Both large brain vessels and choroidal vasculature have sympathetic inervation which provides regulation of blood flow. In the brain this prevents overperfusion in acute hypertension. In the choroidal vasculature it prevents that changes in the systemic blood pressure affect choroidal blood pressure. This symphatetic activity is modulated by a baroreflex. I would like to know where are these barorreceptor cells located. Are they located in the carotid sinus or in the large brain and choroidal vessels?. I also would like to know if these barorreceptor signals have a representation in counsciousness in the same way carotid sinus´s barorreptors do (you can feel the distension of the carotid sinus). It´s a important question because if they are counsciously detectable it may be posible to voluntary modulate that symphatetic activity by mentally evoking this sensation, in the same way that evoking local thermal sensations (feeling heat or cold without real stimuli) can produce local vasomotor effects (This has been proven during hyponosis and waking-imagination experiments). I appreciate your answers. Thank you.
Hi Juan,
i would say that for the brain vessels' regulation a myogenic mechanism (Bayliss effect) is most important. This effect should be independent from the vegetative control of vessels due to baroreflex. Besides, metabolic control affects the brain vessels' regulation.
However, obviously the overall regulation is complex and there is much interaction between different mechanisms. Therefore, to some (minor) extend, even sympathetic regulation due to the baroreceptors might contribute. In this case i would expect the "normal" arterial baroreceptors (the most important ones are located in the carotid sinus and even in the aortic arch) to sense the blood pressure.
Greetings, Sebastian
Hi,
You have mentioned " you can feel the distension of the carotid sinus " would you please provide the evidence behind this?
Thanks for your answers.
Hi Sebastian, I was talking about acute hypertension, in which, as far as I know, symphatetic activation plays an important role in preventing damaging overperfusion. There a interesting study in animals with bilateral symphatetic denervation exposed to acute hypertension.
Hi Ali. I´m sorry. I think I misinterpreted the feeling of distension (which may be related to the distension of surrounding body tissues)as a afferent signal from baroreceptors with cortical representation. However, I am not completely sure that you cannot directly feel baroreceptor distensión, because i´ve red that it has interoceptive awareness representation in the insular cortex.
Now I am in my last year on medicine degree and I have to focus on my final exams until 16th March, so I will leave until then. I´m sorry for my answers being to short, I will be back when I finish my exam. I´m also sorry for my bad english. I am spanish and I need to write slowly to achieve a proper gramar and now I am in a hurry.
Hi Juan, with regards to cardiac perception, a common task is the heartbeat counting task in which subjects are asked to count the heartbeats that they feel. People can feel their heartbeats in different regions in the body but mostly in chest. The neurological pathway(s) of cardiac perception is not well understood, and not well studied. It is assumed that baroreceptors are involved in cardiac perception but there is no direct evidence. The most direct evidence comes from study by Khalsa Article The Pathways of Interoceptive Awareness
comparing patients with brain lesions in insula and healthy controls after applying lidocaine to the skin in regions with maximal heartbeat sensation. This study shows that both somatosensory afferents from skin and a network that includes insula (and perhaps baroreceptors) are involved in cardiac perception.Assuming that baroreceptors are involved in cardiac perception we examined the association between baroreceptor sensitivity and interoceptive accuracy using the heartbeat counting task and found an independent association which support the role of barorecptors in cardiac perception, but this can be yet indirect (by modulating attention etc.) and not distinguishing carotid from aortic baroreceptors
https://ppw.kuleuven.be/ogp/anderepdf/ali-gholamrezaei-spr-2017-poster.pdf
Anyway, to my knowledge, there is no direct evidence that individuals can "feel" the distension of the carotid sinus, if by "feel" you mean being aware of it.
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