Transcript Anatomy & Physiology SIXTH EDITION Chapter 27, part 1 Fluid, Electrolyte, and Acid-Base Balance PowerPoint® Lecture Slide Presentation prepared by Dr.

Anatomy & Physiology
SIXTH EDITION
Chapter 27, part 1
Fluid, Electrolyte, and
Acid-Base Balance
PowerPoint® Lecture Slide Presentation prepared by
Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Frederic H. Martini
Fundamentals of
Learning Objectives
• Explain what is meant by “fluid balance,”
“electrolyte balance,” and “acid-base balance”
• Compare the compositions of intracellular and
extracellular fluids
• Identify the hormones that play important roles
in regulating fluid and electrolyte balance
• Describe the movement of fluid that takes place
within the ECF, between the ECF and the ICF,
and between the ECF and the environment
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Learning Objectives
• Discuss how sodium, potassium, calcium and
chloride ions are regulated to maintain
electrolyte balance
• Explain the buffering systems that balance the
pH of the intracellular and extracellular fluids
• Describe the compensatory mechanisms
involved in acid-base balance
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SECTION 27-1
Fluid, Electrolyte and Acid-base Balance:
An Overview
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Maintenance of normal fluid volume and
composition is vital
• Extracellular fluid (ECF)
• Interstitial fluid, plasma, and other body fluids
• Intracellular fluid (ICF)
• The cytosol
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Fluid and electrolyte balance
• Fluid balance
• The amount of water gained each day equals
the amount lost
• Electrolyte balance
• The ion gain each day equals the ion loss
• Acid-base balance
• H+ gain is offset by their loss
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SECTION 27-2
An Introduction to Fluid and Electrolyte
Balance
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The ECF and the ICF are two distinct fluid
compartment
• ICF
• The cytosol of cells
• Makes up about two-thirds of the total body
water
• ECF
• Major components include the interstitial fluid
and plasma
• Minor components include all other
extracellular fluids
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Figure 27.1 The Composition of the Human
Body
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Figure 27.1a
Regulation of fluids and electrolytes
• Homeostatic mechanisms respond to changes in
ECF
• No receptors directly monitor fluid or electrolyte
balance
• Respond to changes in plasma volume or
osmotic concentrations
• All water moves passively in response to
osmotic gradients
• Body content of water or electrolytes rises if
intake exceeds outflow
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Figure 27.2 Cations and Anions in Body Fluids
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Figure 27.2
Primary regulatory hormones
• Antidiuretic hormone (ADH)
• Stimulates water conservation and the thirst
center
• Aldosterone
• Controls Na+ absorption and K+ loss along the
DCT
• Natriuretic peptides (ANP and BNP)
• Reduce thirst and block the release of ADH
and aldosterone
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Interplay between fluid balance and electrolyte
balance
• Different mechanisms regulate fluid and
electrolyte balance
• This distinction is vital in the clinical setting
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SECTION 27-3
Fluid Balance
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Fluid movement within the ECF
• Fluid moves freely within ECF compartment
• Water losses are normally balanced by gains
• Eating
• Drinking
• Metabolic generation
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Figure 27.3 Fluid Exchanges
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Figure 27.3
Fluid exchange with the environment
• The major routes of fluid exchange with the
environment include:
• Water loss
• Temperature rise from fever
• Water gains
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Water excess and depletion
• Hyponatremia
• Na+ concentration in the ECF is reduced
(overhydration)
• Hypernatremia
• Na+ in the ECF is abnormally high
• Dehydration
• Develops when water loss outpaces water gains
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Fluid shifts
• Water movement between ECF and ICF
• If ECF becomes hypertonic relative to ICF,
water moves from ICF to ECF
• If ECF becomes hypotonic relative to ICF,
mater moves from ECF into cells
PLAY
Animation: Introduction to Body Fluids
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SECTION 27-4
Electrolyte Balance
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Problems with Electrolyte Balance
• Usually result from sodium ion imbalances
• Potassium imbalances are less common, but
more dangerous
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Sodium balance
• Rate of sodium uptake across digestive tract
directly proportional to dietary intake
• Sodium losses occur through urine and
perspiration
• Shifts in sodium balance result in expansion or
contraction of ECF
• Large variations corrected by homeostatic
mechanisms
• Too low, ADH / aldosterone secreted
• Too high, ANP secreted
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Figure 27.4 The Homeostatic Regulation of
Normal Sodium Ion Concentrations in Body
Fluids
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Figure 27.4
Figure 27.5 The Integration of Fluid Volume
Regulation and Sodium Ion Concentrations in
Body Fluids
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Figure 27.5
Potassium balance
• Potassium ion concentrations in ECF are low
• Not as closely regulated as sodium
• Potassium ion excretion increases as
• ECF concentrations rise
• Aldosterone secreted
• pH rises
• Potassium retention occurs when pH falls
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ECF Concentrations of other electrolytes
• Calcium balance
• Bone reserves, absorption in the digestive
tract, and loss at kidneys
• Magnesium balance
• Absorbed by the PCT to keep pace with urinary
losses
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ECF Concentrations of other electrolytes
• Phosphate balance
• Absorbed by the PCT in response to calcitriol
• Chloride balance
• Absorbed at digestive tract to balance losses in
urine and sweat
PLAY
Animation: Electrolyte homeostasis
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