What is one of the fastest ways to lower high blood pressure in the body?
Excrete excess fluid from the plasma.
Define autoregulation.
A process by which the kidneys limit changes in GFR in response to MAP.
True or false?
Small changes in MAP have large effects on GFR.
False, due to the presence of autoregulation.
What is the optimal MAP range at which the kidneys can successfully autoregulate GFR?
75 - 140 mmHg.
What is the location and function of the macula densa?
1.) Location: epithelial cells of the distal tubule.
2.) Function: to monitor the NaCl concentration of the filtered plasma (an indicator of GFR), and communicate with juxtaglomerular cells if a change is needed.
What is the location and function of juxtaglomerular cells?
1.) Location: at the vascular entrance and exit of the glomerulus on the afferent and efferent arteriole, respectively.
2.) Function: upon receiving signals from the macula densa, the juxtaglomerular cells (at the afferent arteriole) modulate their release of renin.
What is angiotensinogen?
An inactive hormone produced by the liver that circulates through the body.
A good vasoconstrictor.
Describe the process - in order - that occurs when renin is released from the afferent arteriole juxtaglomerular cells.
1.) Angiotensinogen circulating in the blood is converted to Angiotensin 1 as it comes into contact with renin.
2.) Angiotensin 1 is converted to Angio. 2 as it comes into contact with ACE in the glomerulus.
3.) The AT receptors of the efferent arteriole bind the Angio. 2 and constrict.
What happens to GFR when the efferent arteriole binds Angiotensin 2?
The efferent arteriole constricts, causing an increase in resistance and therefore a backup of fluid in the glomerulus.
The increased fluid causes and increase in capillary hydrostatic pressure Pc, leading to an increase in GFR.
Describe the negative feedback loop that occurs if GFR is too high.
1.) The macula densa senses an increase in fluid volume in the distal tubule as well as a high concentration of NaCl.
2.) If signals the juxtaglomerular cells to stop releasing renin.
3.) The efferent arteriole relaxes, and GFR decreases.
Without autoregulation, how will the following events affect GFR?
1.) MAP increases
2.) Afferent arteriole resistance increases
3.) Efferent arteriole resistance increases
1.) GFR increases
2.) GFR decreases
3.) GFR increases
How will the following hormones affect GFR?
1.) Norepinephrine
2.) Epinephrine
3.) Endothelin
4.) Nitric Oxide
5.) Prostaglandins
1.) Vasoconstrictor - GFR decreases
2.) Vasoconstrictor - GFR decreases
3.) Vasoconstrictor - GFR decreases
4.) Vasodilator - GFR increases
5.) Vasodilator - GFR increases
True or False?
Without autoregulation, small changes in MAP can have huge effects of GFR and urine output.
True.
Describe how an increase in MAP will effect the myogenic response of the afferent arteriole.
1.) MAP increases and stretches arteriolar wall
2.) Stretch-activated Ca2+ channels open
3.) Ca2+ influx
4.) Smooth muscle contracts
5.) Pc decreases --> GFR decreases
True or False?
The myogenic response is a positive feedback loop.
False.
True or False?
The renin - angiotensinogen process affects both the afferent and efferent arterioles.
False.
Since the conversion of angiotensinogen to angio. 2 occurs after the afferent arteriole, endothelial derived Nitric Oxide is released [locally?] as a vasodilator, and the myogenic response acts as its vasoconstrictor.
True or False?
The renin-angiotensinogen process only occurs locally at the kindeys.
False.
As renin is released from the juxtag. cells in response to low GFR (from low MAP), some renin ultimately converts angiotensinogen to angio. 2 all over the body, causing broad constriction of blood vessels and thus increasing MAP.
The afferent arteriole mostly affects the (glomerular/peritubular) capillaries, while the efferent arteriole mostly affects the (glomerular/peritubular) capillaries.
1.) Glomerular
2.) Peritubular
Which of the following solutes are not completely reabsorbed into the plasma once they have been filtered?
1.) Glucose
2.) Bicarbonate
3.) Urea
4.) Chloride
5.) Sodium
Urea, a byproduct of amino acid metabolism.
Key Concept # 3
How do you calculate Filtered Load?
Filtered Load = GFR x [substance]plasma
True or False?
The membrane composition of tubular epithelial cells is relatively uniform.
False.
Tubular epithelial cell membranes are polarized, with distinctly different compositions existing at the apical, and basolateral sides.
What is the ultimate fate of any fluid or solute not reabsorbed through the tubular membrane and into the peritubular capillaries?
Excretion in the urine.
The interstitium between the tubule and peritubular capillaries is similar in composition to _________.
Plasma - with the exception of proteins.
Why do the peritubular capillaries have a much larger IIpc than normal?
Why is this significant?
As plasma was filtered from the glomerular capillaries, [protein] increased and thus the IIGC.
This higher IIGC causes net absorption into the peritubular capillaries once fluid has entered the interstitium.
True or False?
Passive diffusion and active transport are relatively instant processes.
False.
A solute must move, find and bind to a carrier/pore. The longer there is exposure the better.
In regards to glucose filtration and reabsorption, at what point on the reabsorption curve does glucose begin to be excreted in the urine?
At the transport maximum, TM.
At this point, all of the glucose transporters (Na/Glu symport), are saturated.
Glucose is transported from the tubule lumen into tubular epithelial cells by _________.
Secondary active transport of the Na+/Glucose symporter.
On which surface of a tubular epithelial cell are you likely to find passive carriers and leak channels?
The apical membrane that faces the tubular lumen.
On which surface of a tubular epithelial cell will you find many Na+/K+ pumps?
