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 carotid reflex clarification  

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hello guys..i just wanna make sure if i have this concept if u can plz let me know i will really appreciate it.

carotid reflex is strech reflex controlled by CN IX....send impulse to medulla..(if anyone knows where in medulla..can u plz let me know?) messaging carotid will stimulate reflex..and increase afferent body detects it as increase in BP and HR. medulla signla CN X...increase in PANS...and decrease the HR. also cause vasodilation so..decrease in BP?

i am confused as to whether increase afferent impulse is signal to decrease to hr or increase it..when does medulla stimulate SANS response?

also last thing..if anyone can..could u plz let me know lab in HTN..w/o medication..i mean renin, angion I and II, aldosteone.

thank you very much. good luck guys.


Carotid Body Massage pathway ( can be considered as Inhibitory pathway due to excessive stimulation)
Carotid body --> via nerve IX --> Medualla ( Vasomotor Area) --> Nucleus tractus solitarius --> Dorsal motor vagal nucleus & Nucleus Ambiguus ---> Vagus nerve --> Heart resulting in bradycardia and fall in BP

Carotid Body Stimulation Pathway
Carotid body --> via nerve IX --> Medualla ( Vasomotor Area) --> Nucleus tractus solitarius --> Caudal ventrolateral Medualla --> Rostral Ventrolateral Medualla --> Bulbospinal pathway --> Intermediolateral gray column (spine thoracic cord) --> Heart, vessels, organs.

One Should remember that function of the Carotid bodies is to maintain or act according to the dissolved O2 passing through them. i.e they measure the dissolved O2 in the blood therefore the in anemia and CO poisoning the Carotid receptors are not stimulated as the Dissovled O2 is unaffected in these conditions while the Overall O2 content is markedly decreased.
Thus any stasis in blood or fall in the dissolved O2 will have sympathetic effects and if there is increase in the O2 content vagal or PANS effects will be observed.

The Baroreceptors follow the same prinicple pathway but they use Vagus as their initial pathway to Medulla.


The Baroreceptors react with a sympathetic drive or decrease their discharge in situations of low blood pressure. Their low discharges triggers the Vasoconstrictor nerves to continue their tonic discharge. When the barorecptors are stretched they increase their discharge which leads to inhibition of the vasocontrictor nerve discharges and stimulates the vagal nerve discharge leading to bradycardia and vasodilation and venodilation.


tnx a n def. helps.


well now don't confuse carotid bodies and carotid sinus, you will find the chemoreceptors on the carotid bodies and the baroreceptors in the carotid sinus. so any baroreceptor or chemoreceptor in the carotids will be innervated by the IX, those in the aortic arch will be innervated by the X.

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