Fainting: The Link Between the Heart and Brain


For some, fainting can be a daily struggle, an anticipation of the next bout of lost

consciousness. Scientists have begun to recognize that there appears to be a

connection between the brain and heart that leads to fainting spells and there seems to

be an added genetic component for theformation of the heart. The Bezold-Jarisch reflex

(BJR) is when cardiac inhibitor receptors are activated leading to dilations of blood

vessels, hypotension, a slow heart rate, and eventually syncope or fainting. This reflex

was found to occur due to activation of the specific type of vagal sensory neurons called

NPY2R.


Lovelace et al. did a study on mice, where they discovered a connection between

vagal neurons, vNAS stalled heartbeats, and BJR. In order to discover this connection

they manipulated the specific neurons, NPY2R. By manipulating these neurons, the

mice went from their normal activities to immediately fainting. However, when these

neurons were removed, the mice stopped fainting all together. To excite the neurons, a

method called optogenetics was used. Optogenetics is when light stimulates certain

channels and pumps the target neurons, which consequently activates the neurons.

This testing also revealed that there appears to be restricted blood flow to the brain

during these activations, which furthers the likelihood of fainting. Restricted blood flow is

due to a decreased cardiac output and increases in the volume of blood in the left

ventricle. In the discussion, they come to the conclusion that BJR is activated by

NPY2R VSNs that act as substrates for BJR. This conclusion basically states that

NPY2R VSNs causes BJR to occur, which then leads to syncope.

With a better understanding of the neural-heart connection that leads to syncope,

the next steps are to determine if it is plausible to remove NPY2R neurons in the human

brain, without causing damage. The cardiac inhibitor receptors for BJR are activated by

NPY2R VSNs, it’s substrate. If the substrate were to be removed, then the cardiac

inhibitor receptors don’t activate cardiac inhibition. This discovery is important because

it gives hope to those who might be scared to go out their own door due to unexpected

fainting.


Posted by: Alexis Carson (9)

Lovelace JW, Ma J, Yadav S, Chhabria K, Shen H, Pang Z, Qi T, Sehgal R, Zhang Y,

Bali T, et al. 2023 Nov 1. Vagal sensory neurons mediate the Bezold–Jarisch reflex and

induce syncope. Nature.:1–10. doi:https://doi.org/10.1038/s41586-023-06680-7.

[accessed 2023 Nov 5]. https://www.nature.com/articles/s41586-023-06680-7#Sec9.

Comments

  1. AnonymousNovember 27, 2023 at 12:53 PM

    Hi Alexis this study was really interesting to learn about. This seems like am important medical break through for those that suffer with fainting disorders. Fainting can be really dangerous and lead to people having to completely alter their daily life. Being able to m=remove neurons that cause fainting seems like an ideal cure. It would be interesting to learn more about what the long term effects could be for the future.
    -Payton Carroll

    ReplyDelete
  2. Madeline GouldNovember 28, 2023 at 10:21 AM

    Hi Alexis! This is very interesting. I have always been very intrigued by fainting because it seems like such a sudden thing that happens and I never knew how it occurred. It makes sense that there is restricted blood flow to the brain during this but I had never known that. It seems very groundbreaking that it has been discovered that there is a neuron that can be removed to prevent this, but I understand why it is still unknown if it is safe to remove from the human brain. If it is a safe procedure, I think this could be very helpful!

    ReplyDelete
  3. AnonymousNovember 28, 2023 at 5:10 PM

    Hello Alexis! This is a really interesting post. I have a fear of shots and needles, and I often faint when I have to get certain procedures done. It is definitely a scary feeling, and can be really uncomfortable. I am glad to hear that there may be some hope in controlling unexpected fainting. While I know this was only animal testing, it still helps us get some insight into the physiology behind fainting.

    -Anya Quaglietta

    ReplyDelete
  4. Molly McGonagleNovember 29, 2023 at 7:22 AM

    Hi Alexis,
    This post really caught my attention because my roommate has a history of fainting. We always wondered what caused it because there was no common issue with each time it happened. This was interesting to learn about with the connection to the heart.

    ReplyDelete
  5. AnonymousNovember 29, 2023 at 9:26 AM

    Hi Alexis,
    This is a super interesting post! I think it's really interesting how different people can be when it comes to fainting because I personally have never actually fainted before, but then there are people who have a chronic condition. With genetics playing a role in it, this would make a lot of sense. The study done with mice was super interesting too- how removing neurons themselves can prevent fainting all together. Hopefully we can use this to better understand and prevent unexpected fainting.

    -Sophia Rinaldi

    ReplyDelete
  6. AnonymousDecember 4, 2023 at 10:36 AM

    Hi Alexis, this was well said information. I always had an idea of fainting but this is put together, its so fascinating how the connection between the brain and heart can cause this. I have participated with study including mice so I'm super interested in how Lovelace did this study.
    -Aaliyah Thompson.

    ReplyDelete

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