal Plasma Flow?
PAH is in the blood, gets filtered, it is not reabsorbed, gets secreted, 100% clearance. If this happens then we have an indicator of Renal Plasma Flow.
The clearance PAH is an estimate of renal plasma flow. (responsible for GFR)
Tubuloglomerular feedback (TGF)
increase renal arterial pressure = increase RBF = increase GFR = increase of NaCl to macula densa cells
Response: vasoconstriction of afferent arterioles = decrease RBF = decrease GFR = decrease delivery of NaCl to macula densa cells
Factors affecting RBF and GFR:
Angiotensin II
Catecholamines
Arginine vasopressin (AVP)
Atrial natriuretic peptide (ANP)
Angiotensin II : decrease RBF and decrease GFR
Catecholamines : decrease RBF and decrease GFR
Arginine vasopressin (AVP) : decrease urine output
Atrial natriuretic peptide (ANP) : increase RBF and increase GFR
What is the Glomerulotubular balance concept, and what are some things that stimulate reabsorption?
Glomerulotubular balance concept: reabsorbing a relatively constant fraction of some sort of filtered sodium load.
Aldosterone stimulates reabsorption of Na+ by upregulating ENACs and Na/K exchange
Adrenergic stimulation increases reabsorption of Na+ by upregulating Na/H & Na/K exchange
AVP stimulates reabsorption of Na+ in TAL and principal cells of cortical collecting ducts
ANP increases excretion of Na+ by increasing RPF / GFR which increases Na load delivered to distal tubules.
Paracellular Transport
Transcellular Transport
Paracellular: between adjacent tubular cells. Most of reabsorption of Cl here in proximal tubules & cortical collecting ducts
Transcellular: Cl by : Across apical membrane / basolateral membrane.
In thick ascending limb (TAL) of hindley’s loop, 1 specific transporter that transports 3 different ions.
Na/K/2Cl all go in same direction. Cotransport, not exchange
Renal Handling of Urea and Water
Where is Urea filtered/ reabsorbed and how?
Urea freely filtered at glomerulus. Reabsorbed from inner medullary collecting ducts into medullary interstitium and loops of Henle.
Urea is a solute and water tends to follow it.
Renal Handling of Solutes
How is phosphate reabsorbed?
Filtered phosphate is 80% reabsorbed in proximal tubules via cotransport with Na+
Difference between cotransport and exchange
Cotransport: same direction
Exchange: opposite direction
Renal Handling of Solutes
How is calcium reabsorbed?
more than 1/2 of filtered Ca2+ reabsorbed paracellularly in proximal convoluted tubules.
Reabsorption stimulated by PTH and Vit. D3
Renal Handling of Solutes
How is Mg2+ reabsorbed?
About 70% of filtered Mg2+ reabsorbed in TAL. (NOT PROX CONV TUBULE)
Reabsorption is largely unaffected by Vit. D3
Which cells reabsorb / secrete K+
a-intercalated cells reabsorb K+.
Principal cells secrete K+
Renal Handling of Solutes
How is K+ reabsorbed/filtered?
Reabsorption of filtered K+ is paracellular in proximal tubules.
Cotransport is via Na/K/2Cl in TAL (reabsorption). a-intercalated cells reabsorb K+. Principal cells secrete K+
Freely filtered
Hormones that help potassium levels in blood
Insulin, Aldosterone, Epinephrine allow Dietary K+ absorbed from gut into blood.
Hypokalemia vs Hyperkalemia
Hypokalemia: not enough potassium in blood
Hyperkalemia: high potassium levels
What happens when you increase potassium intake?
Increased K+ intake -> increased plasma K concentration -> increased aldosterone -> increased k secretion cortical collecting tubules -> increased k excretion
Renal Handling of Glucose
How is it reabsorbed?
How is it filtered?
Reabsorbed in proximal tubule via apical SGLT1 & 2 and basolaterally via GLUT1 and GLUT2.
Glucose normally 100% reabsorbed.
Freely filtered
Filtered load:
Plasma concentration x GFR
Renal Handling of Glucose
Relationship between filtered load, reabsorption, excretion
Filtered load = linear. As plasma concentration increases, so does filtered load of glucose.
Reabsorption of glucose: stabilizes due to transporters overloading. Originally increases as plasma conc. and filtered load increases, but will start to stay in blood glucose.
Excretion: Nothing in beginning, but if you have too much glucose, will start to excrete. Glucose in urine now. Normal until around 280 mg/dl
Theres only so much glucose u can reabsorb. Once transporters in proximal tubule become saturated, it starts to appear in your urine.
Renal handling of protein, oligopeptides, and AAs
Proximal tubular cells remove filtered protein by endocytosis
Apical membrane H+ oligopeptide cotransporters remove oligopeptides
Proximal tubular cells reabsorb filtered AAs by Na+ dependent / Na+ independent mechanisms.
