Volume Regulation Group 7 Tiffany Liu, Melvin Aguda, Phillip Celerian, Joshua Stefaroi, Jasmine Brar, Christina Aga, Sara Condra, Sandy Huang, Liz Farrington, Emma Berg, Abby McInnis, Jim Nguyen,

What is “Volume Regulation”? The simultaneous adjustment of plasma volume AND blood pressure to maintain adequate perfusion of tissues The movement (or circulation) of plasma throughout our body requires maintenance of our blood pressure

How does this work? Volume Regulation occurs in 3 steps: Monitoring Baroreceptors Signaling Renin-angiotensin-aldosterone system (RAAS) sympathetic activation antidiuretic-hormone (ADH) Action at various targets Acts on THREE main targets to increase plasma volume and blood pressure

1st Step: Monitoring Baroreceptors specialized tissues → located throughout our body sensitive to changes in blood pressure ACTIVATED baroreceptors send signals that affect both blood pressure and plasma volume Is activated usually when volume is low We might want to use this diagram to explain that baroreceptors trigger the posterior pituitary to release ADH, starting this chain of events :)

2nd Step: RAAS (Renin-Angiotensin-Aldosterone-System)

Sympathetic Activation Sympathetic nervous system is activated when volume is low Sympathetic activation stimulates the nerves to target organs releasing sympathetic hormones such as epinephrine, norepinephrine, and dopamine

ADH (Antidiuretic Hormone) or Vasopressin -Made in the hypothalamus & stored/released from the posterior pituitary What causes its release? - Increased blood concentration (osmolarity) or decreased blood volume Mechanism of action/ effects Increased ADH Increased Aquaporins( water channels) in the collecting duct Increased water absorption via Aquaporins Small concentrated urine

3rd step: Target Organs The signals act on three main targets: Kidneys Heart Vasculature - Action at the kidney affect plasma volume - Action at the heart and vasculature affect blood pressure

Clinical Correlation - Hypervolemia: due to inadequate blood pressure Characterized primarily by peripheral edema CHF and liver disease - Hypovolemia: due to the loss of plasma volume Associated with disorders involving fluid loss such as vomiting, diarrhea, and blood loss Characterized by dry mucous membranes, tachycardia, and orthostatic vital signs - Low effective circulating volume is associated with both hypervolemia and hypovolemia

Summary - Volume regulation is the simultaneous adjustment of plasma volume AND blood pressure to maintain adequate perfusion of tissues - Plasma volume is affected by signals that influence sodium and water resorption - Blood pressure is affected by signals which influence CO and PVR - Volume regulation occurs in three steps: Monitoring Signaling Action at targets - A patient can have shifts in their volume status resulting in hypervalemia and hypovolemia which are both associated with having too low of an effective circulating volume