1. PEER SUPPORT Fluid and electrolyte imbalance-Virginia Lam

2. Case study John, 23 years old male, was hit by a car and noted to have profuse bleeding. What is the first reaction of the body to compensate?

3. Kidney ◦ Autoregulation: dilation of AA and constrict the EA ◦ fast action when compensation fails ◦ Macula densa cell in juxtaglomerular apparatus in distal tubule detect an increase in sodium concentration ◦ Release adenosine and cause constriction of AA ◦ Reduce GFR ◦ Slower action ◦ RAAS Heart ◦ Sympathetic nervous response-increase cardiac output ◦ Complicated as always in medicine….also constrict AA Brain ◦ Secrete ADH EVERYWHERE ◦ Shift of fluid from ICF to ECF

4. Kidney ◦ fast action ◦ Reduce GFR ◦ -> decrease urine output ◦ Slower action ◦ RAAS -> thirst Heart ◦ Sympathetic nervous response-increase cardiac output ◦ -> tachycardia/ bounding pulse/ hypotension/ decrease cap refill Brain ◦ Secrete ADH ◦ -> decrease urine output and thirst EVERYWHERE ◦ Shift of fluid from ICF to ECF ◦ -> dry mucosa ◦ electrolyte imbalance ◦ Weight loss

5. What structures in the kidney determine the concentration of urine? (2) ◦ Loop of Hentle ◦ Countercurrent system of vasa recta ◦ What hormone is primarily involved in urine concentration? (1) ◦ Antidiuretic hormone

6. Loop of Henle The purpose of the movement of water and ion is to establish highest concentration at the bottom of LOH and lower at the top By changing the amount of ion that is reabsorbed during the active transport in ascending loop, concentration can be changed, and thus affect amount of water resorbed

7. Vasa recta Descending vasa recta: blood coming down into the medulla from the cortex comes into contact with the concentrated medullary interstitial fluid. Ions diffuse from interstitium to blood, increasing the plasma concentration Ascedning vasa recta: concentrated blood flowing up towards the cortex loses salt to more dilute medullary interstitial fluid At the result: water is diffused from LOH to vasa recta continuously

8. LOH and vasa recta = perfect couple But still, they need ADH to make them work better

9. Back to John, he is bleeding! In his case, what are the trigger to release ADH? (4 of them) 1)Decreasing blood volume detected in RA 2)Decreasing blood pressure detected by baroreceptor in aortic arch and carotid sinus 3)Increasing osmolality 4)Release of angiotensin II

10. What are the mechanism of ADH release? (5) Mechanism: 1.Omsoreceptor in hypothalamus detect increased serum osmolality 2.Increased serum osmolality will causes release of antidiuretic hormone from the posterior pituitary gland 3.ADH will bind to the receptor in the distal convoluted tubues allowing increased water reabsorption from the urine 4.the aquaporin 2 channel will move from cytoplasm to the apical membrane of the tubules, which increase the water absorption back to the blood stream 5.increased water absorption will lower the serum osmolality and thus negative feedback to the hypothalamus to reduce ADH secretion