Question 42

[ckain7170]

I was under the impression that there were several instances where the endocrine system was controlled by stretch receptors, the most obvious being ANP relase by the heart when it is stretched.
Am I mistaken in this thinking?

[jellywing_2058]

Like you said, it is the heart that is being stretched, and the heart is part of the circulatory system!

[bribercar2809]

I believe the endocrine is very much influenced by stretch,

Page 424 Medical Physiology Rhoades

"The receptors for blood volume include stretch receptors in the left atrium of the heart and in the pulmonary veins within the pericardium. More stretch results in more impulses transmited to the brain via vagal afferents and inhibition of AVP release".

This is a direct example of how the endocrine system, depends on stretch receptors. If it were not for this stretch receptor system, the body would have no way to know, when to release AVP, and it would make no difference.

This is very much the same way that the respiratory system works.

Page 378, Medical Physiology Rhoades
"Stretch receptors fire in proportion to the applied transmural pressure, and their usual role is to sense lung volume. "Stimulation of these receptors causes an excitation of the inspiratory off switch and a prolongation of expiration".

This is a similar mechanism, to how the endocrine system works. The receptor detects a stretch, it sends the signal to the brain, and the brain, responds.

[mcat_premed3832]

The circulatory, respiratory and digestive systems depend on stretch receptors from one end to the other (except in part the venous system). The endocrine system has many, many hormones - 99% of which are unrelated to stretch receptors. There is only one clear best answer.

[bribercar2809]

I beg to disagree, because, their are many other examples, in endocrine,

In your statement you say

The following are other physiological systems which depend on stretch receptors EXCEPT:

And they all do, even endocrine, so your question is incorrect

[mcat_premed3832]

When I did the real MCAT, I had a question that forced me to choose that Cl- did not affect the membrane potential. I knew it did from my physio course but I also new it's effect was minor compared to the other answer choices and that the MCAT was based on 1st year/intro level science. Choosing the best answer was how I got my 38.

If you believe that every real AAMC question will have an unambiguous answer, then I only hope that will be true for your exam.

Statistically, Question 42 was not ranked as "Difficult".