MedSurg Week 3 Textbook Notes
Chapters 19, 32 & 33
Only 19 finished
Chapter 19: Fluid, Electrolyte and Acid-Base Imbalances (pp. 342-367)
Homeostasis: the state of equilibrium in the internal environment of the body, naturally
maintained by adaptive responses that promote health survival.
Maintenance of the composition and volume of body fluids, electrolytes and acid-base
concentrations within narrow normal limits is necessary to maintain homeostasis.
Water Content of the Body:
- Water is the primary component of the body, accounting for 60% of adult body
weight. It varies with sex, body mass and age.
- Lean body mass (muscle) has a higher percentage of water than adipose tissue
(fat). Therefore, more fat = less water.
- In older people, they have a lower % of body water because of decreased
muscle mass with age and increased fat. Therefore, older people are at an
increased risk for fluid-related problems
Body Fluid Compartments:
- The 2 major fluid compartments in the body are intracellular spaces (inside the
cells) and the extracellular spaces (outside the cells).
- ~⅔ of body water is located within cells and is called intracellular fluid (ICF).
- Extracellular fluid (ECF) consists primarily of interstitial fluid and intravascular
fluid (plasma). The ECF constitutes ⅓ of the body water.
- Transcellular fluids are the fluid that fills up the spaces of chambers that are
created or formed from the linings of epithelial cells (cerebrospinal fluid, fluid in
the GI tract and joint spaces, resp. secretions, etc).
1L of water = 1 kg, therefore body weight change, especially sudden change, is an
excellent indicator of overall fluid volume loss or gain.
Electrolytes: substances whose molecules dissociate or split into ions when placed in
solution. Ions are electrically charged molecules.
Cations are positively charged ions (K+, Na+, CA2+, Mg2+).
Anions are negatively charged ions (HCO3-, Cl-, PO43-). Most proteins.
, Electrical charge is called valence.
Mechanisms Controlling Fluid & Electrolyte Movement: Processes such as diffusion
are involved in the movement of electrolytes and water between the ICF and the ECF.
Water movement is driven by two forces: hydrostatic and osmotic pressure.
Diffusion: the movement of molecules from an area of high concentration to one of low
concentration.
- Net movement of molecules stops when the concentrations are equal in both
areas.
- Simple diffusion requires no external energy.
Facilitated Diffusion: uses a protein carrier in the cell membrane. The protein carrier
combines with a molecule and assists in moving the molecule across the membrane
from high conc. to low conc. Ex: glucose transport into the cell.
Osmosis: the movement of water between 2 compartments separated by a
semipermeable membrane, one that allows the movement of water, but not solute.
- Water moves through the membrane from an area of low solute concentration to
an area of high solute concentration.
- Requires no outside energy sources
- High water = low solute, Low water = lots of solute.
Osmotic Pressure: the amount of pressure necessary to stop the osmotic flow of
water.
- Draws fluids in and keeps it there.
- Determined by the concentration of solutes in solution.
Osmolarity: measurement of solute. Number of solute particles per 1L of solvent.
Osmolality: measurement of solute. Number of solute particles per 1kg of solvent.
Hypotonic: solute less concentrated than they are in cells/another solution. Causes
cells to swell.
Isotonic: same osmolality/concentration as the cell interior/another solution. Keeps cell
the same.
Hypertonic: solutions more concentrated than they are in cells/another solution.
Causes cells to shrink and eventually lyse.
Chapters 19, 32 & 33
Only 19 finished
Chapter 19: Fluid, Electrolyte and Acid-Base Imbalances (pp. 342-367)
Homeostasis: the state of equilibrium in the internal environment of the body, naturally
maintained by adaptive responses that promote health survival.
Maintenance of the composition and volume of body fluids, electrolytes and acid-base
concentrations within narrow normal limits is necessary to maintain homeostasis.
Water Content of the Body:
- Water is the primary component of the body, accounting for 60% of adult body
weight. It varies with sex, body mass and age.
- Lean body mass (muscle) has a higher percentage of water than adipose tissue
(fat). Therefore, more fat = less water.
- In older people, they have a lower % of body water because of decreased
muscle mass with age and increased fat. Therefore, older people are at an
increased risk for fluid-related problems
Body Fluid Compartments:
- The 2 major fluid compartments in the body are intracellular spaces (inside the
cells) and the extracellular spaces (outside the cells).
- ~⅔ of body water is located within cells and is called intracellular fluid (ICF).
- Extracellular fluid (ECF) consists primarily of interstitial fluid and intravascular
fluid (plasma). The ECF constitutes ⅓ of the body water.
- Transcellular fluids are the fluid that fills up the spaces of chambers that are
created or formed from the linings of epithelial cells (cerebrospinal fluid, fluid in
the GI tract and joint spaces, resp. secretions, etc).
1L of water = 1 kg, therefore body weight change, especially sudden change, is an
excellent indicator of overall fluid volume loss or gain.
Electrolytes: substances whose molecules dissociate or split into ions when placed in
solution. Ions are electrically charged molecules.
Cations are positively charged ions (K+, Na+, CA2+, Mg2+).
Anions are negatively charged ions (HCO3-, Cl-, PO43-). Most proteins.
, Electrical charge is called valence.
Mechanisms Controlling Fluid & Electrolyte Movement: Processes such as diffusion
are involved in the movement of electrolytes and water between the ICF and the ECF.
Water movement is driven by two forces: hydrostatic and osmotic pressure.
Diffusion: the movement of molecules from an area of high concentration to one of low
concentration.
- Net movement of molecules stops when the concentrations are equal in both
areas.
- Simple diffusion requires no external energy.
Facilitated Diffusion: uses a protein carrier in the cell membrane. The protein carrier
combines with a molecule and assists in moving the molecule across the membrane
from high conc. to low conc. Ex: glucose transport into the cell.
Osmosis: the movement of water between 2 compartments separated by a
semipermeable membrane, one that allows the movement of water, but not solute.
- Water moves through the membrane from an area of low solute concentration to
an area of high solute concentration.
- Requires no outside energy sources
- High water = low solute, Low water = lots of solute.
Osmotic Pressure: the amount of pressure necessary to stop the osmotic flow of
water.
- Draws fluids in and keeps it there.
- Determined by the concentration of solutes in solution.
Osmolarity: measurement of solute. Number of solute particles per 1L of solvent.
Osmolality: measurement of solute. Number of solute particles per 1kg of solvent.
Hypotonic: solute less concentrated than they are in cells/another solution. Causes
cells to swell.
Isotonic: same osmolality/concentration as the cell interior/another solution. Keeps cell
the same.
Hypertonic: solutions more concentrated than they are in cells/another solution.
Causes cells to shrink and eventually lyse.
