Low pressure baroreceptors or low pressure receptors are

baroreceptor Baroreceptors (or archaically, pressoreceptors) are stretch receptors that sense blood pressure. Thus, increases in the pressure of blood vessel triggers increased action potential generation rates and provides information to the central nervous s ...

s that relay information derived from blood pressure within the

autonomic nervous system The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates viscera, internal organs, smooth muscle and glands. The autonomic nervo ...

. They are stimulated by stretching of the vessel wall. They are located in large systemic veins and in the walls of the

atria Atria may refer to: Science *Atrium (heart) (plural: atria), an anatomical structure of the heart *Atria (genus), a flatworm genus in the family Dendrocoelidae * Atria (star) or Alpha Trianguli Australis, a star in the constellation Triangulum Aus ...

of the heart, and pulmonary vasculature. Low pressure baroreceptors are also referred to as volume receptors, cardiopulmonary baroreceptors,Armstrong, Maggie, et al. ''Physiology, Baroreceptors - Statpearls - NCBI Bookshelf''. 9 Mar. 2022, https://www.ncbi.nlm.nih.gov/books/NBK538172/ . and veno-atrial stretch receptors

Structure

There are two types of cardiopulmonary baroreceptors, both of which are found within the

atrial The atrium (; : atria) is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves. ...

endocardium The endocardium (: endocardia) is the innermost layer of tissue that lines the chambers of the heart. Its cells are embryologically and biologically similar to the endothelial cells that line blood vessels. The endocardium also provides prot ...

. Type A receptors are activated by wall tension, which occurs via atrial contraction during ventricular diastole. Type B receptors are activated by wall stretch, which occurs via atrial filling during ventricular systole. In the

right atrium The atrium (; : atria) is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves. ...

, the stretch receptors occur at the junction of the

venae cavae In anatomy, the ''venae cavae'' (; ''vena cava'' ; ) are two large veins (great vessels) that return deoxygenated blood from the body into the heart. In humans they are the superior vena cava and the inferior vena cava, and both empty into the ...

. In the

left atrium The atrium (; : atria) is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves. ...

, the junction is at the

pulmonary veins The pulmonary veins are the veins that transfer oxygenated blood from the lungs to the heart. The largest pulmonary veins are the four ''main pulmonary veins'', two from each lung that drain into the left atrium of the heart. The pulmonary ve ...

Function

Low pressure baroreceptors are primarily involved in the regulation of the blood volume. Low pressure baroreceptors have both circulatory and renal effects, which produce changes in hormone secretion. Stimulation of these receptors causes the atria to release

atrial natriuretic peptide Atrial natriuretic peptide (ANP) or atrial natriuretic factor (ANF) is a natriuretic peptide hormone secreted from the cardiac atria that in humans is encoded by the ''NPPA'' gene. Natriuretic peptides (ANP, BNP, and CNP) are a family of ho ...

. This hormone acts on the kidneys to increase sodium excretion, which increases urine production and thereby leads to a decrease in blood pressure. Through the vagal nerve, impulses transmits from the atria to the vagal center of the medulla. This causes a reduction in the sympathetic outflow the kidney, which results in decreased renal blood flow and decreased urine output. This same sympathetic outflow is increased to the

sinoatrial node The sinoatrial node (also known as the sinuatrial node, SA node, sinus node or Keith–Flack node) is an ellipse, oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of Cell (biology), cells known as pa ...

in the atria, which causes increased heart rate/cardiac output. These cardiopulmonary receptors also inhibits vagal stimulation in the vasoconstrictor center of the medulla resulting in decreased release of

angiotensin Angiotensin is a peptide hormone that causes vasoconstriction and an increase in blood pressure. It is part of the renin–angiotensin system, which regulates blood pressure. Angiotensin also stimulates the release of aldosterone from the adr ...

aldosterone Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays ...

, and

vasopressin Mammalian vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the ''AVP'' gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It ...

. These receptors also cause a renal vasodilation, resulting in increased diuresis. This decreases the blood volume, resulting in the decrease of blood pressure.^{disputed – discuss''">Talk:Atrial volume receptors">discuss''/sup>

See also

* Renin–angiotensin system

The renin–angiotensin system (RAS), or renin–angiotensin–aldosterone system (RAAS), is a hormone system that regulates blood pressure, fluid, and electrolyte balance, and systemic vascular resistance.

When renal blood flow is reduced, ...

* Bainbridge reflex
* High pressure receptors
* Atrial volume receptors

References

{{DEFAULTSORT:Low Pressure Receptor Zones
Sensory receptors}