Baroreceptors that regulate blood volume and control blood pressure are called low pressure or volume baroreceptors. A larger baroreceptor than this. They control the blood pressure of the systemic veins, pulmonary veins, right atrium and right ventricle. A decrease in blood volume or volume results in a decrease in blood pressure. This message reaches the hypothalamus. It then comes from the hypothalamus to the pituitary gland. Antidiuretic or vasopressin hormone is released from the pituitary gland. Antidiuretic hormone (ADH) increases renal water absorption. The kidneys reabsorb water from the urine and mix it with the blood. As a result, blood volume increases and blood pressure increases.
Vasopressin hormone directly causes vasoconstriction and increases blood pressure. The renin hormone is produced by the cells of the juxta-glomerulus. It increases blood volume and blood pressure.