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Flashcards in Water Balance Deck (83)
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What is interstitial fluid ?

This is the fluid in the spaces between cells


What is osmosis dependent on ? What is osmotic pressure?

The concentration of dissolved particles.... so Osmotic Pressure, which is a measure of the solute concentration


Water balance needs to be highly regulated because

water intake needs to equal water output to maintain homeostasis level with same blood volume and blood pressure. Cells need water to function in metabolism, and water is needed to dissolve substances


What helps to regulate water balance?

Hypothalamus, ADH


What is the percentage of water in adipose, bone, blood and skeletal muscle respectively?

Water is contained in all tissues, with adipose (fat) tissue containing about 10% water, bone about 22% water, blood about 83% water and skeletal muscle about 65% water.


What property of water makes it so useful in human body physiology?

The ability of water to dissolve so many types of substances allows our cells to metabolize the carbohydrates and proteins that our bodies use as food, digest our food, transport waste and control body temperature.


Where is water located in the body?

Water is located in two main compartments of the body. : inside the cells (the intracellular fluid compartment) and outside of the cells (the extracellular fluid compartment). The intracellular fluid (ICF) accounts for about 60% of the fluid in the body which in a 150 lb. (70 kg) adult male consists of about 25 liters. The extracellular fluid (ECF) accounts for about 40% which in a 150 lb. (70 kg) adult male consists of about 15 liters.


What are the two sections of extracellular fluid ?

Extracellular fluid consists of two sections: plasma, the fluid portion of blood which contains about 3 liters (8% of total body water) and interstitial fluid, the fluid in the microscopic spaces between cells which contains about 12 liters (32% of total body water)


Do electrolytes or non electrolytes have a greater effect on the movement of water across semi-permeable membranes?

Electrolytes (ionic solutes which become charged in solution) because when dissolved in water they dissociate into two or more ions. This contributes to the osmolarity of a solution (a measure of the solute concentration) to a greater degree than non electrolytes (which do not dissociate in water). Basically, electrolytes influence the concentration levels, which affects the movement of water. Osmosis is dependent on the solute concentration levels.


Osmosis is dependent on the ........

The concentration of dissolved particles ...the osmolarity and the osmotic pressure


What are the major electrolytes located in the blood plasma and the interstitial fluid?

Na+, HCO3- (bicarbonate) and Cl-


What are the major electrolytes of the intracellular fluid?

K+, Mg+2,and HPO4-2 (hydrogen phosphate).


Does plasma/interstitial fluid or intracellular fluid have the highest protein content?

Blood plasma


Compare the ratio electrolyte and nonelectrolyte content in interstitial fluid, plasma and intracellular fluid.

The nonelectrolyte content (cholesterol, fats, phospholipids and proteins) greatly exceeds the electrolyte content of dissolved materials in all 3 of these compartments constituting 60% in interstitial fluid, 90% in blood plasma and 97% in intracellular fluid.


Track the movement of fluids between intracellular, blood plasma and interstitial compartments and what pressures affect this?

The movement of fluid between compartments occurs according to hydrostatic and osmotic pressures. Transfer from blood plasma to interstitial fluid occurs at the capillaries with hydrostatic pressure driving fluid from blood plasma to the interstitial compartment and osmotic pressure driving fluid from the interstitial fluid to blood plasma. Fluid flows freely in both directions between the interstitial and intracellular compartments driven by osmotic pressure. There is also a flow of fluid from the interstitial compartment into the lymph capillaries due to osmotic pressure.




What is the ultimate, universal , all encompassing, equation of water balance?

Water intake = water output The amount of water one takes in each day must equal the amount of water one loses each day to maintain water balance.


About how much water do humans need every day to maintain water balance?

Humans ingest or produce about 2500 ml of water each day with a majority of this water, 1500 ml, being ingested in fluid form. The other 1000 ml of water is either ingested by food or a very small amount is produced by metabolic reactions in the body. Humans also lose about 2500 ml of water each day with the majority, 1500 ml, being lost by urine excretion. The other 1000 ml is lost through feces, sweat, and respiration.


Water Uptake - where do our fluids come from?


What closely regulates water intake and output?

The hypothalamic thirst mechanism and Anti-Diuretic hormone (ADH)




How does the thirst center and ADH respond to changes in blood volume and osmolarity?

A decrease in plasma volume or increase in plasma osmolarity (especially that of Na+), activates the thirst center which stimulates the need to drink. At the same time ADH is released, causing the kidneys to conserve water by releasing more concentrated urine. Conversely, an increase in plasma volume or decrease in plasma osmolarity, inhibits the thirst center and ADH release, causing the kidneys to release large volumes of dilute urine


What happens to the body during dehydration

The water output has significantly exceeded the water intake in that the loss of water from the plasma and interstitial fluid causes an osmotic flow of water from the intracellular compartment.  This can occur through excessive vomiting, prolonged diarrhea, heavy sweating, extreme blod loss, severe burns, diabetes mellitus and diabetes insipidus. Symptoms include decreased urination, disorientation, dry reddened skin, fever, thickened mucus, thirst and weight loss. Electrolytes are also lost in addition to water during dehydration.


What happens to the body during water intoxication?

The plasma and interstitial fluid become diluted (an abundance of water over solutes) and this causes an osmotic flow of water into the intracellular compartment, causing cells to swell, which can lead to cerebral swelling, muscle cramping, nausea and vomiting due to metabolic disturbances, which if not quickly corrected can lead to convulsion, coma and death.


What does the treatment for water intoxification involve?

Correction of this condition involves intravenous treatment with hypertonic NaCl solution (saline) which pulls the excess water out of the cells.



What is edema?

Tissue swelling due to excess accumulation of fluid in the interstitial compartment caused by fluid flow from the bloodstream due to high blood pressure because of vessel blockages, congestive heart failure or high blood volume due to retention of Na+ or from any condition which prevents return of fluid to the bloodstream such as unusually low plasma protein levels because of protein malnutrition, liver disease or kidney disease. Both increased fluid flow from the bloodstream and decreased return to the bloodstream cause excessive fluid buildup in the interstitial compartment resulting in diminished tissue function due to the greater distance that the nutrients and oxygen must travel. The most serious effect, however, is that of the diminished efficiency of the circulatory system caused by the lower blood pressure and blood volume due to the loss of water from the blood serum compartment.


Describe the movement nutrients, wastes, CO2, O2 into and out of the lungs, GI tract, cells and kidneys


What functions does salt have in the body?

Bone metabolism, respiratory functions, pH balance, neuron signal activation and osmotic fluid movement


What is the most abundant cation in the plasma and interstitial fluid?


present as NaHCO3 (sodium bicarbonate) and NaCl (sodium chloride)

present at ten times the concentrations of the total of the other significant anions, thereby exerting the greatest influence on electrolyte (and fluid) balance.

Remember that when salt is absorbed, water must also be absorbed to maintain osmotic pressure from which comes the familiar statement "water follows salt".



Water follows ____________


This is important because Na+ is the most abundant ion in the body, which means that its presence and concentration influences the movemetn of water.


What are the salts with the greatest physiological importance?

Na+, K+, Ca+2 and Mg+2.


Most body salts are obtained from ingested foods and fluids and are lost by way of defecation, sweating and urination.



What are the 3 ways through which  sodium (and consequently water) balance  is maintained?

Aldosterone, Cardiovascular barocepters, and ADH