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Urine formation

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Urine formation

Postby chikis » Tue Nov 08, 2011 2:42 pm

Am I want to post this question in form of objective.So any person who want to answer the question should choose the correct answer from the options provided and do well to explain how the option he/she has chosen is true. So here is the question: which of the following statements on urine production is not correct? A. Concentrated urine is produced under the control of antidiuretic hormone. B. The total volume of urine produced depends on the need for water excretion. C. If there is an excess intake of water, dilute urine is excreted. D. If there is a shortage of water in the body the volume of urine produced decreases. E. In the presence of antidiuretic hormone dilute urine is produced. So which is the correct answer and why?
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Postby aptitude » Wed Nov 09, 2011 2:51 am

E is incorrect. The functions of antidiuretic hormone, as the name implies, serve to prevent water loss and dehydration, and therefore ADH will reabsorb sodium from the distal tubule, and water will follow by osmosis. Therefore, in the control of ADH, concentrated urine is produced, not dilute urine.
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Re: Urine formation

Postby chikis » Wed Nov 09, 2011 5:23 am

@aptitude, thank you for your answer. You have tried very well. But one more thing, you could have studied the question very well before answering. In the option I provided, I said that all the ' all the following are correct about urine production except one'; so which one is not true about urine formation? Since almost all my options are true about urine formation, I require you to give me the one that is not true about urine formation with reason.Thank You.
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Postby chikis » Wed Nov 09, 2011 7:41 am

@aptitude, if you say that E. is your answer, that means you agree the option A to D is true for urine formation except E. which is not. Or is that not what you mean?
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Re:

Postby JackBean » Wed Nov 09, 2011 6:00 pm

aptitude wrote:E is incorrect.

I guess this is what he meant

and how nicely you're asking us to do your homework, aren't you?
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Postby chikis » Thu Nov 10, 2011 5:52 am

@Jackbean ,not exactly, I just want to be sure. Although, I will still go for further research in other to acertian the correctness of the answer. Thank you.
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Re: Urine formation

Postby daniel.kurz » Mon Nov 14, 2011 4:23 am

chikis wrote:@aptitude, thank you for your answer. You have tried very well. But one more thing, you could have studied the question very well before answering. In the option I provided, I said that all the ' all the following are correct about urine production except one'; so which one is not true about urine formation? Since almost all my options are true about urine formation, I require you to give me the one that is not true about urine formation with reason.Thank You.


Aptitude is correct, and you are quite wrong.
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Re: Urine formation

Postby chikis » Mon Nov 14, 2011 12:35 pm

My sincere gratitude goes to Aptitude, JackBean and Daniel.kurz for their imense contribution to this post. It also goes to any other member that may contribute to the post in future.
Two heads are better than one. When scientist put heads together, problems are solved; knowledge is developed, things work out fine and life become improved.
In the course of my preparation for an exam, I came across this very question in a prepared past question and answers of the said exam. I studied the question and analysed it hastely; my mind was twisted between two of the options A and E.
I then turned to the answer page of the book and suprisingly found A to be the answer and I wonder why and how; I become confused and burdened.
That burden I cannot carry alone and I decided to bring it foward so that other biologists can discuss it. When it landed in the forum, You my fellow scientist lambasted me for bringing in such question without working on it before posting it but I did in my own little way which showed no succes to me.
Nevertheless, your critics has made me go back to the drawing board to get a better picture of what I painted initialy. In the course my re-evaluation of the question and your opinions, I found that Aptitude is right indeed. Kudos to Aptitude for his careful answer! Thank you Aptitude. Below is a brief of what I found out cocerning the question
:The amount of water saved and the final concentration of the urine depend on the permeability of the walls of the collecting duct. When the blood osmotic pressure increases, as duringg dehydration, more ADH is released from the pituitary gland. ADH increases the permeability of the collecting duct probably by expanding the size of pores of the walls of the duct. Then, as the fluid in the collecting duct passes through the hyperosmotic region of the kidney medulla, water diffuses through the pores into the surounding interstitial fluid and is carried away by the blood circulation. The urine looses water and become more concentrated. Given this sequence of events for dehydration, it is not difficult to anticipate how the system respond to overhydration: the pituitary stops releasing ADH, the pores in the collecting duct walls close, and a large volume of dilute urine is excreted.
The above brief account for urine formation could not have been possible if no body replied or considered my question because I will feel that the question is so difficult such that it is rare to have an answer to it.
From the above account I now conclude that the option A in past question and answer is wrong but that the correct option is E. Which Aptitude earliar wrote.
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