as a consequence of reduced blood volume the macula densa
Macula densa Macula densa cells sense changes in sodium chloride level, and will trigger an autoregulatory response to increase or decrease reabsorption of ions and water to the blood (as needed) in order to alter blood volume and return blood pressure to normal.
Inferior vena cava The inferior vena cava is a vein. It carries deoxygenated blood from the lower half of the body to the right atrium of the heart.[2]