28: Regulation of Extracellular Fluid Osmolarity and Sodium - PowerPoint PPT Presentation

By: Dr. Foadoddini Department of Physiology & Pharmacology Birjand University of Medical Sciences 28: Regulation of Extracellular Fluid Osmolarity and Sodium Concentration

0.5 20 L 50 1200 mOsmol/L

Countercurrent Mechanism • Interaction between the flow of filtrate through the loop of Henle (countercurrent multiplier) and the flow of blood through the vasa recta blood vessels (countercurrent exchanger) The solute concentration in the loop of Henle ranges from 300 mOsm to • 1200 mOsm

Countercurrent Mechanism Produces a Hyperosmotic Renal Medullary Interstitium http://www.colorado.edu/intphys/Class/IPHY3430-200/countercurrent_ct.html http://www.cellphys.ubc.ca/undergrad_files/urine.swf http://bio-alive.com/animations/anatomy.htm

Urea Contributes to Hyperosmotic Renal Medullary Interstitium and to a Concentrated Urine Permeable to H2O if ADH 50%

Countercurrent Exchange in the Vasa Recta Preserves Hyperosmolarity of the Renal Medulla

Countercurrent Multiplier and Exchange • Medullary osmotic gradient • H 2 O → ECF → vasa recta vessels

Quantifying Renal Urine Concentration and Dilution: "Free Water" and Osmolar Clearances 2.1 * 142 = 298 mOsmol/L

29: Renal Regulation of Potassium, Calcium, Phosphate, and Magnesium; Integration of Renal Mechanisms for Control of Blood Volume and Extracellular Fluid Volume

Pressure Diuresis & Natriuresis importance in BV and ECF control Directly UO BP Indirectly

Pressure Natriuresis and Diuresis Are Key Components of a Renal ‐ Body Fluid Feedback for Regulating Body Fluid Volumes and Arterial Pressure

BV BP UO CO

Factors Increase the Effectiveness of Renal-Body Fluid Feedback Control � Neural control � AgII � Aldostrone � ADH � ANP

Factors affect K secretion: [K]o Aldostrone Tubular flow Acidosis

30: Regulation of Acid ‐ Base Balance

extremely low pH: is not linear but logarithmic function ie, more change in acidemia normal range of arterial pH: 7.37 to 7.42 Volatile acids: CO2 carbonic anhydrase Non ‐ Volatile acids: H2SO4, H3PO4 β‐ hydroxybutyric acid, Acetoacetic acid Lactic acid Salcylic acid, formic acid Gycolic acid, oxalic acid

Isohydric law

Acetazolamide brush border carbonic anhydrase 2 1 5 4 3 no net secretion of H + little change in tubular fluid pH

DT, CT

Acid-base nomogram

Micturition (Voiding or Urination) • Bladder can hold 250 ‐ 400ml • Greater volumes stretch bladder walls initiates micturation reflex: • Spinal reflex – Parasympathetic stimulation causes bladder to contract – Internal sphincter opens – External sphincter relaxes due to inhibition

Urination: Micturation reflex Figure 19-18: The micturition reflex

Micturition (Voiding or Urination) Figure 25.20a, b