Basics Flashcards
Diffusion
Movement of solutes (electrolytes) from an area of greater concentration to an area of lower concentration
Think: food coloring being dropped into water
Osmosis
Movement of water across a semi- permeable membrane from an area of low solute concentration to an area of high solute concentration.
Think: you going to a crowded party!
Active transport
Movement of substances across cell membranes from an area of low concentration to high concentration using energy (ATP)
Think: pushing electrolytes uphill - requires energy!!
Filtration (Hydrostatic pressure)
The movement of fluid and small solutes through capillaries due to pressure differences.
Think: like squeezing sponge - pressure forces fluid out
Oncotic pressure (colloid osmotic pressure)
The pull exerted by proteins (especially albumin) to draw fluid back into the vessels.
Normal routes of body losing fluids
Renal (Urine)
Gl tract(feces)
Skin (perspiratIon).
Lungs( water vapor )
Abnormal routes of losing fluids and electrolytes
Vomiting, diarrhea, hemorrhage, drainage (tubes, wounds, fistulas)
What are the 2 main hormones that help regulate fluid balance through the kidneys
Antidiuretic hormone (adh)
Aldosterone
Antidiuretic hormone (ADH)
Released by the pituitary gland when the body senses a fluid deficit (dehydration or increased osmolality).
Signals kidneys to retain water, reducing urine output, which helps keep fluid levels stable
Think:ADH= Adds Da H2O back!
Aldosterone
Released by the adrenal glands.
Acts on the kidneys, promoting resorption of sodium and water, thus increasing blood volume and bp.
Think: ALDOsterone holds onto SALT, water follows salt!!
Why are infant at risk for fluid and electrolyte imbalances?
Higher metabolic rates
Immature kidneys
Higher fluid requirements relative to size
Larger body surface area compared to their size, leading to faster fluid losses through skin and breathing
Why are older adults at higher risk for fluid and electrolyte imbalances?
Blunted thirst sensation
↓ lean body mass
Reduces kidney function and ↓ ability to conserve water effectively
Often rely on others for hydration, especially if cognitive impairments are present.
What is the role of the kidneys in regulating fluid and electrolyte balance?
Adjust urine volume
* selectively reabsorb electrolytes keeping them in balance
* respond to hormones to maintain proper fluids and electrolyte levels.
Normal range of serum osmolality and what does it indicate about fluid balance?
Normal range: 275-295 mOsm/kg
Reflects concentration of particles (sodium, glucose, and urea) dissolved in your blood.
High is to dry (blood is too concentrated)
Low :blood is diluted, overhydration or fluidoverload.
Name 2 hormones produced by the heart that help regulate fluid balance and briefly explain how they work?
Atrial natriuretic peptide (ANP)
B-type natriuretic peptide (BNP)
These are released when ↑ pressure (due to too much fluid) in the hearts chambers. They help by:
* suppressing aldosterone, renin, and ADH.
* ↑ sodium and water excretion
* ↓ blood volume and bp.
Think: there is too fluid, lets get rid of it!!
Isotonic solution
Same concentration (osmolality) as body fluids
*Fluids doesn’t move in or out of cells; balanced
* example: normal saline (0.9% NaCl)
HypOtonic solutions
Lower concentration than body fluids
Water moves into cells, causing cells to swell (can get big, round, and possibly burst).
*Example: half-normal saline (0.45% NaCl)
HypOtonic → sells swell like an “O” (big and round)
HypErtonic solutions
Higher concentration than body fluids
*Water moves out of cells, causing cells to shrink (wrinkle up like raisins).
*example: 3% NaCl solution
HypErtonic → cells shrink and wrinklE
What is a third spacing- give an example of when it commonly occurs?
When fluid moves from blood vessels into spaces where it doesn’t belong or can’t return easily into circulation. Fluid becomes trapped outside of bloodstream.
Examples:
* burn injuries (fluid moves into burned tissues)
* ascites ( fluid collects into the abdominal cavity, often seen in liver disease)
* edema after trauma or surgery (fluid accumulates in tissue)
Think: fluid is hiding where shouldn’t be
When hydrostatic pressure is higher in the arterial end of a capillary bed, what direction does the fluid move into or out of the capillaries?
It pushes fluid out of the capillarIes into the interstitial space (the space between cells)
↑ hydrostatic pressure = fluid moves OUT of capillaries
At the venous end oncotic pressure?
Pulls fluid back into the capillaries.
What is oncotic pressure and what causes it?
The pulling force exerted by plasma proteins (mainly albumin) that draws fluid back into the capillaries from the interstitial space.
what are the four key characteristics of fluid balance?
Volume
Concentration (osmolality)
Composition (electrolyte concentration)
Acidity (pH)
WHAT PERCENTAGE OF THE TOTAL BODY WEIGHT IS FLUID IN A HEALTHY ADULT?
55 to 60%
What percentage of total body weight is fluid in an older adult?
50% to 55%
Name the compartments where body fluids are distributed
Intracellular fluid (ICF) and Extracellular fluid (ECF)
What is included in the extracellular compartment?
Intravascular fluid
Interstitial fluid
Transcellular fluids
