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NBME 22 Answers

nbme22/Block 1/Question#35

A 35-year-old man is brought to the hospital after ...

Alteration of the thermostatic set point

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submitted by keycompany(142),

Alteration of the thermostatic set point is a hypothalamic process mediated by prostaglandins and is independent of the sympathetic nervous system.

B, C, D, and E all require sympathetic nerves to ellicit a response.

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submitted by qfever(5),

Hypothalamus controlling temperature set point is briefly mentioned in Pathoma 2018 edition page 13, Chapter 2 III Cardinal signs of inflammation D. Fever

Pyogenes -> macrophage release IL-1 and TNF -> increased cyclooxygenase activity in hypothalamus perivascular cells -> increased hypothalamus PGE2 -> raised temperature set point

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submitted by gribear(0),

Can someone explain why when you transect the spinal cord superior to the level of sympathetic outflow -- and you get a systemic infection -- the response is alteration of the thermostatic set point?

its_raining_jimbos  So I chose that one because set point is controlled by the hypothalamus (PGE2 and IL-1 mediate fever in the hypothalamus) and the rest of the answer choices involved something below the level that has been transected. Not 100% sure if that’s accurate though. +1  
noselex  Agreed with @its_raining_jimbos -- Fever is mediated by altering set point in hypothalamus. All the other choices, as far as I can tell, involve sympathetic nerves and their effects at target organs. +  

 -1  upvote downvote
submitted by gh889(38),

From ShoryukenHadooken on reddit:

What the question is getting at is the sympathetic chain was spared. It was a terrible way of wording it.

Your anterior hypothalamus is responsible for cooling features and is under parasympathetic control. A lesion would cause hyperthermia.

Your posterior hypothalamus is responsible for heating when you're cold and to generate the Fever response and is under sympathetic control. A lesion would cause hypothermia.

In this question it is simply asking a person gets sick, hypothalamus was spared, what happens.

Answer: hypothalamus will still be able to elevate set body temperature to battle infection.

Hint: IF they give a question similar to this but reworded to include a lesion of the sympathetic fibers or of the hypothalamus, you would in turn NOT be able to generate a fever response to infection. The hypothalamus would be entirely under parasympathetic control

This adds more context to the fact the Q states that the sympathetics was spared

oslerweberrendu  So, this says sympathetic also spared and hypothalamus also spared. Then what was wrong with this clinical case?? +  
adong  i think the sympathetic system is actually impaired b/c it's cut before it can "outflow"...at least it's the only way this makes sense +  
suckitnbme  I agree. I think the question stem is saying the sympathetics were lesioned. Not that they were spared. +