Low pressure receptors

Low pressure baroreceptors are baroreceptors located in large systemic veins and in the walls of the atria of the heart. They are also called volume receptors and cardiopulmonary baroreceptors.
Structure.
Low pressure baroreceptors are located in large systemic veins and the atria of the heart. In the right atrium, the stretch receptors occur at the junction of the venae cavae. In the left atrium, the junction is at the pulmonary veins.
Function.
Low pressure baroreceptors respond to changes in the wall tension, which is proportional to the filling state of the low pressure side of circulation (below 60 mmHg). Thus, low pressure baroreceptors are involved with the regulation of blood volume. The blood volume determines the mean systemic pressure throughout the system, in particular in the venous side where most of the blood is held. Increasing stretch of the receptors stimulates both an increase in heart rate and a decrease in vasopressin (ADH) secretion from posterior pituitary, and renin and aldosterone. The decrease in vasopressin secretion results in an increase in the volume of urine excreted, serving to lower blood pressure.
In addition, stretching of atrial receptors increases secretion of atrial natriuretic peptide (ANP), which promotes increased water and sodium excretion through the urine.