fluid and electrolytes Flashcards
a delicate balance of fluids, electrolytes, and acids and bases maintained in the body
HOMEOSTASIS
approximately 60% of average healthy adult’s weight (70% to 80% in infants and 50% to people older than 50)
Water
Water is the primary
body fluid
TWO COMPARTMENTS OF BODY’S FLUID
INTRACELLULAR FLUID (ICF)
EXTRACELLULAR FLUID (ECF)
found within the cells of the body; 2/3 of the total body fluid in adults
INTRACELLULAR FLUID (ICF)
found outside the cells; 1/3 of the total body fluid
EXTRACELLULAR FLUID (ECF)
20% of the ECF; found within the vascular system
INTRAVASCULAR FLUID (PLASMA)
75% of the ECF; surrounds the cells
INTERSTITIAL FLUID
charged particles
ions
ions that carry a positive charge
cations
ions that carry a negative charge
anions
minerals in the body that have electrical charge; chemicals from which ions are made
Electrolytes
are generally measured in milliequivalents per Liter of water (mEq/L) or milligrams per 100 milliliters (mg/100mL)
electrolytes
Sodium (Na+)
Potassium (K+)
Calcium (Ca++)
Magnesium (Mg++)
cations
Chloride (Cl-)
Bicarbonate (HCO3-)
Phosphate (HPO4–)
Sulfate (SO4–)
anions
selectively permeable/semi-permeable to solutes
membranes
MOVEMENT OF BODY FLUIDS AND ELECTROLYTES
Osmosis
Diffusion
Filtration
Active Transport
Movement of water across cell membranes, from the less concentrated solution to the more concentrated solution
osmosis
substances
dissolved in a liquid
solute
component that
can dissolve a solute
solvent
the concentration of solutes in body fluids; solute per kilogram of water
OSMOLALITY
power of a solution to draw water across a semipermeable membrane
OSMOTIC PRESSURE
pulls water from the interstitial space into the vascular compartment
COLLOID OSMOTIC PRESSURE (ONCOTIC PRESSURE)
solute and solvent are equal
Isotonic solution
higher osmolality than body fluids; cells shrink
Hypertonic solution
lower osmolality than body fluids; cells swell
Hypotonic solution
Movement of molecules through a semipermeable membrane from an area of higher concentration to an area of lower concentration
diffusion
Fluid and solutes move together across a membranes from an area of higher pressure to one of lower pressure.
filtration
pressure in the compartment that results in the movement.
Filtration pressure
pressure
exerted by a fluid within a
closed system on the walls
of the container in which it is
contained.
Hydrostatic pressure
Substances can move across cell membranes from a less concentrated solution to a more concentrated one
ACTIVE TRANSPORT
It differs from diffusion and osmosis
in that metabolic energy is expended
ACTIVE TRANSPORT
A substance combines with a carrier on the outside surface of the cell membrane.
ACTIVE TRANSPORT
Fluid Intake
Fluid Output
Maintaining Homeostasis
REGULATING BODY FLUIDS
An average adult needs 2,500 mL per day.
fluid intake
amount in oral fluids
1,200 to 1,500 mL
amount in Water in foods
1,000 mL
amount Water as by-product of food metabolism
200 mL
total amount intake
2,400 to 2,700 mL
it takes 30 minutes to 1 hour for the fluid to be absorbed and distributed throughout the body
Thirst mechanism
primary regulator of fluid intake
- thirst center is located in the hypothalamus of the brain.
Thirst mechanism
Fluid losses that counterbalance the adult’s 2,500-mL average fluid intake.
fluid output
amount in urine
1,400 to 1,500 mL
amount in Insensible Losses
Lungs (water vapor in the expired air)
Skin
350 mL to 400 mL
amount in Sweat
100 mL
amount in Feces
100 mL to 200 mL
total amount output
2,300-2,600 mL
Homeostatic regulators/mechanisms:
- Kidneys
- Antidiuretic Hormone
- Renin-Angiotensin-Aldosterone System
- Atrial Natriuretic Factor
Primary regulator of body fluids and electrolyte balance.
kidneys
Regulates water and electrolyte secretion
kidneys
Plays a significant role in acid-base regulation, excreting hydrogen ion (H+) and retaining bicarbonate.
kidneys
Regulates water excretion from the kidney
Antidiuretic Hormone (ADH)
Produced when serum osmolality rises; conversely, ADH is suppressed when serum osmolality decreases
Antidiuretic Hormone (ADH)
Synthesized in the anterior portion of the hypothalamus
Antidiuretic Hormone (ADH)
Restore blood volume (and renal perfusion) through sodium and water retention
Renin-Angiotensin-Aldosterone System
- When blood flow or pressure to kidneys decreases, renin is released.
- Renin causes the conversion of angiotensin to angiotensin I, which is converted to angiotensin II by angiotensin-converting enzyme.
3.Angiotensin II acts directly on the nephrons to promote Sodium and water retention.
4.Stimulates the release of Aldosterone from the adrenal cortex. It promotes sodium retention.
Renin-Angiotensin-Aldosterone System
Released from cells in the atrium of the heart in response to excess blood volume and stretching the atrial walls.
Atrial Natriuretic Factor (ANF)
Promotes sodium wasting and acts as a potent diuretic, thus reducing vascular volume.
Atrial Natriuretic Factor (ANF)
Reduces thirst, reducing fluid intake
Atrial Natriuretic Factor (ANF)
Importance of electrolytes:
Maintaining fluid balance
Contributing to acid-base regulation
Facilitating enzyme reactions
Transmitting neuromuscular reactions