Chemoreceptor and Baroreceptor: Facts and Resources

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What is a Chemoreceptor?

The survival of any organism is dependent on the detection of inputs from the environment. Internal chemical events result when these inputs are detected. A chemoreceptor, or chemosensor, is a sensory receptor that translates a chemical signal into an action potential.

Chemoreception is the three-stage process by which chemoreceptors function. The levels of chemoreception are detection, amplification and signaling. Chemoreceptors only bind to a certain kind of molecule. In detection, binding occurs on the cell’s surface between a molecule and a chemoreceptor protein. This action modifies the shape of the chemoreceptor. In amplification, energy from the cell changes the chemoreceptor into biochemical or electrical signals inside the cell. Amplification is often assisted by the formation of cyclic adenosine monophosphate which allows the cell to become more permeable to sodium ions and changes the electrical potential of the cell membrane. Finally, in signaling, the amplified signal is translated into a behavioral or physiological response via the nervous system.

Chemoreceptors are classified into two categories of direct and distance. One example of distance chemoreceptors are olfactory receptor neurons in the olfactory system that translate particular molecules of a substance into a familiar smell. Another example is certain neurons in the vomeronasal organ that detect pheromones which are chemicals that prompt a behavioral response in those belonging to the same species.

Illustrations of direct chemoreceptors include taste buds in the gustatory system that translate molecules in food into the detected flavors of sweet, salty, sour and bitter. There are also chemoreceptors known as carotoid bodies and aortic bodies, associated with breathing and heart rate. These can sense modifications in oxygen and perceive when carbon dioxide partial pressure increases, and when arterial pH declines. Also noteworthy is the chemoreceptor trigger zone in the brain’s medulla. This is an area that gathers inputs from drugs or hormones in the blood and communicates with the area postrema that controls the vomiting reflex.

What is a Baroreceptor?

Baroreceptors, or barosensors, are located in the blood vessels in the human body. They act as part of the baroreflex, a negative feedback system. They detect and respond to the pressure of blood flowing through them and communicate with the central nervous system to augment or lower total peripheral resistance and cardiac output. A sudden change in blood pressure provides the impetus for baroreceptors to serve as a short-term regulation mechanism for blood pressure. Their goal is to assist the mean arterial blood pressure in returning the pressure to a normal measurement. Baroreceptors sense the amount of stretch in the blood vessel walls and respond by communicating with the nervous system in response to this stretch. What follows is a modification in firing speed of the action potentials coming from the baroreceptors. The nucleus tractus solitarius in the medulla oblongata then senses changes, subsequently causing the necessary responses in the autonomic nervous system through cardiac output and systemic vascular resistance.

There are baroreceptors located in the walls of the bifurcation area of the neck in the carotid sinuses of the left and right internal carotid arteries. They are also present in the arch of the aorta in the thorax. These are all stimulated by the stretch of the arterial wall. When the pressure of the arteries increases too much, the baroreceptors incite many nerve impulses to the medulla. These impulses then block the vasomotor center through the sympathetic nervous system to the heart and blood vessels.

This rapid process causes the heart to pump more slowly. It also results in dilation of the peripheral blood vessels, which enables more blood to flow through them. These two phenomena encourage the arterial pressure back toward a normal level.

When arterial pressure dips below normal, the stretch receptors relax, activating the vasomotor center more than usual. This results in vasoconstriction and higher heart activity that returns arterial pressure back to normal.

Resources about Chemoreceptors and Baroreceptors

Information about The nematode chemoreceptor superfamily

The Impact of Cardiopulmonary Baroreceptors on Pain Perception in Individuals at Differing Risk for Hypertension by Matson, Erin L. Hockman

More definitions of Baroreceptors

More definitions of Chemoreceptor

Resource by Paige

Paige is a Licensed Esthetician at Thrive Skin Institute. She obtained a Bachelor of Science from Penn State. She earned her Esthetician degree from The California Academy

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