Question

How are the kidneys involved in controlling blood volume? How is the volume of blood in the body related to arterial pressure?

Answer 1

Hint: The amount of blood is measured by the quantity of water and sodium absorbed, excreted into the urine by the kidneys, and lost via the gastrointestinal tract, lungs, and skin. The levels of consumed and missing water and sodium are highly variable. The kidneys control the amount of water and sodium lost to the urine to maintain blood flow within a reasonable range.

Complete answer:
-Adjusting the amount of water and sodium lost in the urine is the primary process by which the kidneys control blood flow.
-Sodium transport is controlled by angiotensin II at different locations along the proximal tubules, thick ascending limbs of the Henle loop, distal and accumulating tubules, which increases sodium transport, contributing to sodium retention.
-Another hormone(aldosterone) activates sodium transfer from the tubular fluid to the interstitium in the accumulating tubules.
-Angiotensin II and aldosterone together have a powerful mechanism for increasing the retention of sodium and, ultimately, the amount of fluid in the body.
-In late distal tubules and accumulating tubules, a third hormone, antidiuretic hormone (ADH), increases water permeability.
-Blood volume changes impact arterial pressure by changing cardiac output. Central venous pressure is increased by an increase in blood flow. This raises the right atrial pressure, diastolic pressure at the right ventricular end, and length.
-This increase in preloaded ventricular activity raises the amount of ventricular stroke.
-An rise in the volume of right ventricular stroke increases the influx of pulmonary venous blood to the left ventricular and thereby increases the volume of left ventricular preload and stroke.
-An rise in the volume of the stroke then raises cardiac output and blood pressure in the artery.

Note: -Renin-angiotensin-aldosterone (RAAS) system activation allows the kidneys to increase sodium retention, which leads to decreased water loss in the urine and hence blood volume expansion.