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					BIO – 2012 Human Anatomy & Physiology                                               Gyurkovics
4 credits

                                     FLUID, ELECTROLYTE,
                                    AND ACID-BASE BALANCE
                                                      Ch. 27
I. BODY FLUIDS
      Body H2O content:          50% - 60%
      Fluid Compartments: (ICF + ECF)
              Intracellular Fluid – in the cells
              Extracellular Fluid - Interstitial: lymph, CSF, humors, serous, synovial, GI.
                                    -Plasma
      Composition of Body Fluids
              Nonelectrolytes: don’t dissociate in solution => no electric charge
                        Glucose, lipids, creatinin, urea
              Electrolytes: do dissociate – salts, acids, bases, some proteins
                        Greater osmotic power (b/c of dissociation => more particles)
                                 Electrolyte Concentration: mEq/L = cc.Ion/atomic weight x charge
      Comparison of              ECF       –         ICF
              Major Kation        Na+                 K+
                                     -
              Major Anion         Cl                  HPO42- ,proteins
      Fluid Movement Among Compartments – regulated by HP and OP
                        (cc. of ECF determines Vol. of ICF)

II. WATER BALANCE (intake – output balance)
       Water Intake Regulation: by Hypothalamus (our old friend)
               Stimulus: - Vol. Plasma
                         - Osmolality of Plasma            picked up by osmoreceptors
       Water Output Regulation: by the kidneys – ADH release inhibited
       Disorders of Water Balance:
               Dehydration – negative fluid balance (causes + result)
               Hypotonic Hydration – Na+ deficit or too much H2O => ADH release inhibited
                                          can cause cerebral edema
               Edema – atypical accumulation of IF fluid (swelling)                            Hypoprotenemia
                       Factors accelerate: BP, capillary permeability, venous valves, vessel blockage, etc.

III. ELECTROLYTE BALANCE (Na+, K+, Ca++, Mg++, P3,5+ ) – intake - loss
        Role of Na+ in fluid Electrolyte Balance (ECF)
                Main cause of Osmotic Pressure! => Na+  Vol. Plasma, BP, Vol.ICF, Vol.ECF
                          Because cell membrane is impermeable to Na+  H2O has to adjust
        Regulation of Na+ Balance (65% is reabsorbed in PCT, 25% in Henle)                         Addison’s
                1. Aldosterone – trigger: Renin-Angiotensin II.
                2. Sympathetic adjustment: cardiovascular System’s Baroreceptors – trigger: BP
                3. ADH – trigger: ECF solute concentration picket up by osmoreceptors in Hypothalamus
                4. ANP – trigger: BP in atria (stretch receptors)
                5. Other Hormones:
                          Estrogen         Progesterone              Glucocorticoids

        Regulation of K+ Balance (ICF)
                Role: neuromuscular functions
                    Too Much in ECF  Hyperkalemia resting potential  depolarizations
                    Too Little in ECF  HypokalemiaHyperpolarization=>nonresponsiveness=>cardiac arrest
                Regulatory Site: collecting ducts, mainly secretion
                                  Factors, determine: cc.K+ of plasma (ECF) – Aldosterone
                         ++       +++
        Regulation of Ca and P Balance (stored mainly in bones: CaPO4)
                Role: normal blood clotting, membranes permeability, neuromuscular excitability
                         Hypocalcemia muscle tetany
                         Hypercalcemia skeletal, cardiac cells inhibited, arrhythmia
BIO – 2012 Human Anatomy & Physiology                                                  Gyurkovics
4 credits

                Influence of PTH: Ca++ Bone: osteoclast activity
                                           Small Intestine: Ca++ absorption,
                                           Kidneys: Ca++ reabsorption, PO4--, make of vitamin D
                Influence of Calcitonin: Ca++ Bone: osteoblast activity
        Regulation of Mg++ Balance
                Role: ICF kation, activates coenzymes for carbs and protein metabolism.
                      Neurotransmission, neuromuscular activity
                Most of them reabsorped
        Anion regulation (Cl-, etc.) – same mechanisms that regulate kations

IV. ACID – BASE BALANCE (Buffer Systems + Respiratory System + Renal Mechanisms)
                Origin of H+: P-containing proteins, phosphoric acid, ketone bodies, lactic acid
       1. Buffer Systems
                Bicarbonate Buffers  H2CO3-weak acid, NaHCO3-weak base
                Phosphate Buffers  NaH2PO4-weak acid, Na2HPO4-weak base
                Protein Buffers NH3+-R-COO-
       2. Respiratory System Regulation – slower but more effective
                pHmedullaRR, pHrespiratory center is depressed RR
       3. Renal Mechanisms – only for phosphoric acid, uric acid, lactic acid, ketone bodies (metabolic acids)
                HCO3- reabsorption
                Generating New HCO3- - by excretion of H+ and NH4+
                HCO3- Secretion – when body is in alkalosis

        Abnormalities of Acid-Base Balance
                         Respiratory Acidosis
                         Respiratory Alkalosis
                         Metabolic Acidosis
                         Metabolic Alkalosis

                 Effects of Acidosis and Alkalosis
                 Compensations
                          Respiratory
                          Renal

V. DEVELOPMENTAL ASPECTS


HW: Chapter 27 Homework

				
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