Also known as:
a. Baroreflex
b. Sinoaortic reflex
c. Pressure buffer mechanism

Components of Reflex:

Stimulus: Rise in arterial blood pressure

Baroreceptors (Pressosensors): Stretch receptors in -
a. Aortic arch
b. Carotid sinus
c. Left ventricle
d. Subclavian arteries,etc.

Afferent nerves:
a. Glossopharyngeal (CN IX) for Carotid sinus
b. Vagus (CN X) for other receptors

Medullary Centers:
Through Solitary Tractus nucleus (NTS) to-
a. Stimulation of Cardiac Inhibitory center (CIC)
b. Inhibition of vasomotor center (VMC)
c. Inhibition of respiratory center

Efferent:
VMC ---> Sympathetic
CIC ---> Parasymathetic

Response:
a) + Parasympathetic ---> Bradycardia ---> Decreased cardiac output ---> Decreased blood pressure

b) - Sympathetic:
i. Bradycardia ---> Decreased cardiac output
ii. Vasodilation ---> Decreased peripheral resistance ---> Decreased blood pressure

Stimulation of baroreceptors occurs linearly with increased blood pressure but when these are maximally stimulated, further rise in blood pressure cannot increase stimulation.

Resetting of Baroreceptor:
a. Persistent raised BP for > or = 2 days ---> receptors operate at new level ---> receptors not stimulated
b. Also observed with persistent low BP

Carotid Sinus Syndrome:
Hypersensitive baroreceptors ---> Slight pressure on neck ---> Severe inhibition of heart ---> Fall in Blood pressure
May faint on wearing a tight collar or a neck tie

Baroreceptor Reflex Animation Video

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