Lecture Notes Menu Water Electrolytes


INTRODUCTION

  1. WATER, ACID, BASE, AND ELECTROLYTE LEVELS ARE MAINTAINED IN A NARROW RANGE OF CONCENTRATION

  2. THE URINARY, RESPIRATORY, GASTROINTESTINAL, INTEGUMENTARY, NERVOUS, AND ENDOCRINE FUNCTION IN:

    1. FLUID BALANCE
    2. ELECTROLYTE BALANCE
    3. AND pH BALANCE

  3. INTRACELLULAR IS INSIDE A CELL

  4. EXTRACELLULAR IS OUTSIDE THE CELL, IT CONTAINS :

1. INTERSTITAL FLUID
2. PLASMA

II. REGULATION OF INTRACELLUAR FLUID

  1. DETERMINED BY SUBSTANCES USED OR PRODUCED IN THE CELL AND SUBSTANCES EXCHANGED WITH THE EXTRA CELLULAR FLUID

  2. INTRACELLULAR DIFFERS FROM EXTRACELLULAR FLUID BECAUSE OF THE CELL MEMBRANE

  3. WATER MOVEMENT DEPENDS ON DIFFERENCES BETWEEN THE INTRA AND EXTRA CELLULAR FLUIDS.

III. REGULATION OF EXTRACELLULAR FLUIDS


  1. DETERMINED BY THE INTAKE AND ELIMINATION OF SUBSTANCES FROM THE BODY

  2. ALSO THE EXCHANGE BETWEEN EXTRA AND INTRA CELLULAR FLUIDS

IV. REGULATION OF ION CONCENTRATION
  1. CATIONS AND ANIONS ARE REFERRED TO AS ELECTROLYTES


    1. ANIONS ARE NEG. CHARGED

    2. CATIONS ARE POS. CHARGED

    3. IONS HAVE ELECTRICAL CHARGES

    EX. Na + Cl = NaCl


  2. Na IS RESPONSIBLE FOR 90 - 95 % OF EXTRACELLULAR OSMOTIC PRESSURE

  3. THE AMOUNT OF Na EXCRETED BY THE KIDNEY IS THE DIFFERENCE BETWEEN


    1. THE AMOUNT THAT ENTERS THE NEPHRON

    2. THE AMOUNT THAT RESORBED

    3. GFR DETERMINES THE AMOUNT THAT ENTERS

    4. ALDOSTERONE DETERMINES RESORPTION

  4. SMALL QUANTITIES OF Na ARE LOST IN SWEAT

  5. INCREASED B.P. INCREASES WATER AND SALT LOSS

    1. BARORECEPTOR REFLEXES REDUCE ADH ECRETION

    2. RENIN SECRETION IN INHIBITED - LESS ALDO.


  6. THE MECHANISMS THAT REGULATE Na IN EXTRACELLULAR FLUID DO NOT DIRECTLY MONITOR Na AMOUNTS, RATHER :


    1. SENSITIVITY TO B.P.

    2. EXTRACELLULAR FLUID OSMALITY

    3. THE BARORECEPTORS ARE LOCATED IN :

    ATRIA

    VENA CAVA

    AORTIC ARCH

    CAROTID SINUS

    4. RESPOND TO STRETCHING AND PRESSURE

    5. SIGNAL HYPOTHALAMUS TO REDUCE ADH SECRETION³


    V. CHLORIDE IONS ( Cl- ) A. CHLORIDE IONS

    ARE THE DOMINANT ANION IN THE EXTRACELLULAR FLUID

    VI. POTASSIUM IONS ( K+)

    1. EXTRACELLULAR CONCENTRATION OF K AFFECTS RESTING MEMBRANE POTENTIAL

    2. AMOUNT OF K EXCRETED DEPENDS ON :

      1. AMOUNT ENTERING THE GLOMERULAR FILTRATE

      2. AMOUNT ACTIVELY RESORBED BY THE NEPHRON

      3. AMOUNT SECRETED INTO THE DISTAL TUBULE

    3. ALDOSTERONE INCREASES K SECRETION


      VII. CALCIUM IONS

    1. ELEVATED EXTRACELLULAR CALCIUM LEVELS PREVENT MEMBRANE DEPOLARIZATION

      1. DECREASES PERMEABILITY OF MEMBRANES TO Na

      2. PREVENTS NORMAL DEPOLARIZATION NERVE, MUSCLE

    2. DECREASED LEVELS LEAD TO SPONTANEOUS ACTION POTENTIAL GENERATION

      1. ELEVATED PERMEABILITY OF MEMBRANES

      2. RESULTS IN SPONTANEOUS ACTION POTENTIALS

    3. PARATHYROID HORMONE INCREASES EXTRACELLULAR CALCIUM LEVELS

      1. HORMONE DECREASES EXTRACELLULAR PHOSPHATE

      2. STIMULATES OSTEOCLAST ACTIVITY

      3. INCREASES CALCIUM ABSORPTION FROM KIDNEY

      4. STIMULATES ACTIVE VITAMIN D PRODUCTION

      ( 1,25- HYDROXYCHOLECALCIFEROL )

    4. VITAMIN D STIMULATES CALCIUM UPTAKE FROM THE INTESTINE

    5. CALCITONIN DECREASES EXTRACELLULAR CALCIUM LEVELS

      1. SECRETED BY THE PARAFOLLICULAR CELLS- THYROID

      2. INCREASES OSTEOBLAST ACTIVITY

      3. INHIBITS BONE DEMINERILIZATION

    VIII. REGULATION OF WATER CONTENT

    1. WATER CROSSES THE G.I. TRACT BY OSMOSIS

    2. SENSE OF THIRST IS STIMULATED BY

      1. INCREASED EXTRA CELLULAR OSMALITY

      2. OR A DECREASE IN BLOOD PRESSURE

    3. ROUTES OF WATER LOSS

      1. EVAPORATION FROM RESPIRATORY AND SKIN

      2. WATER LOSS IN GI TRACT IS USUALLY SMALL

      3. VOMITING OR DIARRHEA CAN INCREASE LOSS

      4. KIDNEYS ARE THE PRIMARY EXCRETOR OF WATER

      IX. ACID / BASE BALANCE

      1. AN ACID RELEASES HYDROGEN IONS INTO SOLUTION

      2. A BASE REMOVES THEM

      3. ACIDOSIS AND ALKALOSIS

        1. NORMAL BLOOD pH IS 7.35 TO 7.45

        2. ACIDOSIS IS pH BELOW

        3. ALKALOSIS IS pH ABOVE

      X. BUFFER SYSTEMS

      1. A BUFFER RESISTS CHANGES IN pH

        1. WHEN H+ ARE ADDED A BUFFER REMOVES THEM

        2. WHEN H+ ARE REMOVED A BUFFER REPLACES THEM

      2. PROTEINS, BICARBONATE - CARBONIC ACID, PHOSPHATE ARE COMMON BUFFERS

        XI. MECHANISM OF ACID BASE REGULATION

        1. RESPIRATORY REGULATION IS ACHIEVED BY CARBONIC ACID / BI CARBONATE BUFFER SYSTEM


          1. AS CO2 INCREASES, SO DOES ACIDITY

          2. AS CO2 DECREASES, ACIDITY DECREASES

          3. CO2 AND pH AFFECT RESPIRATORY CENTERS

          4. ( MEDULLARY RESPIRATORY CENTER )

          5. REACTIONS BETWEEN CO2 AND WATER IS CATALYZE

            BY CARBONIC ANHYDRASE

          6. CARBONIC ANHYDRASE IS FOUND IN R.B.C.

          7. HYPOVENTILATION INCREASES BLOOD CO2

          8. HYPERVENTILATION DECREASES BLOOD CO2

            B. THE URINARY SYSTEM

            1. LOSS OF H+ IONS TO URINE AND GAIN OF BICARBONATE CAUSE EXTRACELLULAR pH TO INCREASE

            FUNCTION IS DESCRIBED AS FOLLOWS

            CARBONIC DISSOCIATES TO FORM H+ AND BICARBONATE

            ACTIVE TRANSPORT PUMPS H+ INTO NEPHRON LUMEN

            Na IS ACTIVELY PUMPED INTO NEPHRON CELL

            Na AND BICARBONATE DIFFUSE INTO THE EXTRACELLULAR FLUID

            BICARBONATE IONS ARE REABSORBED

            BICARBONATE COMBINES WITH H+ TO FORM CARBONIC ACID

            CARBONIC ACID FORMS CO2 AND WATER

            CO2 DIFFUSES INTO THE NEPHRON AND FORMS CARBONIC ACID

            WHICH DISASSOCIATES TO FORM BICARBONATE AND H+

            BICARBONATE DIFFUSE INTO THE EXTRACELLULAR FLUID

            H+ IS PUMPED INTO THE LUMEN OF THE NEPHRON ( TUBULE )