TBR v. Textbook: Constriction of Efferent Arteriole in Kidney

[justadream]

My question regards the effects of constricting the efferent arteriole (in the region of the glomerulus). TBR (page 180 book I #41) claims that constricting the efferent arteriole will first INCREASE and later DECREASE* the glomerular filtration rate.


A textbook I am looking at (Silverthorn physio 6th ed) says that constricting the efferent arteriole will INCREASE the glomerular filtration rate.



So for MCAT purposes, if asked what will happen by constricting the efferent arteriole, what should the answer be if it is unclear whether the question is referencing short-term but long-term effects?



*TBR says this decrease will occur because more plasma will eventually accumulate in Bowman’s capsule. This plasma will increase the solute concentration in the glomerulus and inhibit fluid trying to flow out of the glomerulus.

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[Czarcasm]

My question regards the effects of constricting the efferent arteriole (in the region of the glomerulus). TBR (page 180 book I #41) claims that constricting the efferent arteriole will first INCREASE and later DECREASE* the glomerular filtration rate.


A textbook I am looking at (Silverthorn physio 6th ed) says that constricting the efferent arteriole will INCREASE the glomerular filtration rate.



So for MCAT purposes, if asked what will happen by constricting the efferent arteriole, what should the answer be if it is unclear whether the question is referencing short-term but long-term effects?



*TBR says this decrease will occur because more plasma will eventually accumulate in Bowman’s capsule. This plasma will increase the solute concentration in the glomerulus and inhibit fluid trying to flow out of the glomerulus.

A very similar question was asked a few days ago: http://forums.studentdoctor.net/threads/glomerular-filtration-rate.1077605/ Might find that helpful.

 

[IslandStyle808]

My question regards the effects of constricting the efferent arteriole (in the region of the glomerulus). TBR (page 180 book I #41) claims that constricting the efferent arteriole will first INCREASE and later DECREASE* the glomerular filtration rate.


A textbook I am looking at (Silverthorn physio 6th ed) says that constricting the efferent arteriole will INCREASE the glomerular filtration rate.



So for MCAT purposes, if asked what will happen by constricting the efferent arteriole, what should the answer be if it is unclear whether the question is referencing short-term but long-term effects?



*TBR says this decrease will occur because more plasma will eventually accumulate in Bowman’s capsule. This plasma will increase the solute concentration in the glomerulus and inhibit fluid trying to flow out of the glomerulus.

It all depends on the answer stems given. You want the answer that 1) relates to what is being asked in the question stem 2) the most complete answer. The filtration rate increasing and then decreasing is the complete answer.

However, before you start thinking that this is all you need to remember, I will tell you this. You need to understand how all of this is working in a dynamic system. Why does the pressure decrease after some time? What does the kidney or even the body do in order to decrease the filtration rate? By having this background, you will better be able to discern the best answers from the worst (remember it is just as much about knowing the wrong answers as much as it is knowing the best answer).

As you have seen in the previous thread (linked by Czarcasm), my explanation comes from that background understand. With this understanding, you can tackle on various problems from more angles than you can imagine. When you get a problem wrong, don't just look up the answer, make sure you grasp the overall concept (in this case how the kidney regulates filtration).

Good luck to you!