Water balance part 1 Flashcards
Life depends on maintaining 3 things:
1) The proper amount of water in the body
2) The correct proportion of electrolytes and water
3) The proper acid-base balance
What is water’s overall charge?
Neutral (Same number of protons and electrons)
Even though water has an overall neutral charge, is each water molecule polar or non polar? Why?
- Polar
- electrons are asymmetrically distributed making the molecule have a polar charge
Does water have two separate charge ends? what are they?
- Yes
- One end is slightly positive
- The other end is slightly negative
Does oxygen draw electrons close to or away from hydrogen?
-oxygen draws electrons AWAY FROM hydrogen
Water molecules contain what kinds of bonds?
hydrogen
At 37 degrees C, 15% of water molecules are joined to 4 other water molecules as…
“flickering clusters”
What properties are water’s cohesive bondness responsible for?
High surface tension, specific heat, etc
Why can two adjacent water molecules form hydrogen bonds?
because water is polarized
Which is stronger? Covalent or Hydrogen bonds?
Covalent bonds
Which bond is longer? Covalent or Hydrogen bonds?
Hydrogen bonds are longer (.27 nm). Covalent bonds are shorter (.10 nm)
Water is a solvent. What does this mean?
It means many substances dissolve in water. The molecules separate from each other and are each surrounded by water molecules.
Solution
a substance dissolved in a liquid
Solute
the dissolved substance
Solvent
the liquid
Hydrophilic molecule
a substance that dissolves readily
What are hydrophilic molecules composed of?
ions or polar molecules
How do hydrophilic molecules attract water?
through electrical charge effects
Hydrophobic molecules
molecules that are insoluble in water
What kind of bonds do hydrophobic molecules contain?
non-polar bonds
What kind of bonds are water molecules not attracted to?
C-H bonds (hydrocarbons)
Will water molecules surround C-H bonds?
No
What is the largest single constituent of the body?
Water
How much of the total body weight is water?
60%
All fluids in the body are either one of two things?
extracellular fluid or intracellular fluid
Rank the body fluids from highest to lowest
Intracellular > interstitial > plasma (intravascular)
Where is 2/3 of the bodily fluid?
Intracellularly- within the cells
Where is 1/3 of the bodily fluid found?
Extracellularly
80% of the ECF is_______
interstitial fluid
20% of the ECF is_______
blood plasma
Where is the interstitial located?
microscopically between tissue cells
Some of the ECF is known as?
transcellular fluid
What is transcellular fluid?
fluid located between cell layers
Where are some of the transcellular fluid located?
lymph of lymph vessels; cerebrospinal fluid in the brain; synovial fluid in the joints; aqueous humor/vitreous body in the eyes; endolymph/perilymph in the ears; pleural/pericardial/peritoneal fluids between serous membranes; glomerular filtrate in the kidneys
what are endothelial cells
they are simple squamous cells that line the inside (lumen) of blood and lymph vessels.
What are the three fluid compartments of the ECF?
1) Interstitial fluid
2) Blood plasma and lymph
3) Transcellular fluid
When is an animal is fluid balance?
When the amount of water gained each day is equal to the amount of water lost
What does the maintenance of normal fluid balance entail?
1) regulating body water content
2) regulating distribution of water in the ECF and ICF
What are the sources of water intake?
1) Ingested liquid: drinking water
2) Ingested food
3) Metabolic water: byproduct of cellular respiration/electron transport chain
What are the two main sources of body water?
ingested liquids and moist foods
What is preformed water?
ingested liquids and moist foods
Is body fluid volume usually constant? does the amount lost equal the amount gained?
Yes
What are 4 routes of water loss/outtake?
1) Kidneys
2) Skin
3) Lungs
4) Gastrointestinal tract
How do the kidneys lose water?
Excretes most of the water; excretes water in urine
How does the skin lose water?
excretes water as sweat
How do the lungs lose water?
the lungs exhale water vapor
How does the GI lose water?
in the feces
Why is fluid gain not regulated to maintain homeostasis of body water?
because of the formation of metabolic water
What does the level of metabolic water depend on?
depends on the level of cellular respiration which reflects the cell’s demand for ATP
What is the main way to regulate body fluid gain?
by adjusting the volume of preformed water; drinking more or less
Two types of perspiration contribute to water loss to the environment:
1) insensitive perspiration
2) sensible perspiration
Insensitive perspiration
the gradual movement of water across the skin and respiratory tract
Sensible perspiration
the secretory activities of the sweat glands (varies)
Which type of perspiration causes significant water loss?
sensible
Why is water gain needed?
Water gain is required to balance average water losses
How is water gained?
Water is gained by eating, drinking, and metabolic generation
What is metabolic generation of water
it is where water is produced by the cells
Metabolic generation of water usually occurs how and where?
by oxidative phosphorylation, in the mitochondria
recall: oxidative phosphorylation is the metabolic pathway in which cells us enzymes to oxidize nutrients (NADH, FADH2) which release energy (H+ is severed releasing energy) which is then used to reform ATP. At the end of the electron transport chain H2O is created as a bi-product
how are bodily fluids separated?
into compartments by selectively permeable membranes
how are individual cells separated from intracellular fluid and interstitial fluid?
the plasma membrane
how are interstitial fluid and blood plasma separated
the blood vessel wall (made of endothelium)
although fluid is in constant motion, the volume of each fluid compartment remains fairly stable: what is this called?
homeostasis
what does blood do in terms of movement of bodily fluids?
The blood is the vehicle of transport and exchange of materials between body cells and the outside world
where do the nutrients from food ingested go?
they enter the blood for distribution into the tissues throughout the body
where does oxygen enter and go?
enters the lungs and then goes to the blood
waste products generated by cellular metabolism go where?
they diffuse out of the cells and into the blood stream
where do waste products generated by cellular metabolism go after they get into the blood stream?
from the blood they can be
1) excreted into the urine, 2) exhaled by the lungs 3) or follow another route out of the body
what is the go between of intracellular fluid and the blood plasma?
interstitial fluid
the movement of substances between blood plasma and interstitial fluid occurs across what?
capillary walls
Substances enter and leave capillaries in what 3 ways?
1) vesicular transport
2) diffusion
3) bulk flow
Vesicular transport
substances in the blood plasma enter endothelial cell by endocytosis and then exit the cell into the interstitial fluid by exocytosis (only some molecules do this) (ex proteins)
Diffusion
Most molecules move from capillaries to tissue by diffusion
- O2 and CO2 is exchanged between blood and lungs by diffusion
- individual solutes like glucose and amino acids go down their concentration gradient by diffusion
Diffusion exception!
in the brain, the blood-brain barrier blocks diffusion of many substances
what two mechanisms does Bulk Flow consist of?
1) filtration
2) reabsorption
What is Filtration (bulk flow)?
the net movement of materials from the blood to the interstitial fluid
What is reabsorption (bulk flow)?
the net movement of materials from the interstitial fluid to the blood
Arterial end of capillaries (from the heart)
has high hydrostatic pressure
Venus end of capillaries
has low hydrostatic pressure
Filtration predominates at what end of the capillaries?
the arteriolar end
Reabsorption predominates at what end of the capillaries?
the venule end
Which occurs more in the capillaries: filtration or reabsorption?
filtration
Where do fluids go that are not reabsorbed into the blood capilliaries and particles go that escaped from the blood ?
they go to the lymphatic capillaries, move through the lymphatic vessels, and then are emptied into the circulatory system
What is bulk flow?
the movement of water by hydrostatic pressure and osmotic pressure
What two forces control the movement of water from one compartment to another?
1) hydrostatic pressure
2) osmotic pressure
Osmotic pressure is caused by and goes into?
Osmotic pressure is caused by proteins and goes from interstitial into the blood capillary
Hydrostatic pressure is caused by and goes into?
Hydrostatic pressure is caused by blood pressure and goes from the blood capillaries into the interstitial fluid
True or False: any factors that affect the net hyrdostatic or osmotic pressure will alter the distribution of fluids within the ECF
True
What is edema?
the movement of abnormal amounts of water from the plasma to the interstitial fluid.
What is pulmonary edema?
An increase in the blood pressure in the pulmonary capillaries.
True of false: conditions that affect the water balance will also affect the solute concentration
true
What are electrolytes?
compounds that are able to conduct electricity and dissociate into ions in solution
What are the 4 main functions of electrolytes in the body?
1) Body structure/ cell metabolism
2) electrolytes facilitate the osmotic movement of water between fluid compartments
3) Help maintain acid-base balance (H+ concentration)
4) produce/maintain membrane potentials and action potentials
ECF and ICF usually act as?
Distinct entities
The principal ions in the ECF are?
1) Sodium
2) Chloride
3) Bicarbonate
The ICF contains an abundance of:
1) Potassium
2) Magnesium
3) Phosphate
4) Negatively charged proteins
Are the osmolarities of the ECF and ICF the same or different?
The same
How are small differences in the ECF and ICF managed?
By osmosis, because cell membranes are freely permeable to water.
Remember, osmosis is the movement of water through a semipermeable membrane
What regulates fluid movement between the intracellular compartments?
Hydrostatic and osmotic pressure
The interstitial fluid and the hydrostatic pressure within the cells are the equal or different?
they are equal
fluid flow or an imbalance between the interstitial fluid and the intracellular compartment is usually due to what kind of pressure?
osmotic pressure
If there is a decrease in plasma sodium where will the water go? What will cells do?
there will be a net movement of water from the plasma to the interstitial fluid causing the cells to SWELL
when dealing with problems of fluid balance, can transcellular fluid be ignored?
yes, it is usually insignificant to the total body gain or loss, or usually won’t change with rest of body
Osmotic pressure change is usually due to what changes?
1) a change in Na+ concentration
2) a change in K+ concentration
What is the principal cation outside the cell?
Na+
What is the principal cation inside the cell?
K+
What regulates Na+ balance inside the body?
ANP, ADH, and aldosterone
What regulates K+ balance inside the body?
Aldosterone
What is fluid shift?
movement of water from between ECF and ICF
Does fluid shift occur slowly or rapidly? and how long does it take to reach equilibrium?
It occurs rapidly. Takes 30 minutes to an hour to reach equilibrium
Why do fluid shifts occur?
Fluid shifts occur in response to osmolarity changes of ECF
What is osmolarity?
the number of solutes per liter of solution
What happen if osmolarity of the ECF increases?
then the solutes in the ECF increases, water will follow the solutes out of the cell to the ECF causing the cell to shrink (hypertonic solution)
Osmolarity of the ECF will increase if subject loses water from the ECF but retains what?
electrolytes
What happens if osmolarity of the ECF decreases?
then the solutes in the ICF will increase. Water will follow solutes into the cell and the cell will swell (hypotonic to ICF).
The Osmolarity of the ECF will decrease if the subject gains water but does not gain what?
electrolytes
