USMLE and COMLEX Prep: Cranial Nerve Nuclei

BR 47: USMLE and COMLEX Prep: Cranial Nerve Nuclei

Session 47

Using our knowledge of cranial nuclei and some spatial awareness, which cranial nerve nuclei receives fibers from the carotid baroreceptors? Let’s find out!

Once again, I’m joined by Dr. Mike Natter from BoardVitals. If you are looking for some more help with your board prep, check out everything they have to offer.

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[02:44] Question of the Week

Which of the following cranial nerve receives fibers from the carotid baroreceptors?

(A) nucleus ambiguus

(B) superior salivary nucleus

(C) inferior salivary nucleus

(D) nucleus tractus solitarius, the caudal portion

(E) nucleus tractus solitarius, the rostral portion

[05:44] Thought Process Behind the Right Answer

Caudal is the tail part and the rostral is the front part. This comes back to being granular and doing rote memorization of your nuclei responsible for certain things.  In this case, the carotid baroreceptors.

“When you can't logic your way through it, then using your test taking strategies is always helpful.”Click To Tweet

And so this case happens to be the nucleus tractus solitarius of the caudal portion. It receives our visceral sensory fibers through the glossopharyngeal nerve from the carotid sinus baroreceptors. That’s what you would massage in times of SVT. And what is SVT? Supra ventricular tachycardia. Supra means above. So it’s not coming from the ventricles. It’s above the ventricles and your tachycardia. So you’re, you’re tacking at above a hundred beats per minute. The first thing you would want to do when you see your patient is just tap them in a way and they’re not hypotensive. Give him a little massage on the neck there.

The pressure at which you’re supposed to push is the same pressure you would push to indent that of a tennis ball. That seems like a lot of pressure. Then you can go towards your vagal maneuvers and you have them bare down and be willing to straw on stuff. Once that k goes south, you really have to grab some adenosine and see what else you got. But if someone is hypotensive, that’s when things need to be done a little bit more urgently.

[08:59] Understanding the Other Answer Choices

The nucleus ambiguus is something we identified last episode as the GPA or higher than a B.  Remember that as our branchial motor fibers that go to the pharynx and the larynx. That goes through our nucleus ambiguus and it’s a branch of our glossopharyngeal.

B is the super solitary nucleus and the innervates the lacrimal, sublingual, and submandibular as well as nasal and palatine glands.

C is our visceral motor fibers from the inferior salivary nucleus that innervate the parotid.

And E is the irrational portion of the cranium nerve nucleus that receives the visceral sensory fibers through the chorda tympani. That’s the taste for the anterior two thirds of the tongue, which is a special branch of the facial.

[10:10] Final Thoughts

These questions are not straightforward. They are second and third removed type questions where you have to know a lot of information to answer one question properly. The more that you practice, the more that you listen to this podcast. Hopefully the more of this information will get stuck in your brain somewhere. That’s the ultimate goal.

Don’t forget to go check out BoardVitals and check out everything that they have to offer. Use the promo code BOARDROUNDS to save 15% off.

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