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Baroreceptor Reflex:

In response to acute changes in blood pressure, the body responds through the baroreceptors located within
blood vessels.

Baroreceptors are a form of mechanoreceptor that become activated by the stretching of the vessel.

This sensory information is conveyed to the central nervous system and used to influence peripheral vascular
resistance and cardiac output.

There are two forms of baroreceptors.

1. High-Pressure Baroreceptors

Two baroreceptors are located within the high-pressure arterial system.

• The carotid baroreceptor responds to both increases and decreases in blood pressure and
sends afferent signals via the glossopharyngeal nerve (CN IX).
• The aortic arch baroreceptor responds only to increases in blood pressure, sending its
signals through the vagus nerve (CN X).

These both send signals in response to the physical distortion of the vessel.

The stretch of the vessel leads to an increase in action potential relayed from the sensory endings located in the
tunica adventitia of the artery.

These action potentials get transmitted to the solitary nucleus that signals to autonomic neurons secrete
hormones to affect the cardiovascular system. Activation of the aortic baroreceptor during increases in blood
pressure effectively inhibits the efferent sympathetic nerve response.

[5] On the other hand, if an individual’s blood pressure were to fall such as in hypovolemic shock, the rate of
action potential from the baroreceptors would be decreased due to reduced depolarization; this would lead to
reduced inhibition of sympathetic activity, resulting in a reflex to increase pressure.

2. Low-Pressure Baroreceptors

These baroreceptors are present within the low-pressure venous system. They exist within large veins,
pulmonary vessels, and within the walls of the right atrium and ventricle.

The venous system has compliance approximately 30 times greater than that of the arterial system [6].

Changes in volume largely influence the baroreceptors in the venous system. Decreased frequency in action
potentials in low-pressure scenarios leads to the secretion of antidiuretic hormone, renin, and aldosterone.

These lead to a downstream effect to regulate arterial pressure.

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