Presentation on theme: "Integrative Physiology II: Fluid and Electrolyte Balance"— Presentation transcript:
1 Integrative Physiology II: Fluid and Electrolyte Balance Chapter 20Integrative Physiology II: Fluid and Electrolyte Balance
2 Figure 20-3: Role of the kidneys in water balance Body Water BalanceUrine concentration:Dilute: 300 mOsMConcentrated: 1200 mOsMFigure 20-3: Role of the kidneys in water balance
3 What is “put back” and where in the nephron. Proximal tubuleGlucose (those carriers) & Na+ (Primary active transport) urea (passive transport)Loop of HenleH2O and ions ( Na+, K+ & Cl-)Distal tubuleNa+ & H2OCollecting ductH2O, Na+ & urea (again)
4 Overview: starts off isosmotic 300 mOsM (saltiness) Figure 20-4: Osmolarity changes as fluid flows through the nephron
5 VASOPRESSIN: If we NEED water, we can get it from the collecting duct!
6 Vasopressin (a.k.a. ADH) regulates urine OsM: Let’s make concentrated uring part I Figure 20-5: Water movement in the collecting duct in the presence and absence of vasopressin
7 Formation of Water Pores: Mechanism of Vasopressin Action
9 Figure 20-10: Countercurrent exchange in the medulla of the kidney Countercurrent exchanger. Loop of Henle Let’s make concentrated uring part IIMedullary osmotic gradient; more saltyCollecting ductFigure 20-10: Countercurrent exchange in the medulla of the kidney
10 Why is it, countercurrent? The players:Loop of HenleDescending/ascendingvasa rectaIons: which ones?H2OWhy is it, countercurrent?
11 Key facts:1. descending LOH is water permeable, ascending LOH is NOT.2. Ascending LOH actively pumps out ions.3. water goes to where the most stuff is!!!4. vasa recta removes water so it doesn’t dilute the medullary gradient.
12 SODIUM BALANCE:What happens to the body’s OsM after eating salty fries? Increase/decreaseThis triggers two responses; can you guess?
13 Vassopressin and thirst; both decrease OsM, but raise blood pressure. To lower blood pressure our kidneys excrete sodium.How does excreting sodium lower BP?
14 WATER GOES TO WHERE THE MOST STUFF IS. When sodium leaves, water follows, decreasing ECF volume, and BP.
15 Sodium Balance: Intake & Excretion Figure 20-11: Homeostatic responses to eating salt
16 Sodium is regulated by aldosterone from the adrenal cortex. Aldosterone is actually secreted in response to blood pressure, blood volume and OsM.More aldosterone: more sodium reabsorption.Aldosterone target: principal cell (P cell) of the distal tubule & collecting duct.
17 Mechanism of Na+ Selective Reabsorption in Collecting Duct !water does not follow!Vassopressin must be presentFigure 20-12: Aldosterone action in principal cells
18 How does aldosterone get released How does aldosterone get released? RAAS: renin-angiotensin-aldosterone-systemFigure 20-13: The renin-angiotensin-aldosterone pathway
24 Acid/Base Homeostasis Acidosis: plasma pHProtein damageCNS depressionAlkalosis: plasma pHHyperexcitabilityCNS & heartBuffers: HCO3- & proteinsH+ input: diet & metabolicH+ output: lungs & kidneyNeutral pH is 7.0Biological pH is 7.4Determined based upon H+ concentration.
25 Acid/Base Homeostasis: Overview Figure 20-18: Hydrogen balance in the body
26 Low pH – acidosis – nervous tissue becomes less exciteable – respiratory centers shut down. High pH – alkalosis – neurons become hyperexciteable – twitching, numbness – tetenay and paralyzed respiratory muscles.
27 pH homeostasis depends on 3 things: 1. buffers2. the lungs3. the kidneys
28 Buffer systems Bicarbonate, phosphate ions, and proteins (Hb) Buffers prevent significant changes in pH by binding or releasing H+CO2 + H2O H2CO3 H+ + HCO3-carbonic anhydrase
29 What will drive the equation to the right? What will drive the equation to the left?CO2 + H2O H2CO3 H+ + HCO3-carbonic anhydraseHow can ventilation compensate for pH disturbances? Pg. 647.
30 Acidosis prevention at the Proximal Tubule: H+ excreted, bicarbonate reabsorption. Na+ - H+ antiport activityGlutamine metabolismFigure 20-21: Proximal tubule secretion and reabsorption of filtered HCO3-
31 Kidney Hydrogen Ion Balancing: Collecting Duct Type A Intercalated cells excrete H+ absorb HCO3-Type B intercalated cells absorb H+ secrete HCO3-
32 Kidney Hydrogen Ion Balancing: Collecting Duct The polarity of the two cells is reversed with the transportproteins on opposite sides.Figure 20-22: Role of the intercalated cell in acidosis and alkalosis
33 Acid-base disturbances: respiratory or metabolic Respiratory acidosis –hypoventilation & CO2 retention.COPD- loss of alveolar tissueMetabolic acidosisMetabolic acids increase protonsLactic acid from anaerobic metabolism burn sugar not oxygen.Respiratory alkalosisHyperventilation rids CO2Hysterical hyperventilationRenal compensation can occurMetabolic alkalosisVomiting stomach acids and taking bicarbonate-containing antacids.Respiratory compensation takes place rapidly.