Difference Between Baroreceptors and Chemoreceptors

The key difference between baroreceptors and chemoreceptors is that baroreceptors are mechanoreceptors responding to blood pressure changes while chemoreceptors are cells sensing the concentration of chemicals in the surrounding extracellular fluid.

Baroreceptors and chemoreceptors are two types of sensory cells. Baroreceptors are mechanoreceptors that respond to increase or decrease in blood pressure or arterial stretch. In simple words, they sense the mean arterial pressure. In contrast, chemoreceptors respond to levels of oxygen, carbon dioxide, and pH. However, both receptors contribute to bringing about cardiovascular changes. Both baroreceptor and chemoreceptor reflexes exert considerable influence on autonomic control of the heart and blood vessels.

CONTENTS

1. Overview and Key Difference
2. What are Baroreceptors 
3. What are Chemoreceptors
4. Similarities Between Baroreceptors and Chemoreceptors
5. Side by Side Comparison – Baroreceptors vs Chemoreceptors in Tabular Form
6. Summary

What are Baroreceptors?

Baroreceptor is a mechanoreceptor that responds to changes in blood pressure. Blood pressure changes occur as a response to the change in the tension or stretch of the arterial wall.  They are found in the carotid sinus and in the aortic arch. Baroreceptor in carotid sinus responds to both increase/decrease in arterial pressure.

Baroreceptor in the aortic arch primarily responds to an increase in arterial pressure. Baroreceptor reflex is a mechanism which is a fast response to blood pressure changes. It tries to keep the arterial pressure constant. Carotid sinus reflex maintains normal blood pressure in the brain. Aortic reflex maintains general systolic blood pressure. Baroreceptor reflexes work in both directions.

What are Chemoreceptors?

Chemoreceptors are cells that respond to chemical changes in the blood, especially chemical concentrations in CO₂, O₂ and H⁺ (pH). When chemoreceptors detect a change in CO₂, O₂ and H⁺, they send impulses to the cardiovascular centre.  There are two types of chemoreceptors as peripheral chemoreceptors and central chemoreceptors. Peripheral chemoreceptors are located in carotid bodies in the carotid sinus and aortic bodies along the aortic arch. Central chemoreceptors are located in the medulla.

Chemoreceptor reflex mediates the ventilatory response to hypoxia and hypercapnia. Hypoxia is the fall in arterial PO₂ while hypercapnia is the increase in arterial PCO₂. Once chemoreceptor reflex is activated in such conditions, they help to regulate respiratory activity in order to maintain arterial blood PO₂, PCO₂, and pH within appropriate physiological ranges. Otherwise, impaired gas exchange in the lungs decreases arterial PO₂ and pH and increases arterial PCO₂.

What are the Similarities Between Baroreceptors and Chemoreceptors?

• Both baroreceptors and chemoreceptors are sensory cells.
• During exercise, both baroreceptors and chemoreceptors contribute to bringing about cardiovascular changes.
• Baroreceptor and chemoreceptor reflexes exert considerable influence on autonomic control of the heart and blood vessels, especially in stressful situations.
• Both baroreceptors and chemoreceptors are located in carotid sinus and arch of the aorta.
• They send impulses to the cardiovascular centre.

What is the Difference Between Baroreceptors and Chemoreceptors?

Baroreceptors are mechanoreceptors that respond to blood pressure changes while chemoreceptors are sensory cells that respond to chemical composition changes in the blood. Therefore, baroreceptors monitor the arterial pressure while chemoreceptors detect concentration changes of oxygen, carbon dioxide and pH in the blood. Thus, this is the key difference between baroreceptors and chemoreceptors. Besides, baroreceptors are found in the carotid sinuses and aortic arch. Chemoreceptors are found in the carotid and aortic bodies and on the ventral surface of the medulla.

Moreover, baroreceptor reflex keeps blood pressure in the normal range while chemoreceptor reflex keeps levels of oxygen, carbon dioxide and pH levels in normal ranges in the blood.

Below infographic summarizes the difference between baroreceptors and chemoreceptors.

Summary – Baroreceptors vs Chemoreceptors

The nervous system regulates blood pressure through baroreceptor and chemoreceptor reflex arcs. Baroreceptors are cells that monitor the changes in blood pressure. In contrast, chemoreceptors are cells that measure the chemical composition in blood. They respond to changes in pH, O₂ concentration and CO₂ concentrations in blood. Both types of receptors try to keep pressure and chemical composition in the blood in normal ranges. So, this summarizes the difference between baroreceptors and chemoreceptors.

Reference:

1. “CV Physiology | Arterial Baroreceptors”. Cvphysiology.Com, 2020, Available here.
2. Toledo, Camilo, et al. “Contribution of Peripheral and Central Chemoreceptors to Sympatho-Excitation in Heart Failure.” The Journal of Physiology, John Wiley and Sons Inc., 1 Jan. 2017, Available here.

Image Courtesy:

1. “Baroreceptor reflex pathway” By Alan Sved and David Nascari – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Chemoreceptor reflex response to hypoxia” By David Nascari and Alan Sved – Own work (CC BY-SA 4.0) via Commons Wikimedia