Fluid, Electrolytes, and Acid-Base Flashcards
What is a body fluid?
any substance, usually a liquid, that is produced by the body and consists of water and dissolved solutes
What makes up over half of the mass of the adult body?
Body fluids
What are the two “compartments” of body fluids (separated by a barrier)?
Intracellular (Cytosol) and Extracellular (Interstitial fluid, includes lymph, CSF, pleural, serous, etc, and blood plasma)
When does fluid balance occur?
When the required amount of water and solutes are present and correctly spread amongst the “compartments”
What percentage of total body mass does water account for?
45-75%
What allows for constant water and solute exchange between compartments?
Processes such as filtration, reabsorption, diffusion and osmosis
What is an electrolyte?
An inorganic compound that dissociates into ions in H2O
What is an ion
An atom or molecule with a net electrical charge due to a loss or gain of electrons
What is the main source of water gain?
Ingestion
What is another source of water gain?
Metabolic water can be gained during aerobic respiration and dehydration synthesis
How is water lost in the kidneys?
Excrete the majority of water in urine
How is water lost in the skin?
Evaporation by insensible and regular perspiration
How is water lost from the lungs?
Exhaling water vapor
How is water lost through the GI system?
Water elimination as feces
The quantity of metabolic water created is directly proportional to what?
the level of aerobic respiration (more ATP produced = more water produced)
What is dehydration?
water loss is greater than water gain (decrease in volume and increase in osmolarity)
What creates an urge to drink when the body is dehydrated?
The thirst center in the hypothalamus
What different triggers exist that activate the thirst center and create the urge to drink?
- Increased activity from osmoreceptors in the hypothalamus
- Volume receptors in the atria
- Baroreceptors in blood vessels
- Angiotensin II
- Neurons in the mouth detect decreased salivary slow
What is the main function for eliminating excess water and solutes?
Via excretion in the urine
How do the kidneys regulate water loss in urine?
by increasing or decreasing the reabsorption of Na+ and Cl-
What hormones are involved in regulating water and solute loss?
*ADH (water)
*Aldosterone (solute)
*ANP (solute)
What is Antidiuretic Hormone (ADH)?
*The primary hormone involved in regulating water loss
*When the thirst center is triggered it increases
the synthesis and release of ADH
*Promotes water reabsorption by increasing the water permeability in the principal cells of
the tubule and duct of the DCT
*Other factors stimulate the release of ADH: Atrial volume receptors, baroreceptors in the BV, pain, nausea, and stress
What is aldosterone?
*decreased blood volume or Na+ deficiency in plasma trigger the RAAS
* Increases Na+ reabsorption in the DCT and ducts
What is Atrial Natriuretic Peptide (ANP)?
- Stretch receptors in the atria trigger the release of ANP
- Promotes Na+ excretion in the urine (water follows sodium)
- Slows the release of renin (and therefore aldosterone
When there is increased osmolarity of ECF what happens to the fluid?
Turns the fluid hypertonic – Cells shrink
What can happen if ECF stays hypertonic for an extended period of time?
it can cause confusion, convulsions, coma, or death
When there is decreased osmolarity of ECF what happens to the fluid?
Turns the fluid hypotonic – Cells swell
What is water intoxication?
A state in which excessive body water causes cells to swell dangerously
What functions do electrolytes have in the body?
- Regulate osmosis of water between fluid compartments
- Maintain the acid-base balance required for cell function
- Carry electrical current (production of action potentials)
- Cofactors needed for optimal enzyme activity
What is an anion?
Negatively charged ion
What is a cation?
Positively charged ion
What is the main difference between blood plasma and interstitial fluid?
Blood plasma contains a higher amount of protein anion, intracellular fluid has a much higher concentration of K+, HPO42-, and proteins
What are the two most abundant ions in extracellular fluid?
Na+ and Cl-
What is the most abundant ion in ECF?
Na+, accounting for 90% of EC cations
What is normal blood plasma concentration of sodium
136-148mEq/L
What concentration of Na+ would be considered hyponatremia?
Na+ <136mEq/L
What concentration of Na+ would be considered hypernatremia?
Na+ >148mEq/L
What is Na+ responsible for?
Generation of action potentials in neurons and muscle fibers
What are Na+ levels in the blood regulated by?
Aldosterone, ADH, and ANP
What is the most abundant anion in extracellular fluid?
Cl-
What is the role of Cl-?
*Aids in maintaining the balance of anions in fluid
*HCO3- plays a major role in the elimination of CO2, Cl- is exchanged for HCO3- to maintain the anion balance
What helps regulate Cl- balance?
ADH regulates Cl- balance because it regulates water loss in urine, Cl- typically follows Na+
What is the most abundant cation in intracellular fluid?
K+, 140mEq/L
What is the role of K+?
Helps regulate pH levels and heavily responsible in maintaining resting membrane potential and in the repolarization phase of action potentials
What regulates blood plasma concentration of K+?
Regulated by aldosterone
What is a normal concentration of K+?
3.5-5mEq/L
What concentration of K+ would be considered hyperkalemia?
K+ >5mEq/L
What concentration of K+ would be considered hypokalemia?
K+ < 3.5mEq/L
What is the second most abundant ECF anion?
HCO3-
What is HCO3- responsible for?
Heavily responsible for CO2 elimination in maintaining acid-base balance
How are HCO3- levels regulated?
Kidneys can synthesize and release HCO3- into the blood when needed, or secrete more into urine if levels are too high
What happens when CO2 released during cellular metabolism combines with H2O?
Forms carbonic acid (H2CO3) which then dissociates into H+ and HCO3-
What is a normal level of HCO3-?
22-26mEq/L
What is the most abundant mineral in the body?
Ca2+ due to the amount stored in bone
What does Ca2+ play a role in?
blood clotting, neurotransmitter release, muscle tone and contractility, and excitability of nervous and muscle tissue
What are low levels of Ca2+ regulated by?
Mainly regulated by parathyroid hormone
What are the functions of magnesium?
-Aids in the metabolism of carbs and proteins.
-Involved in synaptic transmission, cardiac function, neuromuscular activity
What is an acid?
A substance that dissociates into one or more hydrogen ions (H+) and one or more anions - aka a proton donor
What is a base?
A substance that dissociates into one or more hydroxide ions (OH-) and one or more cations - removes H+ from a solution – aka proton acceptor
What is pH?
the measure of acidity and alkalinity in a solution
What does a pH = 7 mean?
neutral (pure H2O)
What does a pH > 7.0 mean?
basic (alkaline) or more OH- than H+
What does a pH < 7.0 mean?
acidic or more H+ than OH-
What should the pH of arterial blood be to maintain homeostasis?
7.35-7.45
What are the three major mechanisms for the elimination of H+ from the body?
Buffer Systems, Exhalation of CO2, and Kidney Excretion of H+
How does a buffer system work to eliminate excess H+?
bind to excess H+. Temporary increase in pH but doesn’t remove H+ from the body
How does exhalation of CO2 work to eliminate excess H+?
increased RR and depth to eliminate more CO2 thus decreased blood carbonic acid (H2CO3) - raises pH
What does the protein buffer system do?
-Can buffer both acids and bases
-Important in regulating the pH level within RBCs during gas exchange - Hgb is the protein involved
-
What are the 2 ways the protein buffer system can work?
*Release a H+ when pH rises (H+ can than react with excess OH- to form water)
*Pick up any excess H+ at the other end of the chain when pH drops
How does the Bicarbonate Buffer System work?
-Excess H+ can be picked up by HCO3- and forms H2CO3 (which then dissociates into H2O and CO2 to be exhaled)
-Decreased H+ causes carbonic acid to dissociate into H+ and HCO3-
How does exhalation of CO2 effect pH?
*Because CO2 and H2O form H2CO3, CO2 directly impacts pH levels in the body
* H2CO3 can be eliminated by exhaling CO2
* Changes in the rate and depth of breathing can alter the pH of body fluids very rapidly
* Increased RR —> decreased CO2 —> H+ drops —> pH rises
* Decreased RR —> increased CO2 —> H+ rises —> pH drops
What is the process of the respiratory negative feedback loop that effects pH?
*Increased acidity (low pH) or elevated CO2 levels are detected by chemoreceptors in the medulla oblongata (central) and the carotid and aortic arteries (peripheral)
*Stimulates the respiratory center in the medulla to increase the rate and depth of breathing (exhale more CO2) until pH levels return to normal
* Process works in the opposite as well - decreased CO2 or increased alkalinity (high pH) slow the respiratory drive down until homeostasis is achieved
What happens in kidney elimination of H+?
*The kidneys have the ability to excrete excess H+ when pH is low and excess HCO3- when pH is high
*The H+ that is excreted into the tubules is often buffered (combined) with other ions to prevent the reabsorption of H+
What pH would be considered acidosis?
pH < 7.35
What physiological effects can occur in acidosis?
CNS depression via depression of synaptic
transmission which can cause disorientation, coma, lethargy, death
What pH would be considered alkalosis?
pH > 7.45
What physiological effects can occur in alkalosis?
Major physiological effects include: over-excitability of CNS and PNS causing nervousness, muscle spasms, convulsions, death.
What happens if a person has altered pH due to metabolic causes?
the respiratory system can compensate by hyper or hypoventilation – fast change
What happens if the altered pH is due to a respiratory cause?
the renal system must compensate by changes in H+ secretion and HCO3- reabsorption - slow change
What levels would be seen in respiratory acidosis?
pH < 7.35
CO2 > 45mmHg
HCO3- –> 22-26mEq/L
What levels would be seen in respiratory alkalosis?
pH > 7.45
CO2 < 35mmHg
HCO3- –> 22-26mEq/L
What levels would be seen in metabolic acidosis?
pH < 7.35
CO2 —> 35-45mmHg
HCO3- < 22mEq/L
What levels would be seen in metabolic alkalosis?
pH > 7.45
CO2 —> 35-45mmHg
HCO3- > 26mEq/L