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Glomerular Filtration
Activity 1:  Effect of Arteriole Diameter on Glomerular Filtration

1.   Compare this data with your baseline data.  How did increasing the afferent arteriole radius affect glomerular filtration rate?
>>Increasing the afferent arteriole radius pushed the glomerular pressure, the glomerular filtration rate, and the volume of urine to be higher than the baseline data. Increasing the afferent arteriole radius increased the glomerular filtration rate.
2.   Under these conditions, does the fluid flow through the nephron?
>>No! No urine was collected which indicates no fluid flows through the nephron. 

3.   What is the glomerular filtration rate?
>>The glomerular filtration rate is 0 which means the glomeruli are not carrying out any filtration task. 
4.   How does it compare to your baseline data, and why? 
>>The glomerular filtration rate in baseline data is 124.99 which indicate functional glomeruli. The data support the concept that the reduction of the size of the afferent radius will definitely affect the glomerular filtration functions. With significant reduction of the afferent radius, very limited blood can pass through the capillaries and that leaves insufficient fluid to be filtered no any extra water can be produced as urine.     
5.   How did increasing the efferent radius affect glomerular filtration rate? 
>> Increasing the efferent radius decreases the glomerular filtration rate. Increasing the efferent radius allows more blood drainage out of the glomerulus and that decreases the amount of blood to be filtered so the glomerular filtration rate will decrease.   

6.   How did decreasing the efferent radius affect glomerular filtration rate? 
>> Decreasing the efferent radius increases the glomerular filtration rate. The constriction of the efferent radius will limit blood drainage out of the glomeruli and that requires increasing the glomerular filtration rate. More blood in the glomeruli means more work, so the job has to be done faster.     

7.   Physiologically, what could be the cause of a change in afferent or efferent arteriole radius? 
>>The sympathethic impulses largely play major roles in changing the afferent or efferent arteriole radius. The afferent or efferent arteriole radius can dilate or constrict depending on the impulses generated by the sympathetic nerves keeping the autonomic control of blood flow depending on the concentration levels of the body electrolytes and metabolic wastes which are the main basis of blood flow autoregulation. Increased sympathetic impulses will cause afferent and efferent arteriole to vasoconstriction while decreased sympathetic stimulation will facilitate vasodilation. The mechanisms involve various hormones and electrolytes and are largely dependent on the amount of metabolic activity, the extrinsic control mechanism depending on the perfusion needs of the cells, and the vascular resistance generated by the blood pressure. The amount of body fluids and the levels of body wastes definitely play critical physiologic roles that cause changes in the afferent or efferent roles. The effects of drugs play significant roles as well.     

Activity 2:  Effect of Pressure on Glomerular Filtration

1.   As pressure increased, what happened to the pressure in the glomerulus? 
>>As pressure increased, the pressure in the glomerulus also increased.

2.   What happened to the glomerular filtration rate? 
>>The glomerular filtration rate kept on increasing with gradual increase of the pressure. 
3.   How did the urine volume change? 
>>The urine volume also increased.

4.   How could increased urine volume be viewed as being beneficial to the body?
>>With increased urine volume, more filtrates mostly salts which are body wastes will be excreted and that lessens the potential harmful effects of fluid retention and accumulation of unnecessary wastes in the body.   

Activity 3:  Combined Effects

1.   What happened to the glomerular filtration rate and urine volume after you reduced the pressure? 
>>Both decreased.

2.   How could you adjust the afferent or efferent radius to compensate for the effect of the reduced pressure on glomerular filtration rate and urine volume?  Use the simulation to determine your answer. 
>>Increase the afferent radius or decrease the efferent radius.

3.   What changes are seen in nephron function when the valve is closed?
>> There was no glomerular filtration rate and no urine production.     

4.   Why were these changes seen?>> When the valves are closed simulating blocked collecting ducts, the built up pressure caused by the increased solute volume opposes the forces driving up the filtration tasks of the kidney. The nephrons could burst if the filtering task is continued so the kidney is just trying to save ‘itself. 

5.    Is the kidney functional when the glomerular filtration rate is zero?  Explain your answer.
>>No. When glomerular filtration rate is zero, it means nothing is filtered. The kidney is dormant and not carrying out any upfront task to stay functional.

6.   What is the major “ingredient” that needs to be removed from the blood?
>>Urea along with different metabolic salts. 

7.   Studies on aging have demonstrated that some nephrons may fail as we get older.  Will this be a problem regarding urine formation?
>>Aging causes inevitable physical and physiological degenerations and the renal system is not exempted from that normal change. About half of the million nephrons start to die and fail to function but the rest remain their activities. The decline of the number of functional units may cause slowing of the renal functionalities including the glomerular filtration rate. The glomerular filtration rate decreases and that will definitely decrease the urine formation but as long as the remaining nephrons are functional urine formation will not be a problem. The other physiological functions particularly the metabolic functions of the body also decline with age and that can significantly decrease the workload of the nephrons. The decrease in he volume of urine therefore is physiologic and not a pathologic issue unless others problems are involved.       

      8. If blood pressure went down – for example, as the result of blood loss – what    changes would the kidney need to make to maintain its normal filtration rate? 
>>The kidney needs to control the vasodilation of the efferent arteriole radius and the vasoconstriction of the efferent radius through the autoregulation and autonomic control mechanisms. The kidney will need to increase its reabsorption capability by getting more ADH. The kidney will also need to increase the blood input which can be practically accomplished through blood transfusion and fluid hydration or increasing the body fluid intake orally or intravenously. The kidney may also need reinforcement with the use of the drugs to temporarily enhance fluid retention and reabsorption while keeping the levels of solutes and electrolytes controlled.     

Simulating Urine Formation
Activity 4:  Effect of solute Gradient on Urine Concentration

1.   How did the urine solute concentration change as the concentration gradient of the interstitial fluid increased? 
>>The urine solute concentration also increased with the same values as the concentration gradient.

2.   What happened to the urine volume as the concentration gradient increased?   Why?>>The urine volume decreased and that could be because more water is driven out of the urine and reabsorbed as concentration gradient increases.

3.   By increasing the concentration gradient, what are you doing to the urine that is formed? 
>>Increasing the solute concentration in the urine and that makes the urine formed very concentrated.
4.   Predict what would happen to urine volume if you did not add ADH to the collecting duct. 
>>The urine volume will significantly increase since there is no enhancement of water permeability in the collecting duct and the distal tubule so less water will be reabsorbed. The less water reabsorbed, the more urine will be formed.   

Activity 5:  Reabsorption of Glucose

1.   What happens to the glucose concentration as you add glucose carriers to the system? 
>>The glucose concentration decreases because the carriers will be able to carry the glucose across the walls of the glomerulus for reabsorption. 

2.   At what point does the glucose concentration in the urine become zero? 
>>In the experiment, glucose in the urine become zero when 400 glucose carriers were added which means adding enough glucose carriers will facilitate reuptake of the glucose leaving nothing in the unabsorbed water formed as urine.     

3.   What would you expect to find in the urine of a diabetic?  Why?
>>Urine of the diabetic will have high glucose concentration. Due to lack of the glucose carriers relatively less than the amount of glucose to be transported, high amount of glucose could not be carried across leaving high concentration discarded with the urine formed.   
Activity 6:  Effect of Hormones on Reabsorption

1.   Which hormone has the greater effect on urine volume?  Why?
>>The ADH has greater effect on urine volume since it caused dramatic decrease in its mount. DH increases the water permeability of the distal tubule and the collecting ducts thus more water will be reabsorbed making the urine volume less within regulated levels that can keep the water balance. Aldosterone caused just slight decrease in the urine volume. 

2.   How does the addition of aldosterone affect the concentration of potassium in the urine? 
>>Addition of aldosterone slightly increased the potassium concentration in urine which is an indication that the hormone has facilitated reabsorption of potassium. 
3.   How does the addition of ADH affect the concentration of potassium in the urine?
>> Potassium concentration in urine significantly increased to almost 10x.

4.   How does this compare to the effect of adding aldosterone, with respect to potassium concentration in the urine?
>>Adding aldosterone increases the potassium concentration less than two folds much lower than the ten folds concentration increase with the addition of ADH. That means aldosterone has the capability to spare some potassium for reabsorption while ADH cares less about keeping it.   
5.   How does the addition of both hormones affect 1) urine concentration, 2) urine volume, and 3) potassium concentration?
>> Addition of aldosterone does not change the urine concentration but slightly decreases the urine volume and slightly increases the potassium concentration.
Addition of ADH significantly increases the urine concentration and the potassium concentration while significantly decreases the urine volume.
Addition of both hormones increases the urine concentration and the potassium concentration while the significantly decreases the urine volume as the agonistic effects of both from their similar effects.   
6.   If ADH were not used, how would the urine concentration vary?  Explain your answer.
>>If ADH were not used, the urine concentration will largely depend on the volume and the osmolality of the plasma coming in to the system for filtration. Without ADH, reabsorbtion of fluids will not be facilitated so it means more fluid intake will yield more fluid output and that will result to a diluted urine. In contrast, when the amount of fluid to be filtered is less, the urine will become concentrated. The solute concentration in the urine will also depend on the solute concentration gradient of the interstitial fluid which means the urine concentration could largely depend on the kind of foods and fluids intake.
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topic author
4 years ago
Great post and good answers thanks for sharing the knowledge.
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