NBME 23 Heart rate (NBME Answers)

NBME 23 Answers

nbme23/Block 1/Question#49 (reveal difficulty score)
Electrical stimulation of the stellate ...
Heart rate 🔍 / 📺 / 🌳 / 📖
tags: autonomic

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submitted by ∗seagull(1933)

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So, T1/2-T5/6 are the sympathetic level for the heart. The stellate ganglion are cervical sympathetic ganglion. This question seems more incorrect (or a huge leap) to me. But hey, I know people will disagree.

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dentist you're right! heart rate is the only option under sympathetic control. +

drzed The cervical ganglion is a fusion of the last few cervical levels and the first thoracic level, so it is plausible. +

+6 upvote downvote
submitted by ∗kentuckyfan(47)

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Notice that A) Bronchoconstriction, B) Glandular secretion, D) Peristalsis, E) Vasodilation of skin are all under parasympathetic control.

The only sympathetic control is heart rate, which would increase.

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drzed Vasodilation of the skin is under sympathetic control as well -- beta-2 receptors when stimulated cause vasodilation (via increase of cAMP in vascular smooth muscle). The key is recognizing that stimulation of a GANGLION of the pns will lead to release of NOREPINEPHRINE, which preferentially stimulates alpha-1 receptors. Those receptors will cause vasoconstriction. If the question asked what happens when you stimulate the adrenal medulla, the answer would be (potentially) vasodilation. This is because the adrenal medulla releases EPINEPHRINE which preferentially stimulates beta-1/2 receptors. +12

jesusisking @drzed Awesome explanation except I think sympathetic response induces vasoconstriction in the skin though vasodilation in the muscles! +1

usmile1 @jesusisking yes you are correct! α1: vasoconstriction in skin and intestine ; β2: vasodilation in skeletal muscle (transmitter: only epinephrine!) +

an1 sympathetic response is going to fight or flight. you'll be sweating, you want the sweat to dissipate so your body temperature doesn't shoot up. To reduce temperature, there is vasoDILATION at the skin and vasoCONSTRICTION of the splanchnic vessels. Confirm with UW QID 19088 (image) +1

an1 ignore me^^ +

an1 actually no don't lol, check out the image it'll make sense. @drzed is correct, HR was a better option here though +

an1 re-read the question here. might be taking a big leap but maybe the electrical stimulation is a give away. Yeah stellate is SNS leading to HR increase, sweating, increased blood pressure but if it's electrical stimulation, why would the skin vasodilator? it vasodilator to get rid of excess heat, which shouldn't be present with a minor electrical stimulation +

Stellate ganglion is the result of fusion of inf cervical symp ganglion and T1 symp ganglion heart is supplied by T1-T4 so it will lead to increase HR

+4/- mhmdreyad(4)

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submitted by real_rawgary(2)

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The way I excluded vasodilation was this: the sympathetic receptor that dilates is β2, which is not stimulated by norepinephrine. So to stimulate the receptor, the stellate ganglion would have had to first stimulate the adrenal medulla to release epinephrine (stellate too high to stimulate the medulla).

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krewfoo99 But isint beta 1 (heart rate) also stimulated by Epinephrine? +

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submitted by realmedicmd(2)

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I incorrectly chose vasodilation. Found out that it’s actually vasoconstriction (vasodilation is parasympathetic):

Autonomic nerve fibers are also crucially involved in the regulation of vascular effects in the skin. Sympathetic nerve fibers release norepinephrine and/or NPY to innervate arterioles, arteriovenous anastomoses, and venous sinusoids which results in vasoconstriction, whereas parasympathetic nerves mediate vasodilatation through activation of venous sinusoides by the release of ACh and VIP/peptide histidine methionine.

https://physiology.org/doi/full/10.1152/physrev.00026.2005

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submitted by ∗consistentwrongdoer3(21)

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I thought that the primary sympathetic innervation to the heart was through T1-T4. Why would stimulation of this ganglion not affect skin vessels in the upper limb?

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methylased Stellate ganglion --> sympathetics for sweat to skin in UE + head. Apparently also to increase HR (some cardiologists ablate stellate ganglion for tachy that cant be controlled by beta blockers). +

tea-cats-biscuits The stellate ganglion is a sympathetic ganglion, so it wouldn’t increase vasodilation in the skin of the upper extremity. Also in most people, the inferior cervical ganglion is fused with the first thoracic ganglion (T1), forming the stellate ganglion. +39

sympathetikey Got this wrong too. I think upper extremity skin vasodilation (which I picked) is probably more due to local metabolites. +

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submitted by ∗criovoly(17)

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the stellate ganglion is part of the sympathetic nervous system flight or fight. Increase heart rate is the most obvious.

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