Baroreceptor Reflex

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BARORECEPTOR REFLEX

Regulates blood pressure within seconds

Life saving reflex

Also called baroreflex or sino-aortic reflex


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Receptors and stimulus Baroreceptors in carotid sinus and aortic arch are stimulated when

blood pressure rises which ultimately stimulates nucleus tractussolitarious( NTS) via 9th and 10th cranial nerve.

Baroreceptors detect change in pressure in blood vessel andchambers of heart.

It is classified into 2 categories- high pressure- located in ventricle and arterial side of circulation

low pressure- located in atria and pulmonary circulation.

Increased blood pressure causes distension of carotid sinus and

aortic arch while decreased blood pressure decreases receptorstimulation.


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Afferent pathway Hering nerve branch of 9th cranial nerve

afferent from carotid sinus

Aortic nerve branch of 10th cranial nerve

afferent from aortic arch


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Centers Centers for Baroreceptors reflex are medullary

cardiovascular center which are of two types-

1. Vasomotor center

2. Cardioinhibitory center


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Efferent Pathway andEffector OrganEfferent fibers for baroreceptors are

1. Sympathetic fibers intermediolateral gray column

originate from spinal cord

controlled by

Vasomotor center

1. Vagus nerve Nucleus tractus solitariusoriginate from


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Responses Depends on

1. Nature of change in blood pressure(increases or decreases)

2. Degree and rate of change in blood pressure.


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When blood pressure increases

Increasesd blood pressure

Strech of carotid sinus

( activation of baroreceptors )

Increased discharge in 9

th

and 10

th

cranial nerve

Stimulation of NTS

Activation of vagus nerve Inhibition of VMC

Decreased heart beat Decreased myocardial Vasodilation

contractility

Decreased cardiac

output

Decreased blood pressure


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When blood pressure decreases

Decreased blood pressure

Less strech of carotid sinus

( less activation of baroreceptors )

Decreased discharge in 9th and 10th cranial nerve

Less stimulation of NTS

Inhibition of vagus nerve Disinhibition (activation) of VMC

Increased heart rate stimulation of sypathetic

outflow

Increased myocardial vasocontriction

contractility

Inceased cardiac output

Increased blood pressure


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Types of response1. Dynamic or Phasic response

Response to change in pulse pressure

2. Static or tonic response

Response to change in sustained pressure


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Physiological Significance ofBaroreceptor Reflex1. When blood pressure falls baroreceptor reflex operates within few

seconds to correct the pressure which is life saving in hypotension and

hemorrhage.

2. Baroreceptors and their reflex pathway constitute a feedback mechanism

to stabilize blood pressure over a wide range of fluctuation in pressure.

3. Baroreceptor resetting occurs in chronic hypertension

Documents

Baroreceptor Reflex