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Title: FLUIDELECTROLYTE AND


1
CHAPTER 19
  • FLUID-ELECTROLYTE AND
  • ACID-BASE BALANCE

2
  • Water makes up 55 to 75 of the total body
    weight
  • Electrolytes are ions found in body fluids most
    are minerals Na, K, Cl-
  • H, etc

3
WATER COMPARTMENTSfig 19-1
  • Intracellular fluid (ICF) water within cells
    about 2/3 of total body water
  • Extracellular fluid (ECF) water outside cells
    includes plasma, lymph, tissue fluid,
    specialized fluids
  • Water is constantly moving between the different
    compartments
  • Filtration- movement of molecules from an area of
    greater concentration to an area of lower
    concentration
  • Osmosis water will diffuse through membranes to
    areas of greater electrolyte concentration and/or
    lower concentration of water
  • Osmolarity measurement of concentration of
    dissolved materials in a solution
  • Box 19-1

4
Water Intake and OutputTable 19-1
  • Intake
  • fluids-1600ml/day
  • food-700ml/day
  • metabolic water product of cell
    respiration-200ml/day
  • Total 2500 ml
  • Output
  • urine-1500ml/day
  • sweat-500ml/day
  • exhaled air-300ml/day
  • feces-200ml/day
  • Total 2500 ml/day
  • Water intake output must be equal or there will
    be a loss of homeostasis

5
Regulation of Water IO
  • Osmoreceptors in the hypothalamus in the brain
    detect changes in osmolarity of body fluids,
    either too little/dehydration too
    much/overhydration
  • Dehydration
  • thirst sensation
  • ADH secreted increases reabsorption of water
  • aldosterone stimulates reabsorption of Na, thus
    water follows
  • Overhydration
  • ADH production decreases, output increases
  • ANH atrial natriuretic hormone secreted by
    the atria of the heart promotes loss of Na
    water follows

6
ELECTROLYTES
  • Chemicals that dissolve in water dissociate
    into ions
  • Positive ions or cations Na, K
  • Negative ions or anions Cl-, HCO3-, or bicarb
  • Electrolytes regulate the movement of water
    between compartments by affecting their osmotic
    pressure which is when 2 solutions of different
    concentrations are separated by a selectively
    permeable membrane. Remember water goes into the
    area of lesser concentration of water or greater
    concentration of dissolved particles in order to
    dilute or equal it out

7
ELECTROLYTES IN BODY FLUIDS-table 19-2
  • Intracellular fluid
  • K most abundant cation
  • Extracellular fluids
  • Na most abundant cation in both plasma and
    tissue fluid

8
Intake, Output Regulation of Electrolytes
  • Electrolyte intake part of foods beverages
  • Electrolyte output urine, sweat, feces
  • Regulated by hormones aldosterone, ANH (atrial
    natriuretic hormone), PTH (parathyroid hormone)
  • See box 19-2 electrolyte imbalances

9
Acid-Base Balance
  • Normal pH range for blood 7.35 to 7.45
  • Normal pH of body fluids is maintained by the
    buffer systems in body fluids, respirations the
    kidneys

10
Buffer Systems
  • Consists of a weak acid a weak base react with
    strong acids or bases to change them to
    substances that dont greatly affect pH.
  • Bicarbonate buffer system
  • carbonic acid, H2CO3, a weak acid
  • sodium bicarbonate, NaHCO3, a weak base
  • works in both blood tissue fluid

11
Respiratory Mechanisms
  • Changes pH by regulating the amount of CO2 in
    body fluids, usually works in about 1-3 minutes.
    (The higher the CO2 content the higher the H ion
    concentration, the lower the pH
  • See page 32 in AP book for pH scale.
  • Respiratory disease may cause a pH change
  • Changes in pH caused by other than a respiratory
    disorder are called metabolic acidosis or
    alkalosis
  • The respiratory system may compensate for a
    metabolic pH change
  • See table 19-3

12
Renal Mechanisms
  • The most effective at changing pH, but may take
    several hours to days to work
  • In response to acidosis, the kidneys will excrete
    H ions retain Na HCO3- ions or bicarbonate
  • In response to alkalosis, the kidneys will retain
    H ions excrete Na HCO3- ions

13
Effects of pH Changes
  • Acidosis depresses synaptic transmission in the
    CNS causing confusion, coma death
  • Alkalosis increases synaptic transmission in
    the CNS PNS causing irritability, muscle spasms
    convulsions
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