1.3.1 Glomerular Filtration Function and Renal Blood Flow II Flashcards
How does dilation of efferent arterioles affect blood flow resistance, RBF, and glomular capillary pressure? What is the net effect on GFR?
Decrease blood flow resistance
Increase RBF (tends to increase GFR)
Drop in glomerular capillary pressure (tends to decrease GFR)
Net effect: Small drop in GFR
Between which arterial pressures does RBF and GFR remain fairly constant?
90 and 180 mm Hg
What are some of the extrinsic regulators of RBF and GFR?
Sympathetic nerves
Humoral factors (ANG II, prostaglandins, NO, bradykinin, endothelin, adenosine)
What are the two mechanisms through which renal blood flow is autoregulated?
- The myogenic response
- The tubuloglomerular feedback
Describe the cellular mechanism of ANG II action on the adrenal glands.
ANG II binds AT1 on the surface of the adrenal cell. This activates PLC which produces IP3 and DAG. These two cellular factors work to increase Ca and PKC. The net effect in the activation of txn factors and aldosterone synthesis.
Describe the cellular mechanism of ANG II on SM cells of vessels.
ANG II binds AT1 on the surface of SM cells. This stimulates PLC to produce IP3 and DAG. These two pathways act to increase the Ca++ within the SM cell resulting vasoconstriction
The myogenic response mainly involves which type of arteriole?
Afferent
How does dilation of afferent arterioles affect blood flow resistance, RBF, and glomular capillary pressure? What is the net effect on GFR?
Drop in blood flow resistance
Rise in RBF
Rise in glomerular capillary pressure
Net effect: Increase in GFR
What are some of the other substances produced by the kidney that have an endocrine function?
Prostaglandins: vasodilation, reduce Na+ reabsorption
Kinins: vasodilation
Endothelin: vasoconstriction
Urodilatin: Na+ secretion in collecting ducts
Dopamine: Vasodilation, reduced Na+ reabsorption
What is the normal value for glomerular filtration rate (GFR)?
125 mL/min, 180 L/day
Describe the pathway through which renin leads to vasconstriction, Na+ retention, and Na+ reabsorption in proximal tubules.
How does constriction of efferent arterioles affect blood flow resistance, RBF, and glomular capillary pressure? What is the net effect on GFR?
Increase blood flow resistance
Slows RBF (tends to reduce GFR)
Rise in glomerular capillary pressure (tends to increase GFR)
Net effect: Small rise in GFR
ANG II stimulates the adrenal gland to release what? What effects does this hormone have on Na+ and K+?
The release of aldosterone.
Aldosterone incites Na+ and water absorption while promoting K+ secretion
Describe the cellular mechanisms leading to renin release
Decreased delivery of Na to the macula densa has two effects: inhibits the production/release of adenosine and increases its production of PGE2. The PGE2 passes through the mesangial cells and binds to a receptor on the granular cell of the afferent arteriole. As a result of the decreased adenosine signals and increased PGE2 signals, the granular has reduced calcium leading to the release of renin.
Describe the tone of the artery (dilated, normal, or constricted) at the following pressures: 200, 125, 60?
60: dilated
125: normal
200: constricted
What are some of the stimuli for increased renin release?
Increased sympathetic nerve activity
Decreased renal blood perfusion
Decreased Na delivery to macula densa
Describe the TGF mechanism at the cellular level.
Increased Na and Cl delivery to the macula densa leads to the release of adenosine from the macula densa. The adenosine binds to the A1 receptor on SM cells of the afferent arteriole resulting in an increased in Ca levels. The increased calcium leads to vasoconstriction of the afferent arteriole
When thinking of the kidney as a sprinkler how does constriction of the afferent/efferent arterioles effect the spray?
Draw of the juxtaglomerular apparatus (include renal tubule, macula densa, proximal tubule, glomerular capillaries, afferent arteriole, efferent arteriole, mesangial cells)
What is the equation for GFR?
GFR = KUF * PUF
KUF (includes surface area and permeability)
PUF (net filtration pressure)
What is the mechanistic pathway of the myogenic mechanism?
Increase BP -> Ateriolar SM stretch -> Arteriolar contraction -> Increase resistance -> little change in RBF
Describe the angiotensin effects on renal glomerular arterioles.
What are the systemic effects of the three endocrine substances produced by the kidney (renin, calcitriol, erythropoietin)?
Renin: Vasoconstriction, Na+ retention
Calcitriol: Regulation of Ca and PO4 metabolism
Erythropoietin: RBC production
What is the normal value for renal plasma flow (RPF)?
660 mL/min, 950 L/day
Describe the mechanistic flow of tubuloglomerular feedback.
Increased GFR -> increased tubular fluid flow rate -> increased Na and Cl delivery to macula densa -> increased vasoconstrictor signals (adenosine) -> Increase afferent arteriolar constriciton -> decrease RBF
What is calcitriol?
Active Vit D
What three factors influence ultrafiltration and ultimately the GFR?
Net filtration pressure, surface area, and permeability
What cells release renin?
Granular cells of the afferent arteriole
How does constriction of afferent arterioles affect blood flow resistance, RBF, and glomular capillary pressure? What is the net effect on GFR?
Increases blood flow resistance
Fall in RBF
Fall in glomerular capillary pressure
Net effect: Decrease in GFR
What are the four functions of the mesangial cells?
- Structural support for the glomerular capillaries
- Regulate glomerular filtration via their contractile capacity
- Function as phagocytes
- Secrete paracrine substances
Describe the PGC, GFR, RBF changes in the following circumstances: Afferent constriction, efferent constriction, afferent and efferent constriction, no constriction.
