Renal Physl 6 Flashcards
What do renal functions like glomerular filtration depend on?
Renal blood flow
What is renal blood flow modulated by?
Systemic pressure
What do renal sympathetic nerves do?
They terminate on renal vasculature and extend to the renal tubules and participate in renal blood control and tubular function
What does increased renal sympathetic activity do?
Decreases RBF and GFR
How does renal sympathetic activity decrease RBF and GFR?
It causes vasoconstriction causing changes in glomerular hydrostatic pressure
What happens if glomerular hydrostatic pressure increases?
GFR increases
What is renal auoregulation?
The mechanisms that exist to stabilize renal blood flow and GFR
What are the two mechanisms involved in autoregulation?
- Myogenic response
* Tubuloglomerular feedback mechanism (TGF)
Why is RBF and GFR relatively stable over a wide range?
Due to the myogenic response and TGF
What occurs in the Myogenic response?
Smooth muscle of glomerular afferent arterioles stretch as blood pressure and renal blood flow increases stretch sensitive ion channels open and the muscle cells depolarize causing opening of voltage gated calcium channels which induces vascular smooth muscle contraction increasing vasoconstriction stabilizing GFR
What happens in the myogenic response if blood pressure and renal blood flow decrease?
The resting contraction of the afferent arteriole is decreased so the blood vessel becomes dilated and restores glomerular hydrostatic pressure
What is the range of BP that the myogenic response can occur?
80 mmHg and 180 mmHg
What does active constriction of the efferent arteriole do?
Causes blood to back up into the glomerular capillaries increases glomerular hydrostatic pressure of GFR
What is TGF?
A local control mechanism where the rate of fluid flowing through parts of the tubule can initiate changes in renal blood flow which helps to stabilize GFR
What passes between the efferent and efferent arteriole?
- Ascending limb of the loop of henle
* Distal tubule
What is the Juxtaglomerular apparatus?
The point where the distal tubule makes contact with the afferent and efferent arteriole
Where are the macula densa located?
In the wall of the distal tubule
What has juxtaglomerular cells?
The portion of the afferent arteriole making contact with the macula densa
What do the juxtaglomerular cells secrete?
Renin
How does the TGF system work with increased GFR?
- GFR increases and the macula densa sense an increased delivery of sodium and chloride
- Macula densa release a paracrine factor
- Paracrine factor acts on neighboring arterioles causing vasoconstriction and reduces blood flow
How does the TGF system work when GFR falls as a result of a drop in arteriole pressure and renal blood flow?
Paracrine factor elicits dilation of the afferent arteriole. A factor from the macula densa also triggers renin release which forms angiostenosis two causing vasoconstriction increases glomerular hydrostatic pressure
