Page 14 - G43 ASSIGNMENT

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

Baroreceptors are groups of nerve endings that are able to sense the swelling associated with changes in blood
pressure. In other words, these are baroreceptors. They are abundant in the carotid sinus and in the aortic arch.

Baroreceptors are responsible for providing useful information to the brain regarding blood volume and blood
pressure. When the blood volume increases, the vessels dilate and activity begins at the baroreceptors. The
reverse process occurs when blood levels drop.

When an aneurysm occurs due to increased pressure, the activity of the vagus nerve increases. This causes
inhibition of the sympathetic outflow of the RVLM (ventral rostral bulb). rostral ventral medulla), which
eventually leads to decreased heart rate and blood pressure.

In turn, a decrease in blood pressure leads to a decrease in baroreceptor output signal, which leads to inhibition
of central sympathetic control sites and a decrease in parasympathetic activity.

The end effect is an increase in blood pressure.

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].

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